Introduction: Controlled drug delivery is a specialized area in pharmaceutics that focuses on designing systems to release therapeutic agents at predetermined rates, for specific durations, and at targeted sites. Key objectives include maintaining plasma drug concentration within the therapeutic window, reducing dosing frequency, minimizing side effects, improving bioavailability, and enhancing patient compliance. Important concepts for B. Pharm students include sustained release, controlled release, targeted delivery, release kinetics (zero-order, first-order, Higuchi), rate-controlling polymers, biodegradation, and reservoir versus matrix systems. Understanding mechanisms (diffusion, erosion, swelling, osmosis) and formulation strategies is essential for rational design of modern controlled delivery systems. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary definition of a controlled drug delivery system?
- A system that delivers a drug at an uncontrolled, variable rate
- A system that releases a drug at a predetermined rate, duration, and/or location
- A system that always provides immediate release of the entire dose
- A system that only masks the taste of drugs
Correct Answer: A system that releases a drug at a predetermined rate, duration, and/or location
Q2. Which of the following is a primary objective of controlled drug delivery?
- Increase dosing frequency
- Maintain plasma concentration within therapeutic window
- Maximize peak-trough fluctuations
- Eliminate pharmacokinetics
Correct Answer: Maintain plasma concentration within therapeutic window
Q3. Which release profile is ideal for many controlled delivery systems to provide constant plasma levels?
- First-order release
- Zero-order release
- Immediate release
- Biphasic burst release
Correct Answer: Zero-order release
Q4. The Higuchi model primarily describes drug release controlled by which mechanism?
- Polymer degradation
- Diffusion from a homogeneous matrix
- Enzymatic cleavage
- Osmosis through a semi-permeable membrane
Correct Answer: Diffusion from a homogeneous matrix
Q5. Which of the following is an example of a reservoir-type controlled release system?
- Drug uniformly dispersed in polymer matrix (monolithic)
- Coated core tablet with rate-controlling membrane
- Immediate-release effervescent tablet
- Simple aqueous solution
Correct Answer: Coated core tablet with rate-controlling membrane
Q6. In a matrix-controlled system, drug release is often governed by:
- Drug molecular weight only
- Diffusion and/or polymer erosion from the matrix
- Only pH changes in blood
- Electrical stimulation exclusively
Correct Answer: Diffusion and/or polymer erosion from the matrix
Q7. Which polymer property is most important for controlling drug release in biodegradable implants?
- Color of the polymer
- Rate of polymer degradation (biodegradation)
- Electrical conductivity
- Melting point only
Correct Answer: Rate of polymer degradation (biodegradation)
Q8. Which mechanism describes release where solvent penetrates, polymer swells, and drug diffuses out?
- Osmotic pumping
- Swelling-controlled release
- Immediate dissolution
- Photochemical cleavage
Correct Answer: Swelling-controlled release
Q9. Osmotic drug delivery systems (e.g., OROS) primarily rely on which principle?
- Enzymatic degradation of polymer
- Pressure generated by osmotic influx through a semi-permeable membrane
- Passive diffusion through the skin
- Magnetic targeting
Correct Answer: Pressure generated by osmotic influx through a semi-permeable membrane
Q10. Which kinetic model corresponds to a release rate proportional to the remaining drug amount?
- Zero-order kinetic model
- First-order kinetic model
- Higuchi model
- Korsmeyer-Peppas model exclusively
Correct Answer: First-order kinetic model
Q11. A major advantage of targeted controlled delivery is:
- Increasing systemic side effects
- Reducing drug concentration at the target site
- Enhancing drug concentration at specific diseased tissues while minimizing systemic exposure
- Shortening drug half-life intentionally
Correct Answer: Enhancing drug concentration at specific diseased tissues while minimizing systemic exposure
Q12. Burst release in controlled systems refers to:
- Initial rapid release of a large fraction of drug
- Complete absence of drug release
- Linear zero-order release throughout
- Release controlled only by enzymatic action
Correct Answer: Initial rapid release of a large fraction of drug
Q13. Which analytical model is often used to characterize anomalous (non-Fickian) transport?
- Higuchi only
- Korsmeyer-Peppas model
- Van’t Hoff equation
- Ideal gas law
Correct Answer: Korsmeyer-Peppas model
Q14. Which of the following is considered a rate-controlling polymer for sustained release oral tablets?
- Hydroxypropyl methylcellulose (HPMC)
- Table salt
- Glucose
- Magnesium stearate only as lubricant
Correct Answer: Hydroxypropyl methylcellulose (HPMC)
Q15. The primary aim of a transdermal controlled delivery system is to:
- Provide erratic peaks and troughs in plasma levels
- Deliver drug across skin to achieve systemic therapeutic levels over extended time
- Cause localized skin irritation intentionally
- Prevent systemic absorption completely
Correct Answer: Deliver drug across skin to achieve systemic therapeutic levels over extended time
Q16. Which formulation type is commonly used for long-acting injectable controlled delivery?
