Introduction: Implantable drug delivery systems are advanced therapeutic devices designed to deliver drugs at controlled rates directly at the target site for prolonged periods. Key concepts include controlled release, biodegradable implants, polymeric implants, osmotic pumps, and reservoir versus matrix systems. Important considerations for B.Pharm students are biocompatibility, release kinetics (diffusion, erosion, osmotic), material selection (PLGA, EVA, silicone), sterilization, and safety monitoring. Understanding these systems helps optimize pharmacokinetics, reduce dosing frequency, and improve patient compliance. This overview emphasizes mechanism, design, and regulatory aspects to prepare you for applied questions and clinical examples. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary advantage of implantable drug delivery systems over conventional oral dosage forms?
- Higher manufacturing cost
- Reduced need for repeated dosing
- Greater systemic side effects
- Lower patient compliance
Correct Answer: Reduced need for repeated dosing
Q2. Which mechanism commonly produces near zero-order release from an implant?
- Simple diffusion through a porous matrix
- Surface erosion of a biodegradable polymer
- Osmotic pumping with a constant driving force
- Immediate burst release from a reservoir
Correct Answer: Osmotic pumping with a constant driving force
Q3. Which polymer is most commonly used for biodegradable implants in controlled release applications?
- Polyethylene (PE)
- Polylactic-co-glycolic acid (PLGA)
- Polytetrafluoroethylene (PTFE)
- Polyvinyl chloride (PVC)
Correct Answer: Polylactic-co-glycolic acid (PLGA)
Q4. A matrix-type implant releases drug primarily by which process?
- Active pumping
- Diffusion through the swollen matrix
- Evaporation of solvent
- Ion-exchange heating
Correct Answer: Diffusion through the swollen matrix
Q5. Which of the following is a non-biodegradable implant material often used in long-term implants?
- PLGA
- Polyethylene glycol (PEG)
- Silicone elastomer
- Gelatin
Correct Answer: Silicone elastomer
Q6. What is a major clinical concern with implantable drug delivery systems?
- Instant oral absorption
- Foreign body reaction and fibrosis
- Excessive gastric irritation
- Uncontrolled renal excretion
Correct Answer: Foreign body reaction and fibrosis
Q7. Which implant example is an FDA-approved subdermal contraceptive implant?
- Insulin pump
- Norplant/Implanon (etonogestrel)
- Gliadel wafer
- Pacemaker
Correct Answer: Norplant/Implanon (etonogestrel)
Q8. In reservoir (membrane-controlled) implants, drug release is primarily controlled by:
- Degradation of the core drug
- Permeability of the rate-limiting membrane
- Drug ionic strength
- External temperature alone
Correct Answer: Permeability of the rate-limiting membrane
Q9. Which sterilization method is commonly used for polymeric implants but may cause polymer degradation at high doses?
- Autoclaving at 121°C
- Gamma irradiation
- Filtration through 0.22 µm
- Ultrasonic cleaning
Correct Answer: Gamma irradiation
Q10. Gliadel wafers used for brain tumor local chemotherapy are an example of which implant type?
- Biodegradable polymer matrix implant
- Non-biodegradable osmotic pump implant
- Transdermal patch
- Oral sustained-release tablet
Correct Answer: Biodegradable polymer matrix implant
Q11. Which factor does NOT significantly influence drug release from an implant?
- Drug molecular weight
- Polymer crystallinity
- Ambient light intensity
- Implant geometry and surface area
Correct Answer: Ambient light intensity
Q12. What does the term “first pass metabolism” refer to, and how do implants circumvent it?
- Renal filtration before absorption; implants increase filtration
- Hepatic metabolism after oral absorption; implants deliver drug directly to systemic or local site, reducing hepatic first-pass
- Pulmonary metabolism during inhalation; implants enhance lung uptake
- Skin metabolism during topical use; implants slow skin enzymes
Correct Answer: Hepatic metabolism after oral absorption; implants deliver drug directly to systemic or local site, reducing hepatic first-pass
Q13. Which release profile is most desirable for chronic disease management using implants?
- Sharp peak followed by rapid decline
- Zero-order or near zero-order steady release
- Complete immediate release
- Highly erratic pulsatile release
Correct Answer: Zero-order or near zero-order steady release
Q14. Which analytical test is essential for in vitro evaluation of implant release kinetics?
