OIA1013 (TERMS) DRUG ABSORPTION

Drug Absorption

Movement of drugs into the central compartment.

Bioavailability

Fraction of administered drug reaching systemic circulation.

Small Intestine

Primary site for drug absorption in humans.

Plicae Circularis

Folds in the intestine increasing surface area.

Villi

Finger-like projections enhancing intestinal absorption.

Passive Diffusion

Movement of drugs across membranes without energy.

Active Transport

Energy-dependent movement of larger drug molecules.

Physicochemical Factors

Drug properties affecting absorption rate and extent.

Gastrointestinal Transit Time

Time drugs spend in the gastrointestinal tract.

GIT pH

Acidity affecting drug dissolution and absorption.

Gastric Emptying

Rate at which stomach contents enter the intestine.

Bile Fluid

Enhances absorption of fats and fat-soluble vitamins.

Bacterial Microflora

Gut bacteria aiding in drug metabolism and absorption.

Lymphatic Absorption

Absorption route for highly lipophilic drugs.

Intestinal Drug Transporters

Proteins mediating drug uptake and efflux.

Drug Stability

Resistance to degradation in gastrointestinal environments.

Disintegration

Process of dosage form breaking into smaller particles.

Dissolution

Rate at which drug dissolves in gastrointestinal fluids.

Ionization State

Charge of a drug affecting its absorption.

Molecular Weight (MW)

Higher MW reduces drug bioavailability.

Lipophilicity

Drug's affinity for lipid environments.

Log P

Partition coefficient for neutral compounds' lipophilicity.

Log D

Distribution coefficient considering ionization at pH.

Excipients

Inactive substances aiding drug formulation and absorption.

Saquinavir

Antiretroviral requiring food for enhanced absorption.

Griseofulvin

Best absorbed with high-fat meals.

Transport Proteins

Facilitate drug movement across biological membranes.

First-Pass Metabolism

Drug metabolism occurring before systemic circulation.

Physicochemical interactions

Influence drug dissolution, stability, and bioavailability.

Enteric coating

Material allowing drug release in the small intestine.

Delayed-release component

Allows repeated action of medication over time.

Enteric polymers

Remain insoluble at low pH, dissolve at pH 5.0-5.5.

Sustained release

Delivers drug at a programmed rate over time.

pH

Measure of hydrogen ion concentration in solution.

pKa

pH where half molecules are ionized, half unionized.

Henderson-Hasselbalch equation

Relates pH, pKa, and ionization of weak acids/bases.

pH partition theory

Ionized and unionized drug concentrations vary by pH.

Drug-drug interactions

Altered drug response due to co-administered drugs.

Pharmacokinetic interactions

Change plasma drug concentrations affecting efficacy.

Pharmacodynamic interactions

Synergism or antagonism between co-administered drugs.

Drug-disease interactions

Drugs beneficial in one disease may harm another.

Drug-nutrient interactions

Nutrients alter drug effects and absorption.

Inhalation absorption

Fast absorption via large surface area in lungs.

Sublingual absorption

Rapid entry into circulation via superior vena cava.

Subcutaneous absorption

Influenced by drug properties and injection factors.

Intramuscular absorption

Rate affected by drug lipophilicity and muscle factors.

Intraperitoneal absorption

Absorbed into mesenteric vessels, may undergo metabolism.

Rectal absorption

Upper rectum undergoes first-pass metabolism; lower bypasses.

Transdermal absorption

Drug penetrates skin for systemic circulation.

Transepidermal pathway

Route for drug penetration through the skin.

Transappendegeal pathway

Alternative route for drug absorption via skin appendages.

Hydrophilic solutes

Transported via intracellular route in skin.

Lipophilic solutes

Diffuse through inter-cellular spaces in skin.

Aspirin pKa

Weak acid with pKa of 4.5, absorbed in stomach.

Strychnine pKa

Weak base with pKa of 9.5, absorbed in G.I. tract.