FDA

Mercaptopurine

Approved 26 Feb 2025OralSuspension

The FDA lists this product in 4 strengths and forms.

Indications

Mercaptopurine is a nucleoside metabolic inhibitor indicated for the treatment of patients with acute lymphoblastic leukemia (ALL) as part of a combination chemotherapy maintenance regimen. ( 1.1 )

1.1Acute Lymphoblastic Leukemia

Mercaptopurine is indicated for the treatment of patients with acute lymphoblastic leukemia (ALL) as part of a combination chemotherapy maintenance regimen.

Contraindications

None.

None

Warnings and precautions

Myelosuppression : Monitor complete blood count (CBC) and adjust the dose of mercaptopurine 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-TPMT or homozygous-NUDT15 deficiency may require a dose reduction. ( 2.2 , 5.1 )
Hepatotoxicity : Monitor transaminases, alkaline phosphatase and bilirubin. Withhold mercaptopurine at onset of hepatotoxicity. ( 5.2 )
Immunosuppression : Response to all vaccines may be diminished and there is a risk of infection with live virus vaccines. Consult immunization guidelines for immunocompromised pediatrics. ( 5.3 )
Treatment Related Malignancies : Aggressive and fatal cases of hepatosplenic T-cell lymphoma have occurred. ( 5.4 )
Macrophage Activation Syndrome : Monitor for and treat promptly; discontinue mercaptopurine. ( 5.5 )
Embryo-Fetal Toxicity : Can cause fetal harm. Advise patients of reproductive potential of the potential risk to a fetus and to use effective contraception. ( 5.6 , 8.1 , 8.3 )
Phenylketonuria : Patients should be informed that mercaptopurine oral suspension contains phenylalanine, a component of aspartame. Each mL of the 20 mg/mL oral suspension contains 0.015 mg of phenylalanine. ( 5.7 )

5.1Myelosuppression

The most consistent, dose-related adverse reaction of mercaptopurine is myelosuppression, manifested by anemia, leukopenia, thrombocytopenia, or any combination of these. Monitor CBC and adjust the dosage of mercaptopurine for excessive myelosuppression [see Dosage and Administration ( 2.1 )] . Consider testing for thiopurine S-methyltransferase (TPMT) or nucleotide diphosphatase (NUDT15) deficiency in patients with severe myelosuppression or repeated episodes of myelosuppression.

At a glance

Brand name: Mercaptopurine
Route: Oral
Dosage form: Suspension
Applicant: Hikma
Status: Prescription
FDA approval: 26 Feb 2025
Application: ANDA216418-001

Indications

Mercaptopurine is a nucleoside metabolic inhibitor indicated for the treatment of patients with acute lymphoblastic leukemia (ALL) as part of a combination chemotherapy maintenance regimen. ( 1.1 )

1.1Acute Lymphoblastic Leukemia

Mercaptopurine is indicated for the treatment of patients with acute lymphoblastic leukemia (ALL) as part of a combination chemotherapy maintenance regimen.

Warnings and precautions

Myelosuppression : Monitor complete blood count (CBC) and adjust the dose of mercaptopurine 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-TPMT or homozygous-NUDT15 deficiency may require a dose reduction. ( 2.2 , 5.1 )
Hepatotoxicity : Monitor transaminases, alkaline phosphatase and bilirubin. Withhold mercaptopurine at onset of hepatotoxicity. ( 5.2 )
Immunosuppression : Response to all vaccines may be diminished and there is a risk of infection with live virus vaccines. Consult immunization guidelines for immunocompromised pediatrics. ( 5.3 )
Treatment Related Malignancies : Aggressive and fatal cases of hepatosplenic T-cell lymphoma have occurred. ( 5.4 )
Macrophage Activation Syndrome : Monitor for and treat promptly; discontinue mercaptopurine. ( 5.5 )
Embryo-Fetal Toxicity : Can cause fetal harm. Advise patients of reproductive potential of the potential risk to a fetus and to use effective contraception. ( 5.6 , 8.1 , 8.3 )
Phenylketonuria : Patients should be informed that mercaptopurine oral suspension contains phenylalanine, a component of aspartame. Each mL of the 20 mg/mL oral suspension contains 0.015 mg of phenylalanine. ( 5.7 )

5.1Myelosuppression

Interactions

Allopurinol : Reduce the dose of mercaptopurine when coadministered with allopurinol. ( 2.4 , 7.1 )
Warfarin : Mercaptopurine may decrease the anticoagulant effect. ( 7.2 )

7.1Allopurinol

Allopurinol can inhibit the first-pass oxidative metabolism of mercaptopurine by xanthine oxidase, which can lead to an increased risk of mercaptopurine adverse reactions [see Warnings and Precautions ( 5.1 ), Adverse Reactions ( 6.1 )] . Reduce the dose of mercaptopurine when coadministered with allopurinol [see Dosage and Administration ( 2.4 )] .

