Advanced Pharmacokinetics - Week 1 Flashcards

A set of vocabulary flashcards based on lecture notes covering fundamental pharmacokinetics concepts, drug passage across membranes, pH partitioning, absorption factors, distribution factors, and metabolism.

Pharmacokinetics

The study of drug movement throughout the body.

Absorption

Drug movement from the site of administration into the blood (systemic circulation).

Distribution

Drug movement from blood to the interstitial space of tissues, into cells, and to the site of action.

Metabolism (Biotransformation)

Enzymatically mediated alteration of drug structure, occurring primarily in the liver.

Excretion

Movement of drugs and their metabolites out of the body.

Elimination

The combination of metabolism and excretion.

Channels and Pores

Small and specific membrane pathways for tiny compounds (e.g., sodium, potassium) used by very few drugs.

Transport Systems

Selective carriers that move drugs across biological membranes (e.g., P-glycoprotein / PGP).

P-glycoprotein (PGP)

A transmembrane transport system carrier that functions to pump drugs out of cells.

Direct Penetration

The most common mechanism of drug passage across membranes, requiring a drug to be lipid-soluble (lipophilic) to dissolve into and penetrate membrane lipids.

Polar Molecules

Molecules with no net charge but an uneven charge distribution (e.g., $H_2O$) that dissolve in polar solvents but cannot penetrate nonpolar lipid membranes.

Ions

Molecules that possess a net charge and cannot cross biological membranes unless they are in a nonionized form.

pH Partitioning (Ion Trapping)

The accumulation of acidic drugs on the alkaline side and basic drugs on the acidic side of a membrane, enhanced when site-to-plasma pH differences favor ionization in plasma.

Aspirin Absorption Example

A weak acid drug that is nonionized and absorbed in the acidic stomach (acid + acid = nonionized), but whose absorption is impeded in the alkaline small intestine.

Blood-Brain Barrier (BBB)

A vascular barrier with tight junctions and PGP pumps that limits drug access to the brain, requiring lipid solubility or specific transport, and which is not fully developed at birth.

Placental Transfer

Passage of drugs across the placenta via simple diffusion, permitting lipid-soluble, nonionized compounds while excluding ionized, polar, or protein-bound drugs.

Protein Binding

Reversible binding of drugs to plasma albumin which restricts distribution; competition for binding sites can lead to drug interactions.

Tissue Perfusion Impairments

Conditions such as abscesses (which lack blood vessels) and tumors (which have a limited core blood supply) that impede drug delivery to tissues.