ADMET

ADMET is the checklist for everything that happens to a drug inside the body besides hitting its target. The letters stand for Absorption, Distribution, Metabolism, Excretion, and Toxicity. If potency answers 'does the molecule work on the protein?', ADMET answers 'can it actually reach that protein, stay long enough, and leave without causing harm?'

Each letter is a stage in the molecule's journey. Absorption is whether it gets into the bloodstream, often from the gut. Distribution is where it travels and what it binds along the way. Metabolism is how the liver and other tissues chemically alter it. Excretion is how it leaves, mainly through urine and bile. Toxicity covers the harm it may do on or off target. A molecule can be beautifully potent and still fail on any one of these.

Medicinal chemists optimize ADMET in parallel with potency, because a drug that is perfectly potent but poorly absorbed or quickly cleared is useless as a pill. Many ADMET properties are estimated early with cheap in vitro assays and computational predictions, but these are approximations; the body is far more complex than any single assay, so surprises in animals and humans are common.