B.Pharm 7th Semester Novel Drug Delivery System Important Question Answer
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Novel Drug Delivery System Very Short Question Answers [2 Marks]
1. Define the term Microencapsulation and Microcapsules.
Microencapsulation is a process in which active substances are enclosed within a coating to form small capsules ranging from 1 to 1000 μm.
Microcapsules are small spherical particles that contain a core substance surrounded by a polymeric shell or coating.
2. Explain the functions of the various structural components of Liposomes.
Phospholipid bilayer: Forms the basic structure, encapsulates hydrophilic drugs inside and embeds lipophilic drugs in the bilayer.
Cholesterol: Enhances membrane stability and rigidity.
Aqueous core: Encloses hydrophilic drugs.
Surface modifiers (e.g., PEG): Improve circulation time and targeting.
3. Mention the applications of Monoclonal antibodies in targeted drug delivery.
Targeting specific cancer cell markers (e.g., HER2 in breast cancer).
Delivering cytotoxic drugs directly to diseased cells.
Used in immunotherapy and diagnostic imaging.
4. Define the term ‘permeation enhancers’ with examples.
Substances that temporarily increase the permeability of skin or mucosa to facilitate drug absorption.
Examples: Oleic acid, ethanol, DMSO, sodium lauryl sulfate.
5. Mention basic components of Transdermal drug delivery systems.
Drug
Polymer matrix or reservoir
Backing membrane
Adhesive layer
Release liner
6. Explain Spray drying/spray congealing method.
Spray drying: Drug-polymer solution is sprayed into hot air, solvent evaporates, leaving dry particles.
Spray congealing: Molten drug or polymer is sprayed into cool air, causing solidification into microcapsules.
7. Mention the advantages and disadvantages of Buccal drug delivery system.
Advantages: Avoids first-pass metabolism, prolonged release, easy administration.
Disadvantages: Limited permeability, small dosage capacity, irritation risk.
8. Define Niosomes and Nanoparticles.
Niosomes: Non-ionic surfactant-based vesicles used for drug delivery.
Nanoparticles: Solid colloidal particles (10–1000 nm) used for controlled and targeted drug delivery.
9. Define Hydrodynamic pressure activated DDS.
Drug delivery systems that release the drug in response to internal pressure changes in the GI tract, aiding in controlled release.
10. Mention different factors affecting transmucosal permeability.
Lipophilicity
Molecular size
pH of the environment
Use of permeation enhancers
Enzymatic degradation
11. State two major physicochemical properties of drugs relevant to controlled release formulations.
Aqueous solubility
Partition coefficient (lipophilicity)
12. Mention the role of polymers in formulation of controlled release drug delivery systems.
Control drug release rate
Provide structural integrity
Enhance bioadhesion and stability
13. State the principles of bioadhesion.
Bioadhesion is the ability of a drug delivery system to adhere to biological tissues (e.g., mucosal membranes) via molecular interactions like hydrogen bonding, van der Waals forces, or electrostatic forces.
14. Name the factors affecting transmucosal permeability.
(Same as Q10)
Molecular weight
Lipophilicity
pH and ionization
Membrane thickness
Use of enhancers
15. State the working principles of various permeation enhancers.
Disrupt lipid bilayer of membrane
Modify protein structure
Increase solubility of drug
Extract lipids from the stratum corneum
16. Define metered dose inhalers.
Devices that deliver a specific dose of medication to the lungs in the form of a short burst of aerosolized medicine.
17. State the functions of the various structural components of liposomes.
(Repeat of Q2)
18. Mention the applications of monoclonal antibodies on targeted drug delivery.
(Repeat of Q3)
19. Name the intraocular barriers to ophthalmic drug delivery.
Corneal barrier
Blood-aqueous barrier
Blood-retinal barrier
Tear dilution and drainage
20. State the limitations of the use of IUDs.
Risk of infection
Uterine perforation
Expulsion
Ectopic pregnancy risk
Menstrual irregularities
21. Define microparticles.
Microparticles are small spherical particles (1–1000 μm) composed of natural or synthetic polymers used to encapsulate drugs for controlled release.
22. Define microencapsulation.
(Repeat of Q1)
23. Classify GRDDS.
Floating systems
Swelling systems
Bioadhesive systems
High-density systems
Osmotically controlled systems
24. Name four methods of microencapsulation along with examples.
Coacervation-phase separation (e.g., gelatin microcapsules)
Spray drying (e.g., Vitamin C microcapsules)
Interfacial polymerization (e.g., Polyamide microcapsules)
Solvent evaporation (e.g., PLGA microspheres)
25. What are monoclonal antibodies?
Monoclonal antibodies are identical immunoglobulins produced by a single clone of B cells, designed to bind specifically to a single antigen site.
26. Polymer Matrix Diffusion-Controlled DDS.
In this system, the drug is dispersed within a polymer matrix, and release occurs via diffusion through the matrix (e.g., ethylcellulose-based tablets).
27. Define Hydrodynamic pressure activated DDS.
(Repeat of Q9)
28. Factors considered while development of nasal drug delivery system.
Drug solubility and stability
pH and osmolarity
Nasal mucosa condition
Absorption enhancers
Formulation viscosity
29. Give biomedical application of Nasal DDS.
Systemic delivery of peptides (e.g., insulin)
CNS drug delivery (e.g., for Alzheimer’s)
Vaccination (e.g., influenza nasal vaccines)
30. Classify polymers.
Natural: Chitosan, Gelatin
Synthetic: PLA, PLGA, PVA
Biodegradable: Polylactide, polyglycolide
Non-biodegradable: EVA, PMMA
Novel Drug Delivery System Short Question Answers [5 Marks]
1. Explain in brief the various methods to overcome ocular barriers for effective drug delivery.
Ocular drug delivery faces challenges such as tear turnover, blinking, drainage, and static barriers like the corneal epithelium and blood-ocular barriers. Several methods have been developed to overcome these issues. One approach involves using mucoadhesive polymers such as chitosan and carbopol to increase the contact time of the formulation with the ocular surface. In situ gels, which convert from liquid to gel upon administration due to temperature or pH changes, also prolong residence time. Ocular inserts like Ocusert can deliver drugs in a sustained manner by placing solid devices into the conjunctival sac. Colloidal carriers such as liposomes, niosomes, and nanoparticles help in bypassing barriers and ensuring controlled and targeted drug release. Permeation enhancers like EDTA can transiently open tight junctions to allow drugs to penetrate. Advanced methods like iontophoresis and microneedles help in enhancing penetration by using physical forces. These strategies improve ocular bioavailability, reduce dosing frequency, and enhance patient compliance. However, care must be taken to minimize irritation and ensure the safety of the eye.
