ASE201 Drug Delivery Systems Test 2 Review

Vocabulary practice flashcards covering Modified Release, Parenteral, Rectal, Transdermal, Freeze Drying, Nasal, Pulmonary, Ocular, and Vaginal Drug Delivery Systems.

Modified Release (MR)

Dosage forms designed to alter the timing, rate, or location of drug release compared to conventional immediate-release formulations.

Delayed Release

A system where the drug is not released immediately after administration, such as enteric-coated drugs that dissolve only in the higher pH of the small intestine.

Repeat Action systems

A single unit containing more than one immediate-release dose; the first is released shortly after administration, followed by subsequent doses at defined intervals.

Prolonged Release

Dosage forms designed to release drugs slowly and continuously to maintain plasma concentrations within a therapeutic range for $8-12$ hours.

Controlled Release (CR)

A precise iteration of extended release characterized by a constant (zero-order) rate of drug release, resulting in unchanged plasma concentrations over time.

Sustained Release

Formulations that combine an initial immediate-release component with a subsequent extended-release phase for rapid onset and maintained drug levels.

Extended Release (ER)

A broad umbrella term for any formulation that extends the period of drug absorption beyond that of a conventional dosage form.

Breakthrough

A phenomenon where drug concentration falls below the Minimum Effective Concentration (MEC) because a patient is late for a dose or the release is insufficient.

Dose Dumping

A failure in the release-controlling mechanism where a high concentration of the drug (intended for many hours) is suddenly released, risking toxicity.

Biopharmaceutical Classification System (BCS)

A tool classifying drugs based on solubility and permeability; Class I (high solubility/high permeability) is highly suitable for modified release.

Osmotic pump systems

Advanced systems using a rigid membrane with a laser-drilled hole; water entering via osmosis expands a salt layer to force the drug out at a zero-order rate.

Parenteral drug delivery

Injection of drugs directly into the body, bypassing the gastrointestinal tract; requires products to be sterile, non-pyrogenic, and free of insoluble materials.

Non-pyrogenic

A requirement for parenteral products meaning they are completely free from fever-inducing substances.

Intravenous (IV) route

Direct administration into a vein providing $100\%$ bioavailability and rapid response; typically limited to solutions or emulsions with particles $< 1\,\mu m$.

Intramuscular (IM) route

Injection into a muscle (typically $1-3\,mL$); often used for controlled-release formulations like aqueous suspensions or oil-based depot injections.

Subcutaneous (SC) route

Injection into the fatty tissue layer below the dermis, usually limited to approximately $1\,mL$, with a slower onset of action than IM or IV.

Intrathecal

Injection directly into the cerebrospinal fluid via the subarachnoid space for drugs that cannot cross the blood-brain barrier.

Moist-heat sterilization

Sterilization in an autoclave using steam under pressure ($121^{\circ}C$ for $15\text{ minutes}$) to denature and coagulate microbial proteins.

Filtration sterilization

Removal of microbes by passing solution through a filter with a pore diameter of $0.22\,\mu m$; preferred for thermolabile (heat-sensitive) products.

Gas sterilization

Sterilization using ethylene oxide or propylene oxide; ethylene oxide alkylates proteins and DNA to disrupt metabolic functions.

Superior rectal vein

The rectal vein that follows the portal drainage route and leads to first-pass hepatic metabolism.

Middle and inferior rectal veins

Rectal veins that provide systemic drainage directly into the inferior vena cava, partially bypassing first-pass hepatic metabolism.

Suppositories

Solid dosage forms inserted into the rectum (approx. $2g$ for adults, $1g$ for pediatric) that melt, soften, or dissolve for local or systemic effects.

Enemas

Injections of fluid into the rectum; categorized as Micro-enemas ($1-20\,mL$) or Macro-enemas ($\ge 50\,mL$).

Cocoa Butter (Theobroma Oil)

A fatty suppository base that melts between $30-35^{\circ}C$ and is susceptible to polymorphism if overheated.

Polymorphism (Suppository Base)

The ability of Cocoa Butter to crystallize into different forms; overheating results in an unstable form with a lower melting point of $25-30^{\circ}C$.

Displacement Value (DV)

The amount of drug that displaces $1g$ of the suppository base; calculated as: $\text{DV} = \frac{\text{weight of drug (g)}}{\text{weight of base displaced (g)}}$.

Stratum Corneum

The outermost sub-layer of the epidermis which serves as the primary barrier and route for drug permeation via intercellular or transcellular pathways.