7.2Warfarin

The coadministration of mercaptopurine with warfarin may decrease the anticoagulant effectiveness of warfarin. Monitor the international normalized ratio (INR) in patients receiving warfarin and adjust the warfarin dosage as appropriate.

7.3Myelosuppressive Products

Mercaptopurine can cause myelosuppression. Myelosuppression may be increased when mercaptopurine is coadministered with other drugs that cause myelosuppression. Enhanced myelosuppression has been noted in some patients receiving trimethoprim-sulfamethoxazole. Monitor the CBC and adjust the dose of mercaptopurine for excessive myelosuppression [see Dosage and Administration ( 2.1 ), Warnings and Precautions ( 5.1 )] .

7.4Aminosalicylates Aminosalicylates

(e.g., mesalamine, olsalazine or sulfasalazine) may inhibit the TPMT enzyme, which may increase the risk of myelosuppression when coadministered with mercaptopurine. When aminosalicylates and mercaptopurine are coadministered, use the lowest possible doses for each drug and monitor more frequently for myelosuppression [see Warnings and Precautions ( 5.1 )] .

7.5Hepatotoxic Products

Mercaptopurine can cause hepatotoxicity. Hepatotoxicity may be increased when mercaptopurine is coadministered with other products that cause hepatotoxicity. Monitor liver tests more frequently in patients who are receiving mercaptopurine with other hepatotoxic products [see Warnings and Precautions ( 5.2 )] .

7.6Methotrexate

Mercaptopurine dosage may need adjustment when administered concomitantly with high dose methotrexate [see Warnings and Precautions ( 5.1 )] . Mercaptopurine exposure increases with concomitant methotrexate use [see Clinical Pharmacology ( 12.3 )] which may increase the risk of mercaptopurine adverse reactions. The mechanism of this interaction has not been fully characterized [see Clinical Pharmacology ( 12.3 )] .

Adverse reactions

The following clinically significant adverse reactions are described elsewhere in the labeling:

Myelosuppression [see Warnings and Precautions ( 5.1 )]
Hepatotoxicity [see Warnings and Precautions ( 5.2 )]
Immunosuppression [see Warnings and Precautions ( 5.3 )]
Treatment Related Malignancies [see Warnings and Precautions ( 5.4 )]
Macrophage Activation Syndrome [see Warnings and Precautions ( 5.5 )] The most common adverse reaction (>20%) is myelosuppression, including anemia, neutropenia, lymphopenia and thrombocytopenia. Adverse reactions occurring in 5% to 20% of patients include anorexia, nausea, vomiting, diarrhea, malaise and rash. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Hikma Pharmaceuticals USA Inc. at 1-800-962-8364 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

6.1Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Based on multicenter cooperative group ALL trials, the most common adverse reaction occurring in > 20% of patients was myelosuppression, including anemia, neutropenia, lymphopenia and thrombocytopenia.

Adverse reactions occurring in 5% to 20% of patients included anorexia, nausea, vomiting, diarrhea, malaise, and rash. Adverse reactions occurring in < 5% of patients included urticaria, hyperuricemia, oral lesions, elevated transaminases, hyperbilirubinemia, hyperpigmentation, infections, and pancreatitis. Oral lesions resemble thrush rather than antifolic ulcerations. Delayed or late toxicities include hepatic fibrosis, hyperbilirubinemia, alopecia, pulmonary fibrosis, oligospermia and secondary malignancies [see Warnings and Precautions ( 5.1 , 5.2 )] .

Drug fever has been reported with mercaptopurine.

6.2Postmarketing Experience

The following adverse reactions have been identified during postapproval use of mercaptopurine. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. These reactions include: photosensitivity, hypoglycemia, portal hypertension, intrahepatic cholestasis of pregnancy (ICP), pellagra, and erythema nodosum.

Mercaptopurine

Indications

1.1Acute Lymphoblastic Leukemia

Contraindications

Warnings and precautions

5.1Myelosuppression

At a glance

Two medicines in one question?

Mercaptopurine

Indications

1.1Acute Lymphoblastic Leukemia

Contraindications

Warnings and precautions

5.1Myelosuppression

At a glance

Two medicines in one question?

5.2Hepatotoxicity

5.3Immunosuppression

5.4Treatment Related Malignancies Hepatosplenic

5.5Macrophage Activation Syndrome

5.6Embryo-Fetal Toxicity

5.7Risks in Patients with Phenylketonuria

Interactions

7.1Allopurinol

7.2Warfarin

7.3Myelosuppressive Products

7.4Aminosalicylates Aminosalicylates

7.5Hepatotoxic Products

7.6Methotrexate

Pregnancy and breastfeeding

8.1Pregnancy Risk Summary

Adverse reactions

6.1Clinical Trials Experience

6.2Postmarketing Experience

Composition

Strengths and forms

Official product information