2. Discuss the development and applications of IUDs in pharmaceutical drug delivery.
Intrauterine Devices (IUDs) are widely used for contraceptive purposes and have evolved into sophisticated drug delivery systems. The first IUDs were non-medicated and relied solely on a foreign-body reaction to prevent pregnancy. Over time, medicated IUDs were developed for more effective and long-term use. Copper-releasing IUDs (e.g., Copper T) interfere with sperm mobility and fertilization. Hormonal IUDs, such as those releasing levonorgestrel, offer additional benefits like reduced menstrual bleeding and endometrial thinning. These IUDs act locally and provide sustained drug release for 3–5 years. Pharmaceutical IUDs can also be utilized to deliver drugs for gynecological disorders like endometriosis, uterine fibroids, or hormone replacement therapy. Advantages of IUDs include site-specific action, avoidance of hepatic first-pass metabolism, prolonged drug release, and high patient compliance. Their limitations include risk of pelvic infections, uterine perforation, and device expulsion. Despite these limitations, the use of IUDs as a novel drug delivery platform continues to expand beyond contraception, offering targeted delivery of therapeutic agents directly to the uterus.
3. Mention the various formulation approaches for gastro-retentive drug delivery systems. Discuss any one method.
Gastro-retentive drug delivery systems (GRDDS) aim to prolong the residence time of dosage forms in the stomach, enhancing drug absorption and bioavailability, especially for drugs absorbed in the upper GIT. Common approaches include:
Floating systems: These are low-density systems that remain buoyant on gastric fluid.
Swelling/Expandable systems: These swell after ingestion, increasing in size to prevent passage through the pylorus.
Bioadhesive systems: These adhere to gastric mucosa, resisting gastric emptying.
High-density systems: Designed to sink and settle in the stomach.
Mucoadhesive systems: Stick to the stomach lining and release drug slowly.
Floating drug delivery systems are the most widely used GRDDS. These systems use gas-generating agents (e.g., sodium bicarbonate) that react with gastric acid to produce CO₂, which keeps the dosage form afloat. Non-effervescent types use swellable polymers like HPMC to maintain buoyancy. Drugs like ciprofloxacin and propranolol are formulated as floating tablets. Floating systems improve gastric retention, allow site-specific drug release, and enhance bioavailability. However, they are not suitable for drugs that are unstable in gastric pH or irritate the gastric mucosa.
4. Define targeted drug delivery system and explain the various drug targeting approaches.
A targeted drug delivery system (TDDS) is designed to deliver the drug precisely to the site of action, reducing systemic side effects and improving therapeutic outcomes. It ensures that the drug reaches only the intended tissues or cells, particularly useful in diseases like cancer, infections, and autoimmune disorders.
Drug targeting approaches are classified into several types:
Passive Targeting: Utilizes the natural biodistribution properties of the drug or carrier, such as the Enhanced Permeability and Retention (EPR) effect in tumors.
Active Targeting: Involves modifying the drug carrier with ligands or monoclonal antibodies that bind to specific receptors overexpressed on target cells.
Physical Targeting: Uses external stimuli like magnetic fields, ultrasound, pH, or temperature to trigger drug release at the desired site.
Stimuli-Responsive Delivery: Drug carriers respond to internal physiological conditions such as pH or enzyme presence.
Dual Targeting: Combines passive and active strategies for better selectivity.
Examples include liposomal doxorubicin for cancer treatment and antibody-drug conjugates (ADCs) for targeted chemotherapy. TDDS can reduce dosing frequency, enhance efficacy, and minimize drug wastage.
5. Discuss briefly Nebulizer and Metered Dose Inhalers.
Nebulizers and Metered Dose Inhalers (MDIs) are two major types of pulmonary drug delivery devices, used mainly for the treatment of respiratory diseases like asthma, COPD, and bronchitis.
Nebulizers are devices that convert liquid medications into aerosol or fine mist for inhalation. They operate using compressed air (jet nebulizers) or ultrasonic vibrations (ultrasonic nebulizers). These are especially beneficial for children, the elderly, and critically ill patients who cannot coordinate their breathing. They allow administration of higher doses and are suitable for long-term therapy. However, they are bulky, time-consuming, and require regular cleaning.
Metered Dose Inhalers (MDIs), on the other hand, are portable, pressurized canisters that deliver a fixed amount of drug per actuation. They use a propellant, such as HFA (hydrofluoroalkane), to expel the medication in aerosol form. MDIs are fast-acting, convenient, and ensure minimal drug wastage when used correctly. Their main limitation is that proper technique and coordination are required for effective drug delivery, and spacers may be needed to assist in proper inhalation. Overall, both devices serve critical roles in pulmonary therapy with distinct advantages and limitations.
6. Define and classify polymers and explain applications of polymers.
Polymers are large molecules composed of repeating structural units known as monomers. They play a critical role in pharmaceutical formulations, particularly in the development of novel drug delivery systems by modifying drug release and enhancing stability.
Classification of polymers can be based on different criteria:
Origin:
Natural: Gelatin, Chitosan, Alginate
Synthetic: Polyvinyl alcohol (PVA), Polylactic acid (PLA), Polyglycolic acid (PGA)
Biodegradability:
Biodegradable: PLGA, chitosan
Non-biodegradable: Ethyl cellulose, EVA
Functionality:
Matrix formers: HPMC, EC
Bioadhesive agents: Carbopol, PVP
Coating agents: CAP (cellulose acetate phthalate)
Applications of polymers in drug delivery systems include:
Controlled release formulations: Polymers control the drug release rate (e.g., HPMC in matrix tablets).
