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Mercaptopurine information from DrugsUpdate  

See Available Brands of Mercaptopurine in India

P - Contraindicated in pregnancy
L - Contraindicated in lactation

Mercaptopurine (also called 6-mercaptopurine, 6-MP or its brand name Purinethol) is an immunosuppressive drug.

It is a thiopurine.

Pharmacodynamics

Pharmacokinetics

Mercaptopurine is a purine antagonist which is converted intracellularly into its active nucleotides, including thioinosinic acid. The nucleotides inhibit several reactions which ultimately interferes with nucleic acid synthesis and prevents the formation of RNA and DNA.

Absorption

Variable and incomplete; peak plasma concentrations within 2 hours (oral).

Distribution
Widely distributed; crosses the blood-brain barrier and CSF.

Metabolism
Hepatic by methylation, oxidation and formation of inorganic sulfates.

Excretion
Urine (as metabolites and unchanged drug).

Mercaptopurine Indications / Mercaptopurine Uses

Information Not Available

Mercaptopurine Adverse Reactions / Mercaptopurine Side Effects

Hyperuricaemia, bone marrow toxicity, hypoplasia, anorexia, diarrhoea, leukopenia, thrombocytopenia, intestinal ulceration, crystalluria with haematuria, immunosuppression, interstitial pneumonitis. Cutaneous hyperpigmentation, alopecia.

Potentially Fatal: Myelosuppression; hepatotoxicity, cholestatic jaundice.

Precautions

The safe and effective use of Mercaptopurine demands close monitoring of the CBC and patient clinical status. After selection of an initial dosage schedule, therapy will frequently need to be modified depending upon the patient’s response and manifestations of toxicity. It is probably advisable to start with lower dosages in patients with impaired renal function, due to slower elimination of the drug and metabolites and a greater cumulative effect.

Special Precautions

Hepatic or renal dysfunction; monitor hepatic function periodically. Mercaptopurine is potentially carcinogenic. Thiopurine S-methyl transferase (TPMT) deficiency; porphyria.

Other Drug Interactions

Anticoagulant action of warfarin may be inhibited by mercaptopurine. Enhanced toxicity with myelosuppressive drugs.

Potentially Fatal: Effects enhanced by allopurinol (reduce dose of mercaptopurine). Other hepatotoxic drugs (e.g. doxorubicin) potentiate toxicity.

Other Interactions

Information Not Available

Dosage

Oral
Acute lymphatic leukaemia
Adult: Usual maintenance dose: Initially, 1.5-2.5 mg/kg daily as a single dose, usually used in combination with methotrexate. Dose may vary individually based on response and tolerance. Monitor blood counts at least once weekly. Withdraw treatment immedietely if there is a sharp drop in the white cell count or severe bone-marrow depression. May resume treatment slowly and carefully if white cell count remains constant for 2-3 days or rises. Reduce dose when used with allopurinol.
Child: Usual maintenance dose: Initially, 1.5-2.5 mg/kg daily as a single dose, usually used in combination with methotrexate. Dose may vary individually based on response and tolerance. Monitor blood counts at least once weekly. Withdraw treatment immedietely if there is a sharp drop in the white cell count or severe bone-marrow depression. May resume treatment slowly and carefully if white cell count remains constant for 2-3 days or rises. Reduce dose when used with allopurinol.

Renal impairment: Dosage may need to be reduced.
Hepatic impairment: Dosage may need to be reduced

Oral
Crohn's disease
Adult: Initially 1-1.5 mg/kg daily, may increase to 125 mg daily.
Child: Initially 1-1.5 mg/kg daily increased to a max of 75 mg daily

Renal impairment: Dosage may need to be reduced.
Hepatic impairment: Dosage may need to be reduced.

Special Populations
Dosage adjustment in patients with thiopurine-S-methyl transferase (TPMT) deficiency to prevent life-threatening myelotoxicity. For patients with homozygous TPMT deficiency: Substantial reduction is required. For patients with heterozygous TPMT deficiency: Some may require reduction but most will tolerate the usual dosages.

Food(before/after)

Should be taken on an empty stomach. (Best taken on an empty stomach 1 hour before or 2 hours after meals. Ensure adequate fluid intake.)

List of Contraindications

Mercaptopurine and Pregnancy

Contraindicated in pregnancy

Category D: There is positive evidence of human foetal risk, but the benefits from use in pregnant women may be acceptable despite the risk (e.g., if the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective).

Mercaptopurine and Lactation

Contraindicated in lactation

Mercaptopurine and Children

Information Not Available

Mercaptopurine and Geriatic

Use with caution because of the greater frequency of decreased hepatic, renal, or cardiac function, and concomitant diseases or other drug therapy. Start at the low end of the dosing range.

Mercaptopurine and Other Contraindications

Pregnancy and lactation. Prior resistance to mercaptopurine or thioguanine; severe liver disease; severe bone marrow suppression.

Storage

Oral
Store at 20-25°C

Lab interference

Oral
Store at 20-25°C

Mercaptopurine brands in India:

6 MP Empurine Mercapto Mesna Puri- Nethol Purinetone

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