- Sugar-coated immediate-release tablets
- Biodegradable microspheres or polymeric depots
- Simple aqueous bolus injection of free drug
- Effervescent granules
Correct Answer: Biodegradable microspheres or polymeric depots
Q17. Controlled release that aims to reduce dosing frequency primarily improves:
- Patient compliance and adherence
- The need for more frequent hospital visits
- Toxicity intentionally
- Immediate drug clearance
Correct Answer: Patient compliance and adherence
Q18. Which factor does NOT significantly affect diffusion-controlled drug release from a matrix?
- Drug solubility in the matrix
- Diffusion coefficient of the drug in polymer
- Color of the packaging
- Matrix porosity
Correct Answer: Color of the packaging
Q19. Liposomes as controlled delivery carriers are best described as:
- Solid metallic nanoparticles only
- Phospholipid vesicles capable of encapsulating hydrophilic and lipophilic drugs
- Simple sugar crystals
- Non-biocompatible ceramic beads
Correct Answer: Phospholipid vesicles capable of encapsulating hydrophilic and lipophilic drugs
Q20. Which is a disadvantage commonly associated with controlled release formulations?
- Reduced fluctuation in plasma levels
- Potential for dose dumping if system fails
- Improved patient compliance
- Prolonged therapeutic effect
Correct Answer: Potential for dose dumping if system fails
Q21. Site-specific delivery to the colon is often achieved using:
- Enteric coatings and pH-dependent polymers
- Immediate release sugar coatings
- Sublingual fast-dissolving films
- Topical creams only
Correct Answer: Enteric coatings and pH-dependent polymers
Q22. In the Korsmeyer-Peppas model, the release exponent ‘n’ helps to identify:
- The drug’s crystalline form
- The mechanism of drug release (Fickian, non-Fickian, or case-II transport)
- The tablet hardness exclusively
- The assay method for drug content
Correct Answer: The mechanism of drug release (Fickian, non-Fickian, or case-II transport)
Q23. Controlled delivery systems aim to widen the therapeutic index by:
- Increasing peak concentrations to toxic levels
- Maintaining drug concentrations within the therapeutic window and minimizing peaks
- Abolishing all pharmacodynamic effects
- Reducing absorption to zero
Correct Answer: Maintaining drug concentrations within the therapeutic window and minimizing peaks
Q24. Which of the following is a common in vitro method to evaluate controlled release from matrices?
- Dissolution testing using paddle or basket apparatus
- Particle size analysis by microscopy only
- Colorimetric packaging inspection
- Measuring tablet weight only
Correct Answer: Dissolution testing using paddle or basket apparatus
Q25. A self-regulated or feedback-controlled drug delivery system is characterized by:
- Constant release irrespective of physiological condition
- Release modulated in response to biological signals (e.g., glucose levels)
- Only manual activation by the patient
- Release controlled solely by temperature during manufacturing
Correct Answer: Release modulated in response to biological signals (e.g., glucose levels)
Q26. Microspheres used for controlled delivery are typically prepared from:
- Biodegradable polymers such as PLGA
- Pure table sugar
- Metallic alloys
- Unformulated aqueous solutions
Correct Answer: Biodegradable polymers such as PLGA
Q27. Which release mechanism predominates when a polymer matrix erodes steadily and releases drug as fragments detach?
- Diffusion-controlled release exclusively
- Erosion-controlled release
- Osmotic pumping only
- Thermal decomposition
Correct Answer: Erosion-controlled release
Q28. Which parameter is crucial for achieving zero-order release from a reservoir device?
- Constant surface area and controlled diffusion resistance of the rate-controlling membrane
- Rapid disintegration of the membrane
- Variable pore formation randomly
- Immediate burst release of drug
Correct Answer: Constant surface area and controlled diffusion resistance of the rate-controlling membrane
Q29. Targeted nanoparticle delivery to tumors often exploits which property of tumor vasculature?
- Highly ordered tight endothelial junctions
- Enhanced permeability and retention (EPR) effect
- Complete lack of blood vessels
- Lower interstitial fluid pressure relative to normal tissue
Correct Answer: Enhanced permeability and retention (EPR) effect
Q30. For oral controlled release tablets, which criterion is essential during formulation design?
- Drug must have very high dose (>2 g) to be feasible
- Drug should have suitable half-life and therapeutic window for sustained delivery
- Drug must be unstable in stomach and intestine
- Drug should be completely insoluble in GI fluids
Correct Answer: Drug should have suitable half-life and therapeutic window for sustained delivery
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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