Pharmacology - PK Concepts (Vocabulary)

Vocabulary flashcards covering key pharmacokinetic concepts from the notes.

Bioavailability

Fraction of an administered drug that reaches systemic circulation; IV is 100%, PO is lower due to absorption and first-pass metabolism.

First-pass effect

Metabolism that reduces drug amount before it reaches systemic circulation, typically occurring with oral administration in the liver and gut.

Route of administration impact

The route (IV vs PO) determines how much drug becomes available in circulation; IV bypasses first-pass and yields higher bioavailability.

Unbound (free) drug

The portion of a drug not bound to plasma proteins; this fraction can cross membranes and produce a pharmacologic effect.

Protein-bound drug

A drug bound to plasma proteins (e.g., albumin); generally inactive and not readily distributed to sites of action.

Protein binding competition and toxicity

When two highly protein-bound drugs compete for limited binding sites, increased free drug can cause toxicity or unpredictable effects.

Blood-brain barrier (BBB)

Selective barrier that limits drug entry into the brain; only certain drugs cross depending on properties and protein binding.

Local (topical) administration

Applied to a specific area (e.g., hydrocortisone cream) to produce local effect with limited systemic absorption.

Nitroglycerin formulations

Certain formulations can be absorbed systemically and provide longer duration of action.

Prodrug

An inactive compound that is metabolized in the body to an active drug.

Metabolism variability

Genetic and enzymatic differences cause some people to metabolize drugs faster or slower (fast vs slow metabolizers).

Grapefruit juice interaction

Grapefruit juice can inhibit drug-metabolizing enzymes, increasing drug levels and prolonging action.

Diet and drug effect

Dietary changes can alter drug levels by changing absorption or metabolism.

Baseline liver function

Baseline liver enzyme tests to assess hepatic function before starting medications that can affect the liver.

Excretion routes

Drugs are excreted primarily by the kidneys (glomerular filtration) but can also be excreted via the liver/bile and enterohepatic pathways.

Enterohepatic recirculation

A cycle where fat-soluble drugs are excreted into bile, reabsorbed from the intestine, returned to the liver, and excreted again, prolonging presence.

Therapeutic buildup

Some drugs require a steady, repeated dosing over weeks to reach a therapeutic concentration and full effect.

Start low and go slow (older adults)

In older adults, begin with the lowest dose and increase gradually to monitor tolerance and response.

Free vs bound drug for action and excretion

The free (unbound) drug is the active form that can reach targets and be excreted; bound drug acts as a reservoir and is inactive.