Mucoadhesive delivery: Enhance drug residence time at mucosal surfaces.
Nanoparticles and microspheres: Biodegradable polymers like PLGA are used to encapsulate drugs for targeted delivery.
Transdermal systems: Used in adhesive layers and rate-controlling membranes.
Ocular inserts and implants: Provide sustained release in sensitive sites.
Polymers thus enhance bioavailability, stability, and targeting efficiency of drugs in NDDS.
7. Explain the significance and limitations of naso-pulmonary drug delivery systems.
Naso-pulmonary drug delivery systems are routes used to deliver drugs via the nasal or pulmonary pathway. These systems are highly significant due to their non-invasive nature, large surface area for absorption, and potential for both local and systemic delivery.
Significance:
Bypasses first-pass metabolism, increasing bioavailability.
Allows rapid onset of action due to rich vascularization.
Suitable for systemic delivery of peptides and proteins (e.g., insulin, calcitonin).
Offers direct nose-to-brain delivery through the olfactory region, bypassing the blood-brain barrier.
Used in vaccination, local treatment of asthma, COPD, and even for CNS drugs.
Limitations:
Mucociliary clearance can remove the drug before absorption.
Enzymatic degradation in the nasal cavity may limit protein and peptide drug delivery.
Limited to low-dose drugs due to small administration volume.
Formulations can cause nasal irritation, congestion, or discomfort.
Humidity and breathing patterns can affect drug deposition in pulmonary systems.
Despite these limitations, naso-pulmonary delivery is an evolving area in NDDS, especially for emergency medication, brain targeting, and vaccination platforms.
8. Classify polymers on functional basis.
Polymers can be classified based on their functional role in pharmaceutical formulations:
Matrix-forming polymers:
Used to embed the drug and control its release by diffusion or erosion.
Examples: Hydroxypropyl methylcellulose (HPMC), Ethyl cellulose.
Bioadhesive polymers:
Enhance adhesion to mucosal surfaces, increasing drug retention time.
Examples: Carbopol, Chitosan, Polycarbophil.
Rate-controlling membrane polymers:
Used in reservoir systems to regulate drug diffusion across the membrane.
Examples: Ethylene-vinyl acetate (EVA), Silicone rubber.
Coating polymers:
Protect the drug from environmental conditions or modify release (e.g., enteric coating).
Examples: Cellulose acetate phthalate, Eudragit.
Swelling/Expandable polymers:
Used in gastro-retentive systems to swell and prevent gastric emptying.
Examples: Polyethylene oxide (PEO), Guar gum.
These polymers are crucial in the design of NDDS like transdermal systems, mucoadhesive tablets, microspheres, and nanoparticles, where they ensure controlled, targeted, and site-specific drug release.
9. Write a brief note on transmucosal permeability and formulation considerations for buccal drug delivery systems.
Transmucosal permeability refers to the ability of a drug to cross the mucosal barrier (e.g., buccal, nasal, rectal) to reach systemic circulation. The buccal mucosa, located inside the cheek, is an attractive site for drug delivery due to its accessibility, rich blood supply, and ability to bypass hepatic first-pass metabolism.
Factors influencing permeability include:
Drug lipophilicity and molecular weight.
pKa and ionization status in oral pH.
Use of permeation enhancers like bile salts or surfactants.
Formulation considerations for buccal systems:
Mucoadhesive polymers like carbopol or HPMC to ensure prolonged contact.
Enzyme inhibitors to prevent degradation of peptides/proteins.
Backing layer in unidirectional systems to prevent drug loss.
pH modifiers to maintain an optimal microenvironment for drug absorption.
Controlled release matrices to sustain drug delivery over time.
Buccal formulations include tablets, films, patches, and gels, offering advantages like ease of administration, rapid absorption, and avoiding GI degradation. However, challenges like limited surface area, irritation, and saliva washout must be addressed.
10. Describe the formulation approaches for gastro-retentive drug delivery systems.
Gastro-retentive drug delivery systems (GRDDS) are designed to prolong the residence time of a dosage form in the stomach, allowing drugs with a narrow absorption window or unstable in intestinal pH to be absorbed effectively. The primary goal is to maintain the formulation in the gastric region for a prolonged time, enhancing bioavailability and therapeutic efficacy.
Formulation Approaches:
Floating systems: These are less dense than gastric fluid and remain buoyant. They are classified into:
Effervescent systems: Generate CO₂ using sodium bicarbonate.
Non-effervescent systems: Use swellable polymers like HPMC.
Swelling or expandable systems: Increase in size after administration, preventing passage through the pylorus.
Bioadhesive systems: Stick to the stomach lining and resist gastric emptying.
High-density systems: Formulations with density >1.5 g/cm³ that sink and settle in the stomach.
Magnetic systems: Use an external magnet to retain the system in the stomach.
Formulation considerations include polymer selection, gas-generating agents, drug solubility, and gastric emptying rate. GRDDS are ideal for drugs like ciprofloxacin, metformin, and riboflavin.
11. Explain the various drug targeting approaches.
Drug targeting refers to delivering drugs specifically to the site of action, minimizing side effects and improving efficacy. It plays a vital role in treating diseases like cancer, infections, and inflammation, where nonspecific distribution can lead to toxicity.
Approaches to drug targeting include:
Passive Targeting: Utilizes natural physiological characteristics such as the Enhanced Permeability and Retention (EPR) effect seen in tumors. Nanocarriers accumulate at the tumor site due to leaky vasculature and poor lymphatic drainage.
Active Targeting: Involves modifying drug carriers with ligands like antibodies, peptides, or folic acid that bind specifically to receptors overexpressed on target cells. This ensures selective cellular uptake.
Physical Targeting: Uses external triggers such as magnetic fields (in magnetic nanoparticles), temperature (thermo-sensitive polymers), ultrasound, or light to localize and activate drug release at the target site.
Stimuli-Responsive Targeting: Drug release is triggered by internal stimuli such as pH, redox potential, or specific enzymes present in the pathological site (e.g., cancer microenvironment).
