11-keto methylprednisolone is a metabolite of corticosteroid immunosuppressant methylprednisolone.

Cytarabine ocfosfate (commercial name: Starasid) is a prodrug having stearyl group attached to phosphoric acid at 5' position of arabinose moiety of cytosine arabinoside (Ara-C). This drug is given orally. The mode of action is in the inhibition of DNA synthesis after conversion to Ara-CTP as in Ara-C. The drug is metabolized in the liver, producing the intermediate metabolite, C-C3PCA which is converted to Ara-C gradually. This property results in the maintenance of relatively long time the blood Ara-C levels. This was proved to be active clinically against acute leukemia and MDS.

Epitestosterone (17alpha-hydroxy-4-androsten-3-one) is a naturally occurring epimer of testosterone. It apparently parallels the formation of testosterone, but on the other hand its concentration is not influenced by exogenous administration of testosterone. This fact creates the basis of the present doping control of testosterone abuse. Epitestosterone can be considered as a weak antiandrogen in the term of displacement of androgen from receptor binding and as an efficient inhibitor of 5 alpha-reductase. Epitestosterone exerts androgen receptor-independent neuroprotective activity in vitro.

Hippuric Acid is an acyl glycine produced by the conjugation of benzoic acid and glycine, found as a normal component in urine as a metabolite of aromatic compounds from food. Increased urine hippuric acid content may have antibacterial effects. Hippuric Acid is used therapeutically in the form of its salts (hippurates of calcium and ammonium). It is an ingredient of FDA-approved drug Hiprex (methenamine hippurate tablets USP). Each yellow capsule-shaped tablet of Hiprex contains 1 g Methenamine Hippurate which is the Hippuric Acid Salt of Methenamine (hexamethylene tetramine). The tablet also contains inactive ingredients. Hiprex (methenamine hippurate tablets USP) has antibacterial activity because the methenamine component is hydrolyzed to formaldehyde in acid urine. Hippuric acid has some antibacterial activity and also acts to keep the urine acid. The drug is generally active against E. coli, enterococci and staphylococci. Enterobacter aerogenes is generally resistant. The urine must be kept sufficiently acid for urea-splitting organisms such as Proteus and Pseudomonas to be inhibited. Hiprex is indicated for prophylactic or suppressive treatment of frequently recurring urinary tract infections when long-term therapy is considered necessary.

Acecainide (N-acetylprocainamide), the N-acetylated metabolite of procainamide, is a Class III antiarrhythmic agent. Acecainide exerts cardiac anticholinergic effect. It elicits smooth muscle relaxation mainly through the activation of plasma membrane K+ channels. Acecainide markedly reduced premature ventricular beats and prevented induction of ventricular tachycardia. Acecainide appears to offer advantages over procainamide, particularly with respect to the reduced formation of antinuclear antibodies. Acecainide development has been discontinued.

Nicotinyl methylamide (N-methylnicotinamide) is an experimental drug with no approved indication or marketed formulation. Nicotinyl methylamide is a metabolite of niacin (or nicotinamide) and is commonly found in human urine. However low levels of urinary excretion of N-methylnicotinamide indicates niacin deficiency. In patients with liver cirrhosis nicotinamide methylation is increased leading to a rise in urinary N-methylnicotinamide. The hyperfunction of this methylating pathway might play a protective role against the toxic effect of intracellular accumulation of nicotinamide deriving from the catabolic state of cirrhosis. N-methylnicotinamide is known to inhibit choline transport and reduce choline clearance out of the brain. N-methylnicotinamide has been found to be a microbial metabolite. N-methylnicotinamide inhibits arterial thrombosis in hypertensive rats. N-methylnicotinamide via production/release of prostacyclin inhibits arterial thrombosis development. The antithrombotic effect of N-methylnicotinamide is accompanied by platelet inhibition and enhanced fibrinolysis, due to the decrease production of plasminogen activator inhibitor -1.

Dihydromorphine is a semi-synthetic opioid derived from morphine. dihydromorphine is a moderately strong analgesic and is used clinically in the treatment of pain and is also the active metabolite of dihydrocodeine. Dihydromorphine acts as an agonist at the μ-opioid (mu), δ-opioid (delta) and κ-opioid (kappa) receptors. Dihydromorphone is approved for clinical use in the United States, Europe, and Japan; and sold under the brand name Dilaudid. Similar to morphine, and other morphine derivatives, hydromorphone has a high potential for addiction and abuse and is listed as a Schedule II drug in the United States Controlled Substances Act of 1970 (and similarly regulated in other countries).

MC-1046 (Impurity A of Calcipotriol) is the C22-23-unsaturated 24-ketone, an active metabolite of the synthetic vitamin D analog calcipotriol (calcipotriene, MC 903). Calcipotriene is a ligand of VDR-like receptors approved for topical dermatological use indicated for the treatment of plaque psoriasis. It is approved by FDA in United States under the trade name Dovonex. Calcipotriol displays minimal effects on calcium homeostasis, and regulates cell differentiation, and proliferation exhibiting antiproliferative activity against human HL-60, HL60/MX2, MCF-7, T47D, SCC-25 and mouse WEHI-3 cancer cell lines. Calcipotriol is an effective anti-proliferative agent when applied topically at high concentrations but it is relatively “noncalcemic” in vivo (administered perorally, intravenously or intraperitoneally) because it can be metabolized by a variety of cells to metabolites with reduced biological activity as was demonstrated in vitro using rat and human cell lines from liver, bone, kidney, and keratinocytes. MC1046 is the initial calcipotriol metabolite which concentration reaches a steady state after 4 h of incubation with cells in vitro whereas the concentration of another major MC 903 metabolite MC1080, C22-23-saturated 24-ketone, continues to increase linearly over the time period tested (20 h). These two metabolites have also been detected in vivo in serum from rats and pigs dosed with MC903. MC1046 has the ability to stimulate e VDRE-mediated human growth hormone production in COS-1 cells co-transfected with pSG5hVDR1/3 and (CT4)4TKGH vectors and also binds to VDR although with lower (1/133) binding affinity compared to calcipotriol.