Clozapine N-oxide is the major metabolite of Clozapine and is blood-brain barrier permeable. Clozapine N-oxide is an agonist of DREADDs and activates the DREADD receptors hM3Dq and hM4Di. Clozapine N-oxide is also a dopamine antagonist and selective muscarinic M4 receptor agonist.

Nicotinamide N-oxide (Nicotinamide 1-oxide) is recognized as an in vivo metabolite of nicotinamide which is a precurser of nicotinamide-adenine dinucleotide (NAD+) in animals. The enzyme that catalyzes the reduction of nicotinamide N-oxide to nicotinamide in the liver is xanthine oxidase.

Ampyrone (4-Aminoantipyrine) is a reagent for glucose determination in the presence of peroxidase and phenol.

Isonicotinic acid, a metabolite of isoniazid and a useful isomer of nicotinic acid, is formed from isoniazid by hydrazinolysis and can be catalyzed by cytochrome P450 enzymes, such as CYP2C.

Monobutyl phthalate, the main metabolite of dibutyl phthalate, is an embryotoxin with antiandrogenic properties.

4-Methylamino antipyrine, an active metabolite of Metamizole, a pyrazolone non-steroidal anti-inflammatory drug (NSAID) that inhibits COX, possesses analgesic, antipyretic, and relatively weak anti-inflammatory properties.

Nortriptyline hydrochloride (ELF-101 hydrochloride) is a metabolite of AMITRIPTYLINE that is also used as an antidepressive agent. Nortriptyline is used in major depression, dysthymia, and atypical depressions.

Oseltamivir acid (GS4071) is a potent influenza virus neuraminidase inhibitor and the prodrug of GS4071.