Transdermal patch

A medicated adhesive patch that delivers drugs через the skin and into the bloodstream to maintain steady therapeutic levels via passive diffusion.

Fick’s first law of diffusion

The mathematical foundation for transdermal systems stating: $\frac{Dm}{Dt} = D \times A \times \frac{C_d - C_r}{X}$.

Lyophilization (Freeze Drying)

A process used to dry heat-sensitive materials by removing water through sublimation under controlled vacuum conditions.

Sublimation

The direct transition of ice (solid) into vapor (gas) without passing through the liquid phase, achieved by reducing pressure below the triple point.

Triple point

The unique thermodynamic condition in which the solid, liquid, and gas phases of water all coexist in equilibrium.

Shell freezing

A freezing method for large volumes where liquid is frozen in a thin shell around the inner circumference of the container to maximize surface area.

Primary drying (Lyophilization)

The stage involving the sublimation of frozen solvent into vapor; after this stage, moisture content is typically around $0.5\%$..

Secondary drying (Lyophilization)

The stage where temperature is slightly increased (to $50^{\circ}C-60^{\circ}C$) to remove remaining bound moisture through desorption.

Hygroscopic

A property of freeze-dried products meaning they are highly porous and readily absorb moisture from the atmosphere.

Nasal mucosa

A thin membrane lining the nasal cavity that traps particles in mucus, warms/humidifies air, and serves as a site for drug absorption.

Cilia

Hair-like projections on mucosal cells that facilitate the unidirectional movement of mucus toward the nasopharynx.

Impaction

A nasal/pulmonary deposition mechanism generally affecting larger particles ($0.5-1\,\mu m$ or steroids) favored by fast flow rates.

Sedimentation

The settling of drug particles under the influence of gravity, typically occurring at slower flow rates.

Diffusion (Brownian motion)

The random movement and deposition of very small particles less than $0.5\,\mu m$ in the nasal or pulmonary tracts.

Metered-Dose Inhaler (MDI)

A device consisting of a canister, actuator, and propellant (CFC or HFA) that releases a predetermined fine mist of medication.

Dry Powder Inhaler (DPI)

A breath-activated device (e.g., Turbuhaler, Accuhaler) that delivers drugs as a cloud of fine particles without requiring propellants.

Alveoli

Mini air sacs in the lungs with a massive surface area and thin membrane surrounded by capillaries for gas exchange and drug absorption.

Jet nebulizers

Machines that use compressed gas to convert liquid medication into a fine mist; they are cheap but require extra tubing and a power point.

Cornea

The clear, dome-shaped front surface of the eye consisting of the epithelium (lipid), stroma (aqueous), and endothelium (lipid).

Lacrimal fluid

Tears produced by glands in the upper eyelid; it has a pH of $7.4$, is isotonic, but has a high turnover rate that clears drugs quickly.

Isotonic

A formulation property where the osmotic pressure is equal to physiological fluids, preventing discomfort upon administration.

Hydroxypropylmethylcellulose (HPMC)

A viscosity-modifying agent added to ocular preparations to increase drug residence time on the eye surface.

Shelf life ($t_{95}$)

The time calculated for a drug to lose $5\%$ of its concentration, marking the period the product remains potent for use.

Half-life ($t_{50}$)

The time required for the concentration of a reactant or drug to be reduced by half.

Arrhenius equation

Mathematical model of drug degradation: $k = Ae^{-\frac{E_a}{RT}}$, where $k$ is the rate constant and $T$ is temperature in Kelvin.

Hydrolysis

The most common chemical degradation process involving the breakdown of drug molecules by water.

Photolysis

The degradation of a drug caused by light energy, particularly shorter UV wavelengths; typically managed with amber glass or aluminum foil.

Vaginal Rugae

Ridges on the internal surface of the vagina that increase surface area for absorption and assist in drug retention.

Vaginal microbiome

The bacterial environment (predominantly Lactobacilli) that produces lactic acid and hydrogen peroxide to maintain an acidic pH of approximately $4.5$.

Pessaries (Ovules)

Solid or semi-solid vaginal dosage forms, such as Flagystatin, that dissolve or melt within the vaginal canal.

Follicular Phase

The menstrual cycle phase (Days $1-14$) characterized by increasing estrogen, a thickening/well-moisturized epithelium, and thin/watery fluid.

Luteal Phase

The menstrual cycle phase (Days $15-28$) characterized by increased progesterone, widening of intercellular channels, and thick/sticky fluid.