Mercapurin

Mercapurin Uses, Dosage, Side Effects, Food Interaction and all others data.

Mercapurin 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.

Mercapurin is one of a large series of purine analogues which interfere with nucleic acid biosynthesis and has been found active against human leukemias. It is an analogue of the purine bases adenine and hypoxanthine. It is not known exactly which of any one or more of the biochemical effects of mercaptopurine and its metabolites are directly or predominantly responsible for cell death.

Trade Name Mercapurin
Availability Prescription only
Generic Mercaptopurine
Mercaptopurine Other Names Mercaptopurina, Mercaptopurine, Mercaptopurinum, Mercapurin
Related Drugs methotrexate, doxorubicin, imatinib, Gleevec, Adriamycin, Sprycel
Type
Formula C5H4N4S
Weight Average: 152.177
Monoisotopic: 152.015666838
Protein binding

Plasma protein binding averages 19% over the concentration range 10 to 50 µg/mL (a concentration only achieved by intravenous administration of mercaptopurine at doses exceeding 5 to 10 mg/kg).

Groups Approved
Therapeutic Class Cytotoxic Chemotherapy
Manufacturer
Available Country
Last Updated: September 19, 2023 at 7:00 am
Mercapurin
Mercapurin

Uses

Mercapurin is used for maintenance therapy of acute lymphatic (lymphocytic, lymphoblastic) leukemiaas part of a combination regimen. The response to this agent depends upon the particular subclassification of acute lymphatic leukemia and the age of the patient (pediatric or adult).

Mercapurin is not effective for prophylaxis or treatment of central nervous system leukemia. Mercapurin is not effective in acute myelogenous leukemia, chronic lymphatic leukemia, the lymphomas (including Hodgkins Disease), or solid tumors.

Mercapurin is also used to associated treatment for these conditions: Acute Lymphoblastic Leukaemias (ALL), Acute Promyelocytic Leukemia (APL), Crohn's Disease (CD), Hepatitis, Autoimmune, Lymphoma, Lymphoblastic, Ulcerative Colitis

How Mercapurin works

Mercapurin competes with hypoxanthine and guanine for the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) and is itself converted to thioinosinic acid (TIMP). TIMP inhibits several reactions that involve inosinic acid (IMP), such as the conversion of IMP to xanthylic acid (XMP) and the conversion of IMP to adenylic acid (AMP) via adenylosuccinate (SAMP). Upon methylation, TIMP forms 6-methylthioinosinate (MTIMP) which inhibits glutamine-5-phosphoribosylpyrophosphate amidotransferase in addition to TIMP. Glutamine-5-phosphoribosylpyrophosphate amidotransferase is the first enzyme unique to the de novo pathway for purine ribonucleotide synthesis. According to experimental findings using radiolabeled mercaptopurine, mercaptopurine may be recovered from the DNA in the form of deoxythioguanosine. In comparison, some mercaptopurine may be converted to nucleotide derivatives of 6-thioguanine (6-TG) via actions of inosinate (IMP) dehydrogenase and xanthylate (XMP) aminase that convert TIMP to thioguanylic acid (TGMP).

Dosage

Mercapurin dosage

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

Acute lymphocytic leukemia:

  • 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 wkly. 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 wkly. 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.

Should be taken on an empty stomach. Best taken on an empty stomach 1 hr before or 2 hr after meals. Ensure adequate fluid intake.

Side Effects

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

Toxicity

Signs and symptoms of overdosage may be immediate such as anorexia, nausea, vomiting, and diarrhea; or delayed such as myelosuppression, liver dysfunction, and gastroenteritis. The oral LD50 of mercaptopurine was determined to be 480 mg/kg in the mouse and 425 mg/kg in the rat.

Precaution

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

Interaction

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

Food Interaction

  • Drink plenty of fluids.
  • Take on an empty stomach.

[Moderate] ADJUST DOSING INTERVAL: Limited data suggest that food may decrease the oral bioavailability of 6-mercaptopurine (6-MP).

In one study, the pharmacokinetics of 6-MP were studied on two separate occasions in seven patients.

A single dose of 6-MP was administered after an overnight fast on one occasion and 15 minutes after a standard breakfast on the other.

The authors reported that peak plasma levels of 6-MP were lower and took longer to reach following administration in the fed state.

In addition, plasma levels were undetectable (less than 20 ng
MANAGEMENT: Until more information is available regarding the effect of food on 6-MP absorption, it may be advisable to take 6-MP on an empty stomach 1 hour before or 2 hours after a meal.

Volume of Distribution

The volume of distribution exceeded that of the total body water.

Elimination Route

Clinical studies have shown that the absorption of an oral dose of mercaptopurine in humans is incomplete and variable, averaging approximately 50% of the administered dose. The factors influencing absorption are unknown.

Half Life

Triphasic: 45 minutes, 2.5 hours, and 10 hours.

Pregnancy & Breastfeeding use

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).

Contraindication

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

Special Warning

Renal Impairment: Dosage may need to be reduced.

Hepatic Impairment:

  • Crohn's disease: Dosage may need to be reduced.
  • Acute lymphocytic leukemia: Dosage may need to be reduced

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.

Storage Condition

Store at 20-25° C

Innovators Monograph

You find simplified version here Mercapurin

Mercapurin contains Mercaptopurine see full prescribing information from innovator Mercapurin Monograph, Mercapurin MSDS, Mercapurin FDA label

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