Dual Targeting: Combines passive and active approaches to improve specificity and therapeutic outcomes.
Examples: Liposomal doxorubicin (Doxil) uses passive targeting for cancer; monoclonal antibody-drug conjugates (e.g., Trastuzumab emtansine) employ active targeting. These approaches improve drug bioavailability, reduce systemic toxicity, and enhance therapeutic response.
12. State and explain the significance and limitations of naso-pulmonary drug delivery systems.
Naso-pulmonary drug delivery systems are non-invasive routes used to deliver drugs either via the nasal cavity or lungs. They are significant for both local and systemic delivery, especially for drugs that require rapid action or bypassing first-pass metabolism.
Significance:
Bypasses first-pass effect, enhancing bioavailability of drugs like peptides and proteins.
Rapid onset of action due to rich vascularization in nasal and pulmonary regions.
Ideal for CNS drug delivery via olfactory nerves in nasal route (nose-to-brain delivery).
Suitable for emergency therapy (e.g., naloxone, epinephrine).
Pulmonary route is preferred for asthma, COPD, and even vaccine delivery.
Limitations:
Mucociliary clearance in nasal cavity and lung defense mechanisms can expel drugs quickly.
Enzymatic degradation in the nasal mucosa limits protein/peptide delivery.
Volume restriction: Only small doses (100–200 µL) can be administered nasally.
Particle size and device design are critical for effective lung deposition.
Nasal formulations may cause local irritation or discomfort.
While these routes offer significant therapeutic advantages, careful formulation design, selection of appropriate permeation enhancers, and delivery devices are crucial to overcome their limitations and maximize therapeutic outcomes.
13. Explain in brief the various methods to overcome ocular barriers for effective drug delivery.
Ocular drug delivery is hindered by several barriers, including tear turnover, corneal epithelium, conjunctival clearance, and blood-ocular barriers. These barriers lead to poor bioavailability and therapeutic efficacy, especially for topically applied drugs. Therefore, various strategies are employed to improve ocular drug delivery.
Viscosity Enhancers: Polymers like HPMC or carbopol increase the viscosity of eye drops, thus prolonging residence time and reducing drainage.
Mucoadhesive Polymers: Polymers like chitosan and polycarbophil adhere to the ocular surface and increase contact time, enhancing absorption.
In Situ Gels: These are liquid upon instillation and convert to gel due to pH or temperature changes. Gellan gum and poloxamers are common examples.
Ocular Inserts: Solid dosage forms placed in the conjunctival sac for sustained release (e.g., Ocusert with pilocarpine).
Colloidal Carriers: Liposomes, niosomes, and nanoparticles can encapsulate both hydrophilic and lipophilic drugs, providing controlled and targeted delivery.
Permeation Enhancers: Agents like EDTA or surfactants can increase drug permeability by loosening tight junctions.
Iontophoresis and Microneedles: Physical methods that enhance drug penetration across ocular tissues using electrical currents or micro-channels.
These strategies aim to enhance drug residence, improve corneal penetration, and reduce dosing frequency, thereby enhancing therapeutic efficacy and patient compliance.
14. Write a brief note on the development and applications of intrauterine devices (IUDs).
Intrauterine Devices (IUDs) are small, T-shaped drug delivery systems inserted into the uterus for long-term, controlled drug release. Initially developed for contraception, IUDs have evolved into advanced localized drug delivery systems.
Development:
Early IUDs were non-medicated and worked by creating a local foreign-body reaction.
Later, copper IUDs (e.g., Copper-T) were introduced, offering enhanced contraceptive effects.
Hormonal IUDs, such as levonorgestrel-releasing devices (e.g., Mirena), were developed to deliver hormones locally over a period of 3–5 years.
Applications:
Primarily used for contraception, offering high efficacy and patient compliance.
Deliver hormones for treating gynecological conditions like endometriosis and menorrhagia.
Can be designed for targeted uterine therapy, potentially for delivering anti-inflammatory or anticancer drugs.
Reduces systemic side effects and avoids first-pass metabolism, making it ideal for localized therapy.
Advantages:
Long-acting and reversible.
Local action with minimal systemic exposure.
High patient adherence.
Limitations:
Risk of pelvic infections, uterine perforation, and device expulsion.
Not suitable for women with active pelvic inflammatory disease.
Despite limitations, IUDs represent an effective, site-specific platform in female reproductive health and localized drug delivery.
15. Define targeted drug delivery system and explain its approaches.
A Targeted Drug Delivery System (TDDS) refers to a system designed to deliver the drug specifically to the desired site of action with minimal exposure to non-target tissues. This leads to enhanced therapeutic efficacy and reduced side effects.
Approaches to Targeted Delivery:
Passive Targeting: Exploits physiological conditions such as the EPR (Enhanced Permeability and Retention) effect in tumors, where nanoparticles accumulate due to leaky vasculature.
Active Targeting: Involves surface modification of the drug carrier with ligands, antibodies, or peptides that bind selectively to overexpressed receptors on target cells (e.g., folate receptor targeting in cancer).
Physical Targeting: Uses external stimuli such as magnetic fields, ultrasound, light, or heat to direct the drug to a specific area and trigger its release.
Stimuli-Responsive Targeting: The carrier releases the drug in response to internal triggers like pH changes, redox conditions, or specific enzymes present at the target site.
Dual Targeting: Combines both passive and active mechanisms to maximize delivery precision.
Examples: Liposomal amphotericin B, monoclonal antibody-drug conjugates (e.g., Kadcyla), and magnetic nanoparticle-based carriers.
These approaches are highly valuable in the treatment of cancers, infections, and inflammatory diseases, where conventional therapy may fail due to nonspecific distribution and side effects.
16. What are intraocular barriers? Write a note on ocular insert.
Intraocular barriers restrict the penetration of drugs into ocular tissues, making eye drug delivery challenging. The main barriers are:
Corneal barrier: The corneal epithelium has tight junctions and acts as a lipophilic barrier, limiting drug permeation.
Blood-aqueous barrier: Formed by the ciliary epithelium and iris vasculature; restricts drug movement from blood to the aqueous humor.
