University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

377

Pages:

2
Author:

Mariam A. A.

Pharmacokinetic Calculations Bioavailability: % of a given dose of a drug that gains access to the systemic circulation Bioavailability depends on absorption from GIT, 1st pass metabolism, hepatic clearance Relative bioavailability: Compares different routes of administration Bioequivalence: Two or more drugs that have the same active ingredients and desired effects Volume of distribution (Vd): Vd = Q / Cp Clearance: Rate of elimination of drug from plasma Steady-state concentration (Css): Rate of input = Rate of output Required for the min. effective concentration and max safe concentration Compare 1st order vs. 0 order kinetics 1st order: A constant proportion of drug eliminated per unit time 0 order: A constant amount of drug metabolized per unit time 1st order: Half-life is constant 0 order: Half-life decreases with plasma concentration Pharmacokinetic Models Explain the one-compartment model & the two-compartment model Single drug enters and exits like the whole body acts as a single volume Linear relationship between Cp and time Two compartment: Drug equilibrates within different tissues at different rates Whole body consists of a central and peripheral compartment Two phases: Distribution and elimination Calculations: Ct = Co * e^(-kt) k = ln(2) / t½ t½ = 0.693 * Vd / CL Clearance (CL) = (plasma conc. * Vd) / (total amount of drug) Amount = V * concentration Rate of elimination constant: Fraction of drug eliminated by unit time