- In vitro dissolution testing under sink conditions
- Gram staining
- Blood glucose measurement
- Urine dipstick
Correct Answer: In vitro dissolution testing under sink conditions
Q15. Refillable implantable systems are designed to allow:
- Immediate biodegradation after insertion
- Refilling of the drug reservoir without full removal
- Replacement of polymer matrix with tablets
- Oral administration of the same drug
Correct Answer: Refilling of the drug reservoir without full removal
Q16. Which mechanism describes polymer degradation where the surface erodes but the core remains intact?
- Bulk erosion
- Surface erosion
- Osmotic swelling
- Diffusion-limited erosion
Correct Answer: Surface erosion
Q17. For a hydrophilic drug in a hydrophobic polymer matrix, initial release is often characterized by:
- High burst release due to drug solubility mismatch
- No release ever
- Only enzymatic activation
- Immediate polymer melting
Correct Answer: High burst release due to drug solubility mismatch
Q18. Which regulatory category often applies to implantable drug delivery devices that combine device and drug?
- Food additive
- Combination product (drug-device)
- Dietary supplement
- Cosmetic
Correct Answer: Combination product (drug-device)
Q19. What role does glass transition temperature (Tg) of a polymer play in implant performance?
- It determines polymer melting in the stomach
- It affects polymer mobility and drug diffusion at body temperature
- It controls electrical conductivity
- It is irrelevant for in vivo applications
Correct Answer: It affects polymer mobility and drug diffusion at body temperature
Q20. Which imaging technique is commonly used to monitor implant position and integrity in vivo?
- Gas chromatography
- Magnetic resonance imaging (MRI) or X-ray when appropriate
- UV-visible spectrophotometry
- Thin layer chromatography
Correct Answer: Magnetic resonance imaging (MRI) or X-ray when appropriate
Q21. Which property of a drug favors sustained release from an implant?
- Very high aqueous solubility and low potency
- Low potency and rapid clearance
- High potency and moderate lipophilicity
- Extreme instability in physiological conditions
Correct Answer: High potency and moderate lipophilicity
Q22. What is the main advantage of biodegradable implants compared to non-biodegradable ones?
- They always provide zero-order release
- No need for surgical removal after drug depletion
- They are indestructible
- They are unaffected by polymer degradation products
Correct Answer: No need for surgical removal after drug depletion
Q23. Which in vivo concern is especially important for intracranial implants like wafers?
- Gastrointestinal upset
- Local neurotoxicity and inflammation
- Ear infection
- Tooth decay
Correct Answer: Local neurotoxicity and inflammation
Q24. Which factor is critical when selecting a polymer for an implantable device?
- Compatibility with the drug and predictable degradation or stability
- Color matching with skin tone
- Ability to dissolve instantly in water
- High electrical resistance only
Correct Answer: Compatibility with the drug and predictable degradation or stability
Q25. Which term describes the unwanted high initial drug release from an implant?
- Lag phase
- Burst release
- Sustained plateau
- Zero-order elution
Correct Answer: Burst release
Q26. Which type of implant uses a semipermeable membrane and an osmotic agent to push drug out through a small orifice?
- Matrix erosion implant
- Reservoir diffusion implant
- Osmotic pump implant (implantable Oros-like device)
- Transdermal patch
Correct Answer: Osmotic pump implant (implantable Oros-like device)
Q27. Biocompatibility testing for implants commonly evaluates which of the following?
- Color change in daylight
- Cytotoxicity, sensitization, and implantation-induced inflammation
- Solubility in ethanol only
- Ability to be sterilized by boiling
Correct Answer: Cytotoxicity, sensitization, and implantation-induced inflammation
Q28. Which clinical example demonstrates a local implant used in the eye to deliver steroids?
- Insulin implant
- Ozurdex (dexamethasone intravitreal implant)
- Norplant contraceptive
- Gliadel wafer
Correct Answer: Ozurdex (dexamethasone intravitreal implant)
Q29. Which release mechanism depends on polymer swelling followed by drug diffusion through the swollen network?
- Surface erosion
- Swelling-controlled release (Hydrophilic matrix)
- Immediate bolus release
- Electrochemical cleavage
Correct Answer: Swelling-controlled release (Hydrophilic matrix)
Q30. When designing an implant for chronic delivery, which pharmacokinetic parameter is most improved by steady implant release?
- Peak-to-trough fluctuation and maintenance of therapeutic levels
- Rapid peak concentration for immediate effect
- Increased first-pass hepatic metabolism
- Immediate renal clearance
Correct Answer: Peak-to-trough fluctuation and maintenance of therapeutic levels
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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