Blood-retinal barrier: Comprises tight junctions in retinal pigment epithelium and retinal vessels, preventing drugs from reaching the posterior eye segment.
Tear turnover and blinking: Wash out drugs rapidly after topical administration, reducing contact time.
To overcome these, ocular inserts are developed. Ocular inserts are sterile, solid or semi-solid preparations placed in the conjunctival sac to provide sustained drug release. They enhance bioavailability, reduce dosing frequency, and ensure better patient compliance.
Examples:
Ocusert: Delivers pilocarpine for glaucoma management.
Lacrisert: A hydroxypropyl cellulose insert for dry eye syndrome.
Advantages:
Sustained and controlled drug release.
Less frequent dosing.
Localized effect with minimal systemic exposure.
Limitations:
Foreign body sensation.
Inconvenient for some patients.
Potential for accidental loss or displacement.
Ocular inserts are an effective alternative to eye drops, especially in chronic ophthalmic conditions requiring prolonged therapy.
17. Discuss metered dose inhalers.
Metered Dose Inhalers (MDIs) are widely used devices in pulmonary drug delivery, especially for treating asthma, COPD, and other respiratory diseases. They consist of a pressurized canister containing the drug in a propellant, an actuator (mouthpiece), and a metering valve to release a pre-measured dose upon activation.
Working:
When the canister is pressed, the propellant forces a specific volume of the drug formulation through the nozzle, producing a fine aerosol that is inhaled directly into the lungs. The formulation may be a solution or suspension, and modern MDIs use hydrofluoroalkane (HFA) propellants instead of CFCs.
Advantages:
Delivers precise doses.
Portable, compact, and easy to carry.
Rapid onset of action.
Suitable for both systemic and local action (e.g., salbutamol for asthma).
Limitations:
Requires hand-breath coordination; improper technique can reduce efficacy.
May lead to oropharyngeal deposition and local side effects (e.g., candidiasis).
Not suitable for delivering large volumes or viscous formulations.
Improvements include use of spacers, which reduce oropharyngeal deposition and improve lung deposition. MDIs are an essential part of naso-pulmonary drug delivery systems, offering convenient and effective treatment options.
18. Discuss floating drug delivery system.
Floating Drug Delivery Systems (FDDS) are a type of gastro-retentive drug delivery system designed to remain buoyant in the stomach for an extended period. These systems enhance drug absorption in the upper gastrointestinal tract by increasing gastric residence time.
Types of FDDS:
Effervescent systems: Contain gas-generating agents like sodium bicarbonate, which react with gastric acid to release CO₂, making the system float.
Non-effervescent systems: Use swellable polymers (e.g., HPMC, ethyl cellulose) that swell and maintain low density.
Advantages:
Prolongs gastric retention of drugs with a narrow absorption window.
Enhances bioavailability of drugs absorbed primarily in the stomach or upper intestine (e.g., ciprofloxacin, amoxicillin).
Reduces fluctuations in plasma drug levels.
Limitations:
Not suitable for drugs that are unstable in acidic pH.
Floating ability can be affected by gastric motility, food, and patient posture.
May not be suitable for drugs with delayed gastric emptying issues.
FDDS are widely used for drugs with low solubility in higher pH, site-specific absorption, or local gastric effects. These systems improve therapeutic efficiency, reduce dosing frequency, and enhance patient compliance.
19. Write a note on liposomes, niosomes and nanoparticles.
Liposomes, niosomes, and nanoparticles are colloidal drug carriers used in modern drug delivery systems for targeted and controlled drug release.
Liposomes:
Spherical vesicles composed of phospholipid bilayers.
Can encapsulate both hydrophilic (in the core) and lipophilic (in bilayers) drugs.
Used for targeted delivery, especially in cancer (e.g., Doxil—liposomal doxorubicin).
Improve bioavailability and reduce toxicity.
Niosomes:
Similar to liposomes but made from non-ionic surfactants instead of phospholipids.
More stable, less costly, and easier to prepare.
Suitable for topical, oral, and parenteral drug delivery.
Nanoparticles:
Solid colloidal particles ranging from 10–1000 nm, made of biodegradable polymers (e.g., PLGA, chitosan).
Can encapsulate drugs within or adsorb on the surface.
Used for controlled release, targeting, and crossing biological barriers (e.g., BBB, ocular barriers).
Applications:
Cancer therapy.
Brain and ocular drug delivery.
Vaccine delivery.
Gene and protein delivery.
These advanced systems offer advantages like improved solubility, targeted delivery, reduced side effects, and enhanced therapeutic performance.
20. Explain the principles of bioadhesion. Give advantages and disadvantages of mucosal drug delivery system.
Bioadhesion refers to the attachment of a drug delivery system to a biological membrane, such as the mucosal surface, via intermolecular interactions (e.g., hydrogen bonds, electrostatic forces, van der Waals forces).
Principles of Bioadhesion:
Contact Stage: The dosage form comes in contact with the mucosal surface and spreads.
Consolidation Stage: Interpenetration of polymer chains and mucin, leading to bond formation.
Factors influencing bioadhesion:
Polymer properties (e.g., molecular weight, flexibility).
Mucosal tissue properties.
pH and hydration level.
Advantages of Mucosal Drug Delivery:
Bypasses first-pass metabolism.
Offers rapid drug absorption and onset.
Suitable for systemic delivery of peptides/proteins.
Provides localized action for oral, nasal, vaginal, or rectal therapy.
Disadvantages:
Limited drug loading capacity.
Mucosal turnover and enzymatic degradation.
Irritation or discomfort at the site.
Drugs may be washed away by saliva or mucous secretions.
Examples include buccal films, nasal gels, and vaginal rings. Mucosal systems are especially useful for drugs with poor oral bioavailability or those requiring fast action.
21. Draw a neat labeled diagram of skin. Discuss the factors affecting skin permeation.
(For exam: draw a clear, labeled diagram showing skin layers: Stratum corneum, Epidermis, Dermis, Subcutaneous tissue, along with structures like hair follicles, sweat glands, and capillaries.)
