Rate controlled drug delivery: principles MCQs With Answer

Rate controlled drug delivery: principles MCQs With Answer offers a focused self-assessment resource for M.Pharm students studying Drug Delivery Systems (MPH 102T). This quiz set covers foundational and advanced principles that govern rate-controlled systems, including zero-order kinetics, diffusion and dissolution control, osmotic mechanisms, membrane variables, polymer erosion, and in vitro–in vivo considerations. You will explore model equations (Fick, Higuchi, Korsmeyer–Peppas), design trade-offs (matrix vs reservoir), transdermal and oral systems, and criteria for drug and polymer selection. Each question is designed to strengthen conceptual clarity while linking theory to device performance and pharmacokinetics. Use these MCQs to refine exam readiness and deepen practical understanding of controlled release design.

Q1. The primary principle behind rate-controlled drug delivery is to:

• maximize fluctuation between Cmax and Cmin
• synchronize drug input with the body’s circadian rhythm only
• match drug input rate to drug elimination rate to maintain concentrations within therapeutic window
• ensure drug accumulates to toxic levels for efficacy

Correct Answer: match drug input rate to drug elimination rate to maintain concentrations within therapeutic window

Q2. Zero-order drug release from a delivery system is best defined as:

• release rate proportional to the square root of time
• release rate proportional to the amount of drug remaining
• constant release rate independent of the amount remaining
• rapid initial burst followed by exponential decline

Correct Answer: constant release rate independent of the amount remaining

Q3. Which oral system most reliably provides near zero-order release largely independent of GI variables?

• hydrophilic matrix tablet releasing by diffusion
• elementary osmotic pump tablet with semi-permeable membrane and laser-drilled orifice
• simple coated tablet with enteric film
• ion-exchange resin without coating

Correct Answer: elementary osmotic pump tablet with semi-permeable membrane and laser-drilled orifice

Q4. Which statement represents Fick’s first law of diffusion as applied to steady-state membrane transport?

• J = −D (dC/dx), describing steady-state diffusion
• J = D (dC/dt), describing time-dependent diffusion
• J = k0, independent of concentration and distance
• J = −D (dC/dt), describing transient diffusion through time

Correct Answer: J = −D (dC/dx), describing steady-state diffusion

Q5. A key characteristic of the Higuchi model for planar matrices is that it predicts:

• cumulative amount released is proportional to t1/2 from a planar matrix with excess drug loading
• release is proportional to t for all geometries
• diffusion coefficient increases exponentially with time
• assumes drug concentration much lower than its solubility

Correct Answer: cumulative amount released is proportional to t1/2 from a planar matrix with excess drug loading

Q6. In the Korsmeyer–Peppas model for a thin film (slab), an exponent n = 0.5 indicates:

• Case II transport (zero-order, polymer relaxation controlled)
• Fickian diffusion-controlled release
• Super Case II transport
• pure erosion-controlled release

Correct Answer: Fickian diffusion-controlled release

Q7. Which statement about reservoir versus matrix controlled-release systems is most accurate?

• reservoir systems are less susceptible to dose dumping upon membrane failure than matrices
• matrix systems cannot provide sustained release
• reservoir systems can achieve more constant release but risk dose dumping if the membrane ruptures
• matrix systems always yield zero-order kinetics

Correct Answer: reservoir systems can achieve more constant release but risk dose dumping if the membrane ruptures

Q8. For a membrane-controlled reservoir device, which change increases the drug release rate?

• increase membrane thickness while keeping area constant
• decrease membrane permeability
• decrease membrane thickness while keeping area and permeability constant
• reduce drug activity in the core

Correct Answer: decrease membrane thickness while keeping area and permeability constant

Q9. A distinguishing property of osmotic pump systems is that their release rate is:

• increased markedly by external agitation and GI motility
• largely independent of external pH and agitation within physiological range
• ceased when environmental pH is neutral
• dependent on enzymatic degradation of the membrane

Correct Answer: largely independent of external pH and agitation within physiological range

Q10. In ion-exchange resin–based rate-controlled formulations, the dominant determinants of drug release are:

• drug vapor pressure
• counter-ion concentration in the medium and resin crosslinking
• UV light exposure
• gastric emptying time only

Correct Answer: counter-ion concentration in the medium and resin crosslinking

Q11. A transdermal therapeutic system achieves near constant input primarily by:

• keeping patch drug concentration low to avoid constant gradient
• ensuring drug activity in the patch remains constant so the skin becomes the rate-controlling barrier
• designing the patch so the adhesive is the rate-limiting layer with zero permeability
• using hydrophilic drugs without enhancers as they permeate stratum corneum readily

Correct Answer: ensuring drug activity in the patch remains constant so the skin becomes the rate-controlling barrier

Q12. Surface-eroding polymers such as polyanhydrides are useful in rate control because they:

• swell extensively before erosion
• can approximate zero-order release when surface area remains constant during erosion
• release is dominated by Fickian diffusion through a swollen matrix
• require high permeation enhancers to function

Correct Answer: can approximate zero-order release when surface area remains constant during erosion

Q13. For a constant-rate input R0 from a rate-controlled device into a linear one-compartment system at steady state:

• R0 = CL × Css
• R0 = Vd × Css
• R0 = k × Css2
• R0 = 0 because input is balanced by output

Correct Answer: R0 = CL × Css

Q14. During in vitro testing of an osmotic pump tablet under sink conditions, which parameter least affects the release rate?

• agitation speed in USP Apparatus 2
• osmotic gradient across the membrane
• membrane thickness
• orifice size (within functional limits)

Correct Answer: agitation speed in USP Apparatus 2

Q15. The initial lag time before steady release from a diffusion membrane–controlled reservoir is primarily governed by:

• membrane thickness and diffusivity of drug within the membrane
• stirring rate of the release medium
• tablet hardness
• color of the coating

Correct Answer: membrane thickness and diffusivity of drug within the membrane

Q16. Which drug property is most favorable for a rate-controlled oral controlled-release system?

• very long elimination half-life (>24 h)
• required daily dose >1 g
• short-to-moderate half-life (2–6 h) and good potency
• extremely low solubility and permeability (BCS Class IV) without enabling approaches

Correct Answer: short-to-moderate half-life (2–6 h) and good potency

Q17. Which is an example of a feedback-regulated drug delivery concept?

• enteric coating dissolving at pH > 5.5
• glucose-responsive hydrogel releasing insulin via glucose oxidase–mediated swelling
• time-dependent rupturable coat releasing drug after a lag time
• heat-sealed reservoir patch

Correct Answer: glucose-responsive hydrogel releasing insulin via glucose oxidase–mediated swelling

Q18. Which strategy best minimizes initial burst release from a diffusion-controlled matrix?

• increase surface drug loading
• use a sealing or barrier coat to reduce surface drug availability
• grind the matrix to increase surface area
• increase porosity at the surface

Correct Answer: use a sealing or barrier coat to reduce surface drug availability

Q19. Which statement correctly distinguishes controlled release from sustained release?

• sustained release strictly means zero-order release
• controlled release implies predictable, often constant or programmable rate; sustained just prolongs release without necessarily being constant
• both terms are interchangeable
• controlled release always uses biodegradable polymers

Correct Answer: controlled release implies predictable, often constant or programmable rate; sustained just prolongs release without necessarily being constant

Q20. Which failure mode most likely leads to dose dumping in reservoir/osmotic systems?

• membrane rupture or oversized orifice greatly increasing flow
• slight variation in excipient color
• use of sink conditions in dissolution media
• addition of buffering agents to the formulation

Correct Answer: membrane rupture or oversized orifice greatly increasing flow

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