General Pharmacology Quiz

General Pharmacology

• Pharmacology is the science of drugs.
• Drugs are substances used to prevent, diagnose, and treat diseases.

Pharmacokinetics

• Pharmacokinetics describes what the body does to a drug.
• This includes absorption, distribution, metabolism, and excretion (ADME).

Absorption

• 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).

Distribution

• 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.

Blood-Brain Barrier & Placental Barrier

• 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 (Biotransformation)

• 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.

Excretion

• 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

• 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).