Skin permeation is the process of drug movement across the skin layers, primarily through the stratum corneum, the outermost layer. It serves as the primary barrier in transdermal delivery.
Factors Affecting Skin Permeation:
Drug Properties:
Lipophilicity: Moderate lipophilicity (LogP ~1–3) enhances permeation.
Molecular weight: Ideal is <500 Da.
Ionization: Non-ionized drugs permeate better.
Formulation Factors:
Use of penetration enhancers (e.g., DMSO, oleic acid).
Vehicle composition (e.g., ethanol increases permeability).
Occlusion increases hydration and absorption.
Skin Condition:
Hydration: Hydrated skin absorbs better.
Age and thickness: Thinner skin in infants or elderly enhances permeation.
Skin diseases: Eczema or wounds may alter absorption.
Application Site:
Varies by body part (e.g., abdomen > forearm).
Understanding these factors helps in designing effective transdermal drug delivery systems (TDDS) that ensure proper drug absorption, controlled release, and improved patient compliance.
Novel Drug Delivery System Long Question Answers [10 Marks]
1. Explain the different formulation approaches of Transdermal Drug Delivery Systems (TDDS).
Transdermal Drug Delivery Systems (TDDS) are designed to deliver drugs through the skin to achieve systemic effects. The major challenge in TDDS is overcoming the stratum corneum, which acts as the primary barrier to drug permeation. Therefore, various formulation approaches are developed to enhance drug delivery through the skin.
Formulation Approaches:
Drug-in-adhesive system:
The drug is directly incorporated into the adhesive layer, which sticks the patch to the skin. These are easy to manufacture and widely used.
Example: Fentanyl patches.
Reservoir system:
A separate drug reservoir is enclosed between a backing layer and a rate-controlling membrane. The membrane regulates the release of the drug.
Example: Nitroglycerin patch.
Matrix system:
The drug is dispersed uniformly in a polymer matrix, which controls its diffusion.
Example: Diclofenac patch.
Micro-reservoir system:
Combines reservoir and matrix system. Drug reservoirs are formed within a polymeric matrix.
Penetration enhancers:
Chemical enhancers like oleic acid, DMSO, surfactants disrupt the stratum corneum to increase drug permeation.
Iontophoresis:
A small electric current is used to drive charged drug molecules through the skin.
Sonophoresis:
Uses ultrasound to enhance skin permeability.
Microneedle systems:
Create micro-channels in the skin through which the drug can diffuse.
Vesicular systems:
Use carriers like liposomes, niosomes, or transfersomes to enhance delivery.
Nanocarrier-based systems:
Use solid lipid nanoparticles, nanostructured lipid carriers, etc., to improve drug stability and penetration.
Conclusion:
These approaches overcome the barrier effect of the skin, enhance bioavailability, and provide controlled drug release. TDDS offers advantages like bypassing first-pass metabolism, sustained release, and improved patient compliance.
2. Discuss Implantable Drug Delivery System and explain in detail Osmotic Pump.
Implantable Drug Delivery Systems (IDDS) are medical devices placed subcutaneously or intramuscularly to release drugs over an extended period. They provide site-specific, controlled, and sustained drug delivery.
Types of Implants:
Non-biodegradable implants (e.g., Norplant): Surgically inserted and removed after drug depletion.
Biodegradable implants (e.g., Gliadel wafer): Degrade after releasing the drug, avoiding the need for removal.
Advantages:
Avoids first-pass metabolism.
Long-term drug delivery.
Reduces dosing frequency.
Improves patient compliance.
Limitations:
Requires minor surgery.
Risk of infection.
Limited to potent drugs due to small size.
Osmotic Pump (e.g., DUROS system)
An osmotic pump is a specialized implant that uses osmotic pressure to deliver drugs in a controlled manner.
Working Principle:
Composed of a semi-permeable membrane, drug reservoir, and osmotic agent.
Water enters the device through the membrane due to osmotic pressure.
Water dissolves the osmotic agent, increasing pressure.
Pressure pushes the drug solution out through a delivery orifice at a constant rate.
Types:
Elementary Osmotic Pump (EOP)
Push-pull Osmotic Pump
DUROS system (used in implants)
Applications:
Hormone delivery (e.g., leuprolide).
Chronic conditions like pain, cancer, and hypertension.
Conclusion:
Implantable systems and osmotic pumps provide precise control over drug delivery, making them ideal for long-term treatments with improved compliance and minimal dosing errors.
Let me know when you're ready for the remaining 10-mark answers:
Controlled release formulations (2 versions)
Combined question on implants + osmotic pumps
TDDS approaches
Development, advantages & disadvantages of IUDs
3. Discuss in detail about Controlled Drug Delivery Systems (CDDS).
Controlled Drug Delivery Systems (CDDS) are dosage forms designed to release drugs at a predetermined rate, for a specific period, to achieve and maintain optimum therapeutic concentration in the systemic circulation.
Objectives of CDDS:
Improve patient compliance by reducing dosing frequency.
Minimize fluctuations in plasma drug levels.
Enhance bioavailability.
Reduce side effects by avoiding peak plasma concentrations.
Types of Controlled Release Systems:
Diffusion-controlled systems:
Reservoir type: Drug core surrounded by rate-controlling membrane (e.g., Transdermal patches).
Matrix type: Drug dispersed in a polymer matrix and released via diffusion.
Dissolution-controlled systems:
Coating-based: Slowly dissolving polymer coats control the release.
Matrix-based: Polymer matrix erodes/dissolves to release the drug.
Osmotic-controlled systems:
Use osmotic pressure to control drug release (e.g., OROS systems).
Bio-responsive systems:
Drug release triggered by physiological conditions (e.g., glucose-responsive insulin systems).
Ion-exchange systems:
Drug is bound to ion-exchange resin and released via ion exchange.
Floating/Gastro-retentive systems:
Remain in the stomach and provide prolonged release for upper GIT absorption.
Ideal Properties of Drugs for CDDS:
Short biological half-life.
Low dose requirement.
Stable in GI environment.
Good absorption throughout GI tract.
