Mercaptopurine

What it is and how it works

Mechanism of Action Mercaptopurine is a purine analog that undergoes intracellular transport and activation to form metabolites including thioguanine nucleotides (TGNs). Incorporation of TGNs into DNA or RNA results in cell-cycle arrest and cell death. TGNs and other mercaptopurine metabolites are also inhibitors of de novo purine synthesis and purine nucleotide interconversions. Mercaptopurine was cytotoxic to proliferating cancer cells in vitro and had antitumor activity in mouse tumor models. It is not known which of the biochemical effects of mercaptopurine and its metabolites are directly or predominantly responsible for cell death.

Indications

Mercaptopurine Tablets is a nucleoside metabolic inhibitor indicated for treatment of adult and pediatric patients with acute lymphoblastic leukemia (ALL) as part of a combination chemotherapy maintenance regimen. Acute Lymphoblastic Leukemia Mercaptopurine Tablets are indicated for treatment of adult and pediatric patients with acute lymphoblastic leukemia (ALL) as part of a combination chemotherapy maintenance regimen.

Dosage and administration (summary)

The recommended starting dose of Mercaptopurine Tablets is 1.5 mg/kg to 2.5 mg/kg orally once daily as part of a combination chemotherapy maintenance regimen. Adjust dose to maintain desirable absolute neutrophil count and for excessive myelosuppression. Renal Impairment: Use the lowest recommended starting dose or increase the dosing interval. (2.3, 8.6) Hepatic Impairment: Use the lowest recommended starting dose. (2.3, 8.7) Recommended Dosage The recommended starting dosage of Mercaptopurine Tablets is 1.5 mg/kg to 2.5 mg/kg orally once daily as part of combination chemotherapy maintenance regimen.

Contraindications

None. None.

Warnings and precautions

Myelosuppression: Monitor complete blood count (CBC) and adjust the dose of Mercaptopurine Tablets for excessive myelosuppression. Consider testing in patients with severe myelosuppression or repeated episodes of myelosuppression for thiopurine S-methyltransferase (TPMT) or nucleotide diphosphatase (NUDT15) deficiency. Patients with homozygous or homozygous TPMT or NUDT15 deficiency may require a dose reduction. (2.2, 5.1) Hepatotoxicity: Monitor transaminases, alkaline phosphatase and bilirubin. Withhold Mercaptopurine Tablets at onset of hepatotoxicity.

Pregnancy

Pregnancy Risk Summary Mercaptopurine Tablets can cause fetal harm when administered to a pregnant woman . Pregnant women who receive mercaptopurine have an increased incidence of miscarriage and stillbirth (see Data). Advise pregnant women of the potential risk to a fetus.

Storage and supply

Mercaptopurine Tablets, USP 50 mg supplied as pale yellow, biconvex tablets, with product identification “54 420” on one side and a score on the other side. NDC 51407-983-25: Bottle of 250 Tablets Store at 20°C to 25°C (68°F to 77°F). Store in a dry place. Dispense in a tight, child-resistant container as defined in the USP/NF.

Source: Mercaptopurine (Mercaptopurine) — US FDA prescribing information, 2026-02-25, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.