Drug Excretion Lecture Review

Vocabulary-style flashcards covering the mechanism of drug excretion, including renal and biliary pathways and the factors influencing them as discussed in the lecture.

Drug Excretion

The elimination of drugs from the plasma and body, occurring largely through renal pathways, as well as biliary, exhalation, and sweat.

ADME

A pharmacokinetics acronym representing Absorption, Distribution, Metabolism, and Excretion.

Glomerular Filtration

A component of renal excretion where drugs with $MW < 20,000\,Da$ cross the barrier freely, while protein-bound drugs do not.

Active Tubular Secretion

A highly efficient active transport process in the kidneys that utilizes acid and base transporters and can transport plasma protein-bound drugs.

Acid Transporters

Specific transporters involved in active tubular secretion for drugs like Penicillin.

Base Transporters

Specific transporters involved in active tubular secretion for drugs like Pethidine.

Passive Diffusion (Renal Tubule)

A process where water reabsorption increases the concentration of drug in the urine, leading particularly to the reabsorption of lipid soluble drugs.

Digoxin

A polar drug that is not reabsorbed in the renal tubule and relies on effective renal excretion.

Ion Trapping

A phenomenon related to urine pH where ionized drugs are not reabsorbed; for example, basic drugs ionize in acidic urine.

Biliary Excretion

The excretion of polar, high molecular weight drugs or metabolites ($> 250,000\,Da$), such as glucuronides, from hepatocytes into bile and then into faeces.

Vecuronium

An example of a drug that is excreted via biliary excretion into the faeces.

Enterohepatic cycling

The process involving hydrophilic drugs (glucuronides) where the conjugate is hydrolyzed, allowing the reabsorption of the active drug and creating a reservoir that prolongs drug action.

Morphine

A drug that undergoes enterohepatic cycling, which acts as a reservoir to prolong its action.

Factors affecting Renal Excretion in Age

Changes including decreased renal mass, decreased renal blood flow, decreased GFR, and decreased tubular absorption.

Factors affecting Renal Excretion in Neonates

Conditions including low GFR, high total body water content, immature kidney morphology, and decreased plasma protein binding.