Once a complete hematologic remission is obtained, maintenance therapy is considered essential. Maintenance doses will vary from patient to patient. The usual daily maintenance dose of PURINETHOL is 1.5 to 2.5mg/kg/day as a single dose. It is to be emphasized that in pediatric patients with acute lymphatic leukemia in remission, superior results have been obtained when PURINETHOL has been combined with other agents (most frequently with methotrexate) for remission maintenance. PURINETHOL should rarely be relied upon as a single agent for the maintenance of remissions induced in acute leukemia.
Proceduresforproperhandlinganddisposalofanticancerdrugsshouldbeconsidered.Several guide lines on this subject have been published.1-8 There is no general agreement that all of the procedures recommended in the guidelines are necessary or appropriate.
Dosage with Concomitant Allopurinol
When allopurinol and mercaptopurine are administered concomitantly, the dose of mercaptopurine must be reduced to one third to one quarter of the usual dose to avoid severe toxicity.
Dosage in TPMT-deficient Patients
Patients with inherited little or no thiopurine S-methyltransferase (TPMT) activity are at increased risk for severe PURINETHOL toxicity from conventional doses of mercaptopurine and generally require substantial dose reduction. The optimal starting dose for homozygous deficient patients has not been established. (See CLINICAL PHARMACOLOGY, WARNINGS, and PRECAUTIONS sections.)
Most patients with heterozygous TPMT deficiency tolerated recommended PURINETHOL doses, but some require dose reduction. Genotypic and phenotypic testing of TPMT status are available. (See CLINICAL PHARMACOLOGY, WARNINGS, and PRECAUTIONS sections.)
Dosage in Renal and Hepatic Impairment
It is probably advisable to start with lower dosages inpatients with impaired renal function, due to slower elimination of the drug and metabolites and a greater cumulative effect. Consideration should be given to reducing the dosage in patients with impaired hepatic function.
Pale yellow to buff, scored tablets containing 50 mg mercaptopurine, imprinted with “PURINETHOL” and “9|3”; bottles of 25 (NDC 69076-913-02) and bottles of 250 (NDC 69076-913-25).
Store at 2° to 25°C (68°to77°F) [see USP Controlled Room Temperature]. Store in a dry place. Dispense in tight container as defined in USP.
- ONS Clinical Practice Committee. Cancer Chemotherapy Guidelines and Recommendations for Practice. Pittsburgh, PA: Oncology Nursing Society;1999:32-41.
- Recommendations for the safe handling of parenteral antineoplastic drugs. Washington, DC: Division of Safety; Clinical Center Pharmacy Department and Cancer Nursing Services, National Institutes of Health; 1992. US Dept of Health and Human Services. Public Health Service publication NIH92-2621.
- AMA Council on Scientific Affairs. Guidelines for handling parenteral antineoplastics. JAMA.1985;253:1590-1591.
- National Study Commission on Cytotoxic Exposure. Recommendations for handling cytotoxicagents.1987. Available from Louis P. Jeffrey, Chairman, National Study Commission on Cytotoxic Exposure. Massachusetts College of Pharmacy and Allied Health Sciences, 179 Longwood Avenue, Boston, MA 02115.
- Clinical Oncological Society of Australia. Guidelines and recommendations for safe handling of antineoplastic agents. Med J Australia.1983;1:426-428.
- Jones RB, Frank R, Mass T. Safe handling of chemotherapeutic agents: a report from the Mount Sinai Medical Center. CA-A Cancer J for Clinicians. 1983;33:258-263.
- American Society of Hospital Pharmacists. ASHP technical assistance bulletin on handling cytotoxic and hazardous drugs. Am J Hosp Pharm.1990;47:1033-1049.
- Controlling Occupational Exposure to Hazardous Drugs.(OSHA Work-Practice Guidelines.) Am J Health-Syst Pharm.1996;53: 1669-1685.
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