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.

Tulipalin A (α-methylene-γ-butyrolactone) (2-Methylenebutyrolactone) which has some phytotoxicity is a natural compound extracted from Tulipa gesneriana.

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.

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.