creation date: 2026-08-14 22:31
tags: PharmacologyIncomplete
Pharmacology Concepts
Pharmacodynamics
Absorption
Drug permeation: aqueous diffusion through pores (MW≤200, larger in kidney, near none in BBB), lipid diffusion (nonpolarity ∝ diffusion speed), facilitated diffusion + active transport (organic ions, substance like natural occurring substance), endo/exocytosis (rare)
pH: unionized form can dikuse across membrane
- Calculate proportion of drug uncharged for given pH:
- pH = pKa + log([A-]/[HA]) OR pH = pKa + log([B][BH+])
- Generally: weak acids absorbed well stomach, weak base in intestine → however, larger SA of intestine = absorb both
Distribution
Drug can be: protein bound, in tissue reservoirs, at unwanted sites of
action → affects:
- Circulating [drug]: more extravascular distribute = low plasma [drug]
- Lipid solubility: cross BBB/placenta if unionized
- Drug reservoirs: sequestration of drugs by plasma protein, intracellular proteins, adipose tissue, bone
- Breast milk: lipid-soluble / P-glycoprotein active transport → infant
Metabolism (aka biotransformation)
In liver: inactivate/polarize for elimination OR activate prodrug
- First pass: stomach/intestine → metabolism THEN systemic circ
Bioavailability: % of drug in systemic circulation compared to administered
Phase I: add polar group, CYP450, amine oxidase, ADH, hydrolysis
Phase II: conjugation with endogenous compounds (form excretable)
- Enzymes → genetic variability; induce/inhibit → decreases effect/toxicity
Elimination
Renal excretion → many transporters; rate affected by kidney function
- Urine pH: basic urine → increased acid excretion ; acidic urine → increased base excretion
- Urine flow: diuretics/fluids
- Modulate mechanisms: drugs can block excretion transporters
GI excretion: via bile → endogenous conjugates cleaved by bacteria → reabsorption to systemic circulation (enterohepatic reabsorption)
- Broad spectrum abx → removes reabsorb process → lower levels
Pharmacokinetics
Plateau principle: time to plateau [drug] = 5 * t1/2
- To double Cp → double infusion rate (R)
Vd: apparent volume of distribution → varies w/ each drug
- Larger Vd = more tissue involvement (plasma → all tissue)