Basics of Biopharmaceutics & Pharmacokinetics Vocabulary Flashcards

Vocabulary practice flashcards covering fundamental concepts in biopharmaceutics and pharmacokinetics, including ADME processes, kinetic equations, distribution principles, and metabolic pathways.

Pharmacokinetics

The study of what the body does to a drug, encompassing the core processes of absorption, distribution, metabolism, and elimination (ADME).

Pharmacodynamics

The study of what a drug does to the body, focusing on efficacy, toxicity, and the magnitude of the biological response.

Minimum Effective Concentration (MEC)

The minimum drug concentration in plasma needed to elicit a desired therapeutic effect.

Minimum Toxic Concentration (MTC)

The lowest drug concentration in plasma at which toxic side effects begin to manifest.

Peak Concentration Level ($C_{\max}$)

The highest plasma concentration of a drug observed after administration.

Time for Peak Concentration ($T_{\max}$)

The total time required after drug administration to reach peak plasma concentration ($C_{\max}$).

Onset Time

The time required after drug administration for plasma concentration to reach the Minimum Effective Concentration (MEC).

Duration of Action

The time interval between the onset time and the moment plasma drug concentration declines back below the Minimum Effective Concentration (MEC).

Therapeutic Range / Window

The concentration range between the Minimum Effective Concentration (MEC) and the Minimum Toxic Concentration (MTC) within which safe therapy is achieved.

Potency

The dose or concentration of a drug required to produce a specific biological effect, where a potent drug elicits response at a low dose.

Efficacy

The maximum physiological response achievable by a drug, represented as the highest plateau on a dose-response curve.

Therapeutic Index (TI)

A measure of drug safety calculated as the ratio of toxic dose to effective dose: $\text{TI} = \frac{\text{TD}_{50}}{\text{ED}_{50}}$.

Enteral Route

A route of drug delivery via the gastrointestinal tract, including oral (PO), rectal (PR), or feeding tubes (NG, NI, PEG).

Parenteral Route

A route of drug administration placed directly into tissues or the systemic circulation by injection (such as IV, IM, SC, IP, or intradermal).

Topical Route

Administration of a drug via the skin or mucous membranes for direct local effect or systemic absorption.

Drug Liberation

The initial step in drug action where a solid dosage form undergoes disintegration, deaggregation, and dissolution into solution.

Noyes-Whitney Equation

An equation defining the rate of solid dissolution into a liquid: $\frac{dm}{dt} = \frac{D_w S}{h} (C_s - C_b)$.

Absorption

The process of transferring an intact drug across cell membranes from its site of administration into the systemic circulation.

Passive Diffusion

The movement of drug molecules across biological membranes down a concentration gradient without requiring cellular energy.

Bioavailability (BA)

The fraction ($F$) of an administered dose of unchanged drug that reaches systemic circulation.

Absolute Bioavailability ($F_{\text{abs}}$)

The systemic drug exposure ratio comparing a non-intravenous dose to an intravenous dose: $F_{\text{abs}} = \frac{\text{AUC}_{0-\infty, \text{oral}} / D_{\text{oral}}}{\text{AUC}_{0-\infty, \text{iv}} / D_{\text{iv}}}$.

Relative Bioavailability ($F_{\text{rel}}$)

The comparison of systemic exposure between Formulation A and Formulation B given by a specific non-IV route: $F_{\text{rel}} = \frac{\text{AUC}_A / D_A}{\text{AUC}_B / D_B}$.

Distribution

The reversible movement and uptake of a drug between the bloodstream and various tissues or fluid compartments of the body.

Capillary Types in Drug Distribution

The three vascular structural classes determining permeability: Continuous (fat, muscle, nervous system), Fenestrated (intestinal villi, glomeruli), and Discontinuous (liver, bone marrow, spleen).

Plasma Protein Binding

The non-covalent binding of drugs to blood proteins like albumin, creating a reservoir that restricts free tissue distribution and elimination.

Total Body Water Compartments

The overall fluid volume breakdown in a standard $70\,kg$ adult, consisting of Intracellular Fluid ($28\,L$) and Extracellular Fluid ($12\,L$, split into $9\,L$ Interstitial Fluid and $3\,L$ Plasma).

Volume of Distribution ($V_d$)

A hypothetical fluid volume into which a drug appears to disseminate in the body, calculated as $V_d = \frac{D}{C}$.

One-Compartment Model

A simple pharmacokinetic model assuming rapid equilibration of a drug throughout a central intravascular volume.

Two-Compartment Model

A pharmacokinetic model used when drugs exhibit slow equilibration between central blood circulation and peripheral tissue spaces.

Steady State

The equilibrium state during multiple dosing achieved when the rate of drug administration equals the rate of drug elimination (rate in = rate out).

Therapeutic Drug Monitoring (TDM)

The practice of measuring plasma drug concentrations to guide individual dosing regimes, ensuring maximum efficacy while preventing toxicity.

Metabolism (Biotransformation)

The chemical alteration of drugs by enzymes (chiefly in the liver) into more polar, water-soluble metabolites suitable for excretion.

Phase I Reactions

Destructive metabolic processes (oxidation, reduction, hydrolysis) catalyzed mainly by Cytochrome P450 enzymes that attach or unmask functional groups.

Phase II Reactions

Synthetic conjugation processes (e.g., glucuronidation, sulfation, acetylation) that attach polar endogenous molecules to enhance water solubility.

First-Pass Effect

The pre-systemic clearance and metabolism of an orally administered drug during passage through the intestinal wall and liver prior to systemic distribution.

Bioequivalence (BE)

The absence of a significant difference in the rate and extent of absorption of an active drug component between generic and brand products under identical conditions.

Cytochrome P450 (CYP) Enzymes

A superfamily of liver enzymes responsible for catalyzing Phase I oxidative metabolism of numerous xenobiotics and drugs.

Glomerular Filtration

The renal process where approximately one-tenth of renal blood flow filters unbound drugs and low molecular weight solutes into the renal tubules.

Zero-Order Kinetics

Reaction kinetics where the rate of drug clearance or elimination is constant and completely independent of reactant drug concentration ($\frac{-dC_0}{dt} = k$).

First-Order Kinetics

Reaction kinetics where the rate of drug elimination or transformation is directly proportional to the current drug concentration ($\frac{-d[C]}{dt} = k[C]$).

Half-Life ($t_{1/2}$)

The duration of time required for the concentration or amount of active drug in the body to decrease by $50\%$.

Arrhenius Equation

An expression showing the dependence of reaction rate constant ($k$) on absolute temperature ($T$) and activation energy ($E_a$): $k = A e^{-\frac{E_a}{RT}}$.

$Q_{10}$ Stability Factor

A factor indicating the ratio by which a drug degradation reaction rate increases for every $10\,^\circ\text{C}$ increase in temperature.