General Pharmacology Quiz

Study Notes

Absorption is the passage of a drug from the site of administration to systemic circulation.
Mechanisms of drug absorption include passive diffusion, carrier-mediated transport (facilitated diffusion and active transport), and endocytosis/exocytosis.
Passive diffusion involves movement of drugs across membranes based on concentration gradients.
Carrier-mediated transport uses protein carriers and can facilitate or actively move substances against a concentration gradient.
Endocytosis and exocytosis involve the cell membrane engulfing or releasing substances.
Factors affecting absorption include route of administration, absorbing surface (vascularity and surface area), pathological conditions (e.g., diarrhea), and drug properties (lipid solubility, ionization).

After absorption, drugs are distributed to one or more of the body's compartments: vascular, vascular-interstitial, and vascular-interstitial-intracellular.
Factors affecting distribution include blood flow to organs, lipid solubility of drugs, plasma protein binding (drugs can be bound in plasma and thus inactive, or free).
Bound forms are inactive, not diffusible, and cannot be metabolized or excreted.
Free forms are active, diffusible, and can be metabolized or excreted.
Drugs can also bind to tissues like the thyroid and salivary glands, concentrating in those areas.

The blood-brain barrier prevents many substances from entering the brain except those that are lipid soluble.
Inflammation may increase permeability of the blood-brain barrier.
The placental barrier may cause teratogenicity during pregnancy.
Drugs may cause neonatal asphyxia during labor, if they pass through the placental barrier.

Metabolism is the conversion of unionized drugs to ionized, water-soluble metabolites to facilitate excretion.
The liver is the primary site of metabolism but other organs, such as the lungs, kidneys, and intestines, can also be involved.
Drug metabolism can lead to activation, inactivation, or conversion to toxic metabolites.
Factors affecting biotransformation include the physiological changes (like age and sex), and pathological factors (like liver cell failure), and enzyme induction or inhibition.

Kidneys are the primary organ for drug excretion.
Excretion through the kidney occurs via glomerular filtration, proximal convoluted tubules (PCT), and distal convoluted tubules, and by other mechanisms like bile and lungs.

Elimination half-life (t1/2) is the time it takes for the plasma concentration of a drug to decrease by 50%.
t1/2 impacts dosage intervals and administration methods (e.g., IV infusions for short half-lives).