Advantages:
Consistent plasma drug levels.
Improved patient adherence.
Reduced frequency of dosing.
Decreased risk of overdose/toxicity.
Disadvantages:
Complex formulation process.
High cost of development.
Dose dumping risk (especially in matrix systems).
Conclusion:
CDDS are critical in modern pharmacotherapy, offering tailored release profiles to improve therapeutic efficacy, reduce side effects, and optimize patient compliance.
4. Explain in detail the approaches of controlled release drug delivery system.
Controlled Release Drug Delivery Systems (CRDDS) maintain consistent drug levels in plasma over an extended period. The approaches can be broadly categorized based on mechanisms of drug release.
Approaches:
Diffusion-Controlled Systems:
Reservoir System: Drug core surrounded by polymer membrane. Drug diffuses slowly (e.g., Nitroglycerin patch).
Matrix System: Drug dispersed in polymer matrix; diffuses as outer layers dissolve.
Dissolution-Controlled Systems:
Drug release controlled by dissolution of polymer or drug.
Useful for water-insoluble drugs (e.g., coated tablets with cellulose derivatives).
Osmotically Controlled Systems:
Use semi-permeable membranes and osmotic pressure (e.g., OROS®).
Provide zero-order release and unaffected by GI pH or motility.
Bioerodible Systems:
Made from biodegradable polymers (e.g., PLGA, PCL).
Polymer degrades slowly, releasing the drug.
Ion-Exchange Resin Systems:
Drug bound to ion-exchange resins; released via ion-exchange in GI fluids.
Responsive Drug Delivery:
Release based on physiological triggers like pH, temperature, enzymes, or glucose levels.
Gastro-retentive Systems:
Floating, mucoadhesive, or expandable systems designed to retain drug in stomach.
Transdermal Controlled Systems:
Patches that allow drug diffusion through skin over extended time.
Advantages:
Better patient adherence.
Reduces side effects and dosing frequency.
Maintains therapeutic levels.
Challenges:
Complexity in formulation.
Risk of failure in critical conditions.
Not suitable for all drugs (e.g., high dose, short half-life).
Conclusion:
Various CRDDS approaches are applied to suit drug characteristics and therapeutic needs, offering precision in drug release and greater therapeutic success.
5. Write in detail about implants and osmotic pump drug delivery systems.
Implants and osmotic pumps are advanced controlled drug delivery systems used for chronic diseases, ensuring long-term, site-specific, and sustained drug release.
A. Implants
Definition:
Solid or semi-solid drug delivery systems placed surgically or via injection into body tissues (e.g., subcutaneous, intramuscular, or ocular).
Types:
Non-biodegradable implants: Made from silicone or EVA (e.g., Norplant); require surgical removal after use.
Biodegradable implants: Made from polymers like PLGA, degrade naturally (e.g., Gliadel wafer for brain tumors).
Advantages:
Long-term therapy (weeks to years).
Bypasses GI and first-pass metabolism.
Local or systemic action.
High patient compliance.
Disadvantages:
Surgical insertion/removal.
Risk of infection or rejection.
Limited to potent drugs.
B. Osmotic Pump Systems
Definition:
Devices that use osmotic pressure to deliver the drug at a controlled rate.
Components:
Core: Drug + osmotic agent.
Semi-permeable membrane: Allows water in, but not solutes.
Delivery orifice: Releases drug solution under pressure.
Mechanism:
Water enters via osmosis → builds pressure → pushes drug out via orifice → constant release.
Types:
Elementary Osmotic Pump (EOP): Simple core with semi-permeable coating.
Push-Pull Pump: Dual-layer core with push compartment.
Implantable Osmotic Systems (DUROS): Used for chronic diseases like cancer, pain management.
Advantages:
Predictable, zero-order drug release.
Unaffected by GI pH, motility, or food.
Long-acting and reliable.
Disadvantages:
Complex design and costly.
Mechanical failure possible.
Conclusion:
Both systems offer sustained and precise drug delivery with high patient compliance and minimal side effects. They are especially valuable in oncology, hormone therapy, and CNS disorders.
6. Describe the development, advantages and disadvantages of IUDs.
Intrauterine Devices (IUDs) are small, T-shaped devices inserted into the uterus for long-term contraception and localized drug delivery. Their development has evolved from mechanical contraceptives to medicated drug delivery systems.
Development:
1st Generation: Non-medicated (e.g., Lippes loop) – caused local inflammation.
2nd Generation: Copper IUDs (e.g., Copper-T) – release copper ions, toxic to sperm.
3rd Generation: Hormonal IUDs (e.g., Mirena) – release levonorgestrel for 3–5 years.
Recent: Biodegradable or programmable IUDs for non-hormonal, localized therapy.
Advantages:
Long-term (3–10 years) and reversible.
Localized effect – minimal systemic side effects.
Avoids hepatic first-pass metabolism.
Improved patient compliance – no daily dosing.
Suitable for contraception, endometriosis, hormone therapy, and potentially uterine cancer treatment.
Disadvantages:
Risk of pelvic inflammatory disease (PID).
Possible expulsion or migration.
May cause pain, bleeding, or discomfort.
Requires trained personnel for insertion/removal.
Not ideal for women with active uterine infections.
Applications Beyond Contraception:
Drug-eluting IUDs for endometrial hyperplasia.
Local delivery of anti-inflammatory drugs.
Experimental delivery of anticancer agents.
Conclusion:
IUDs are versatile devices with therapeutic and contraceptive uses, offering targeted, prolonged, and controlled drug release with minimal systemic exposure. Their continued innovation may expand their utility into broader areas of localized uterine therapies.
7. Explain Liposomes with classification, method of preparation, evaluation and applications.
Liposomes are spherical vesicles composed of one or more phospholipid bilayers that can encapsulate both hydrophilic (in aqueous core) and lipophilic (in bilayer) drugs. They are among the most studied and successful drug carriers in targeted drug delivery systems (TDDS).
Classification of Liposomes:
Based on Structure:
Unilamellar vesicles (ULVs):
Small (SUVs): 20–100 nm.
Large (LUVs): >100 nm.
