Modified Release Oral Dosage Forms I

Vocabulary practice flashcards covering modified release classifications, kinetics, matrix systems, polymers, excipients, and gastroretentive technologies.

Modified Release Dosage Form

A drug delivery formulation designed to alter the timing, rate, or site of drug release relative to conventional immediate-release dosage forms to prolong absorption, sustain therapeutic levels, or reduce dosing frequency.

Sustained Release (SR)

Any oral drug delivery system that achieves a slow, extended release of drug over a prolonged period of time, synonymous with prolonged release or extended release.

Controlled Release (CR)

A specific class of modified release delivery system in which drug release is governed at a constant rate, typically following zero-order release kinetics ($\text{rate} = k_0$) in a planned and intentional pattern.

Delayed Release

A formulation that defers the onset of drug release until a predetermined time has elapsed or specific physiological conditions are met, such as transit past the stomach.

Pulsatile Release

A drug release profile characterized by transient bursts or sequential pulses of rapid drug release separated by predefined lag phases of minimal or no release.

Dose Dumping

The sudden, unintended, and complete release of the entire loaded dose of drug from a modified release system into the gastrointestinal tract, presenting a severe risk of drug toxicity.

Homogeneous Matrix System

An extended-release formulation in which the drug substance is dissolved or uniformly dispersed throughout a polymer matrix and released primarily by diffusion through the polymer phase.

Inert Matrix System

An extended-release system containing an insoluble, non-swelling, non-eroding matrix; gastrointestinal fluids enter through open pores to dissolve the drug, which then diffuses out through the resulting water-filled tortuous channels.

Hydrophilic (Eroding) Matrix System

An extended-release tablet in which drug is dispersed in a water-swellable polymer that hydrates upon contact with aqueous fluid to form a protective gel layer, releasing drug by both diffusion through the gel and outer polymer chain erosion.

Depletion Zone

The advancing, drug-depleted outer region of a matrix tablet that forms as drug dissolves and leaves the matrix, requiring remaining drug from the inner core to diffuse a greater distance to reach the surface.

Square-Root of Time Dependency

A mathematical relationship governing diffusion-controlled drug release from planar matrix systems, where the cumulative drug amount released ($Q$) is directly proportional to $t^{1/2}$.

Ghost Matrix

An insoluble, non-absorbable tablet skeleton (such as an inert wax matrix) that remains intact after all drug has eluted and is eliminated visible and unchanged in the stool.

Hypromellose (HPMC)

A widely utilized hydrophilic, semi-synthetic cellulose ether polymer that hydrates and swells in water to generate a rate-controlling gel layer in hydrophilic matrix tablets.

Enteric Coating

A specialized polymer barrier applied to oral dosage forms that remains insoluble in acidic gastric fluid ($\text{pH } 1.2\text{ to } 2$) but dissolves in higher pH environments ($\text{pH } 6\text{ to } 7.4$) of the small intestine.

Geomatrix System

A multi-layer tablet technology consisting of a drug-containing hydrophilic core bounded on one or more faces by swellable or erodible barrier layers to prevent reductions in surface area and maintain near zero-order release.

Gastroretentive Drug Delivery System

A dosage form designed to prolong gastric residence time in the stomach, facilitating continuous local delivery or sustained absorption for drugs possessing a narrow absorption window in the upper gastrointestinal tract.

Floating Drug Delivery System

A low-density gastroretentive formulation utilizing effervescent gas-generating agents or low-density polymers to maintain buoyancy on gastric fluids above the pylorus.

Swelling Gastroretentive System

A gastroretentive tablet containing expandable polymers that imbibes gastric fluid and expands significantly (e.g., expanding to $150\%$ its original size) so that its dimensions exceed the diameter of the resting pyloric sphincter.

Mucoadhesive Gastroretentive System

A gastroretentive platform containing bioadhesive polymers that adhere directly to the gastric mucin layer lining the stomach wall, resisting natural peristaltic clearance.

Raft-Forming System

A gastroretentive formulation that forms a cohesive, floating viscous gel barrier or raft upon contact with gastric fluids, commonly used to prevent gastroesophageal reflux or prolong gastric retention.

Dual Hydrophilic Polymer Matrix System

A formulation architecture (such as Glucophage XR) wherein drug is intimately associated with a release-controlling polymer to form an internal particulate phase embedded inside an outer continuous phase of a second hydrophilic polymer.

Carrier-Mediated Transport Limitation

A physiological barrier to modified release therapy occurring when a drug depends on specialized, saturable intestinal transporters located only in specific regions of the gastrointestinal tract.