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Aspirin is acetylsalicylic acid, a nonsteroidal anti-inflammatory drug that acetylates cyclooxygenase. Its persistent effect on platelet function illustrates the distinction between a drug’s presence in blood and the lifetime of its effect on a cellular target.

Cyclooxygenase refers to the oxygenating activity of prostaglandin-endoperoxide synthases, commonly distinguished as COX-1 and COX-2. These enzymes convert arachidonic acid through prostaglandin intermediates toward products used in local signalling. Their cyclooxygenase and peroxidase reactions are successive catalytic activities, rather than the names of two unrelated complete pathways. ^[ref]

Different tissues can process the common intermediate into different final signals, so inhibiting the upstream enzyme can affect several products at once. COX-1 and COX-2 also differ in their regulation and tissue distribution. A change in enzyme abundance, catalytic inhibition and a change in downstream product formation are related but experimentally distinct observations.

Ibuprofen is a nonsteroidal anti-inflammatory drug acting through cyclooxygenase inhibition. It illustrates how one pathway can influence pain, fever and inflammation while also participating in normal tissue functions.

Naproxen is a nonsteroidal anti-inflammatory drug that reduces prostaglandin synthesis through cyclooxygenase inhibition. Its pharmacological class describes a shared mechanism, while its exposure time course is a separate pharmacokinetics question.

A nonsteroidal anti-inflammatory drug is a drug in the group including ibuprofen, naproxen and aspirin. These agents commonly reduce prostaglandin production through cyclooxygenase inhibition. Their shared pathway does not make their duration, selectivity or other effects identical.