Multilamellar vesicles (MLVs): Multiple concentric bilayers.
Based on Method of Preparation:
Conventional liposomes.
Stealth liposomes (PEGylated – prolonged circulation).
Immunoliposomes (with monoclonal antibodies for targeting).
Based on Composition:
Neutral, cationic, or anionic liposomes.
Method of Preparation:
Thin Film Hydration Method (Bangham method):
Lipids are dissolved in organic solvents → solvent evaporated to form thin film → hydrated with aqueous phase to form MLVs.
Reverse Phase Evaporation Method:
Water-in-oil emulsion formed and then evaporated under reduced pressure to form liposomes.
Ethanol Injection Method:
Lipid in ethanol injected into aqueous phase, forming SUVs.
Sonication/Extrusion:
Reduces particle size and forms unilamellar vesicles.
Evaluation of Liposomes:
Vesicle size and distribution: Dynamic light scattering (DLS), electron microscopy.
Encapsulation efficiency: Centrifugation or dialysis followed by drug estimation.
Zeta potential: Indicates surface charge and stability.
In vitro drug release: Dialysis or diffusion studies.
Stability studies: Temperature, pH, and time-dependent changes.
Applications:
Cancer chemotherapy: Doxil® (liposomal doxorubicin).
Antifungal: Amphotericin B liposomes.
Vaccines: Liposomal adjuvants (e.g., mRNA COVID vaccines).
Gene delivery: Lipoplexes for DNA/RNA transport.
Dermatology: Topical drug delivery (anti-acne, antifungals).
Conclusion:
Liposomes are versatile and biocompatible carriers that offer controlled release, reduced toxicity, and site-specific targeting. With continued advancements, liposomes remain a cornerstone in novel drug delivery systems.
8. Classify and explain Buccal Drug Delivery Systems with its formulation considerations.
Buccal Drug Delivery System (BDDS) refers to the delivery of drugs through the buccal mucosa (cheek) for either local or systemic effects. It bypasses hepatic first-pass metabolism and provides rapid drug absorption due to rich vascularization.
Classification of Buccal DDS:
Based on Retention:
Adhesive systems: Remain attached to mucosa (e.g., buccal films, patches).
Non-adhesive systems: Lozenge, mouthwashes (transient contact).
Based on Dosage Form:
Solid: Tablets, patches, lozenges, wafers.
Semi-solid: Gels, ointments.
Liquid: Mouth sprays, rinses.
Based on Direction of Release:
Unidirectional: Drug release only toward mucosa (backing layer).
Bidirectional: Drug diffuses in both directions.
Formulation Considerations:
Drug Properties:
Molecular weight <500 Da, lipophilic, stable in saliva, and potent at low doses.
Preferably non-irritating to the mucosa.
Mucoadhesive Polymers:
Natural: Chitosan, pectin.
Synthetic: Carbopol, HPMC, polycarbophil.
Help in prolonged retention and enhanced absorption.
Permeation Enhancers:
Surfactants (SLS), bile salts, fatty acids, or enzyme inhibitors.
Enhance drug transport by opening tight junctions or modifying lipid structure.
Backing Layer:
Impermeable to prevent drug loss to saliva (e.g., ethyl cellulose, aluminium foil).
pH Modifiers:
Maintain local pH (5.5–7) to optimize drug solubility and permeability.
Enzyme Inhibitors:
Prevent enzymatic degradation of proteins/peptides.
Advantages:
Avoids GI degradation and hepatic metabolism.
Rapid onset of action.
Suitable for drugs unstable in GIT.
Ease of administration and removal.
Limitations:
Salivary wash-out.
Low permeability for some drugs.
Small surface area compared to GIT.
Taste masking may be required.
Conclusion:
Buccal DDS offers a safe, effective, and non-invasive alternative for drugs requiring rapid absorption and controlled release, especially for emergency, hormonal, and protein-based therapies.
9. What are Niosomes? Describe their advantages, preparation methods and applications.
Niosomes are non-ionic surfactant-based vesicles used as carriers for novel drug delivery systems. Structurally, they resemble liposomes but are made from non-ionic surfactants and cholesterol. They are biodegradable, biocompatible, and non-immunogenic.
Advantages of Niosomes:
Stable compared to liposomes.
Cost-effective due to synthetic surfactants.
Capable of encapsulating both hydrophilic and lipophilic drugs.
Controlled and targeted drug release.
Enhanced drug bioavailability and reduced toxicity.
Suitable for oral, parenteral, ocular, transdermal, and pulmonary routes.
Methods of Preparation:
Thin Film Hydration Method:
Surfactants and cholesterol dissolved in organic solvent.
Evaporated to form thin film → hydrated with aqueous drug solution → MLVs formed.
Reverse Phase Evaporation:
Water-in-oil emulsion prepared → solvent removed → vesicle formation.
Microfluidization:
High shear method producing uniform-sized small vesicles.
Sonication:
Disrupts MLVs into SUVs using ultrasonic waves.
Ether Injection Method:
Solution of surfactant injected into hot aqueous phase → forms vesicles upon solvent evaporation.
Evaluation Parameters:
Particle size: Dynamic Light Scattering (DLS).
Entrapment efficiency: Dialysis or centrifugation method.
In-vitro release studies: Diffusion techniques.
Stability testing: pH, temperature, aggregation.
Applications of Niosomes:
Targeted drug delivery:
Anti-cancer (e.g., methotrexate, doxorubicin).
Antimicrobials (e.g., amphotericin B, rifampicin).
Transdermal drug delivery:
Improves permeation of drugs across skin (e.g., diclofenac, ibuprofen).
Ocular delivery:
Enhances retention time and penetration (e.g., timolol).
Vaccine delivery:
Acts as adjuvant and delivery vehicle for antigens.
Cosmetics:
Used in anti-aging and moisturizing products.
Conclusion:
Niosomes are a promising alternative to liposomes, offering targeted, controlled, and versatile delivery options. Their cost-effectiveness and stability make them suitable for both pharmaceutical and cosmetic industries.
B.Pharmacy 7th Semester Novel Drug Delivery System Important Question Answer
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