On April 28, 2014, the U. S. Food and Drug Administration approved an oral suspension of mercaptopurine (Purixan, NOVA Laboratories Limited). Mercaptopurine is a 20 mg/ml oral suspension. Purixan is indicated for the treatment of patients with acute lymphoblastic leukemia (ALL) as part of a combination regimen.
Mercaptopurine is an integral component of ALL therapy. Successive clinical trials have demonstrated that mercaptopurine contributes to successful maintenance therapy and improved survival of patients with ALL. Mercaptopurine was originally approved as a 50 mg tablet in 1953, and since this approval has only been commercially available as a 50 mg tablet.
Because of the age and weight range of children with ALL, a 50 mg tablet is not ideal. Body surface area dosing and dose adjustments are not easily accomplished with the 50 mg tablet. Tablets are not an ideal dosage form of medication for children less than 6 years. Ad hoc local formulations compounded in pharmacies are commonly used. Alternatively 50 mg tablets are split to provide children with the desired dose.
Compared to tablets, a suspension offers the advantage of more accurately delivering the desired dose to children with a wide range of weights using a consistent administration schedule. A suspension will allow more flexibility in adjusting the dose. A commercially produced suspension is more likely to provide a more consistent dose of 6-mercaptopurine than ad hoc compounded formulations.
The approval was based on one clinical pharmacology study to assess the bioequivalence of mercaptopurine from Purinethol tablet (US listed drug) with that of the mercaptopurine oral suspension in a healthy adult population.
The starting dose of mercaptopurine in multi-agent combination chemotherapy maintenance regimens is 1.5 to 2.5mg/kg (50 to 75 mg/m2) as a single daily dose. After initiating mercaptopurine, continuation of appropriate dosing requires periodic monitoring of absolute neutrophil count (ANC) and platelet count to assure sufficient drug exposure (that is to maintain ANC at a desirable level) and to adjust for excessive hematological toxicity.
Full prescribing information is available at:
Mercaptopurine is distributed by Rare Disease Therapeutics, Inc., Nashville, TN.
Healthcare professionals should report all serious adverse events suspected to be associated with the use of any medicine and device to FDA’s MedWatch Reporting System by completing a form online at http://www.fda.gov/medwatch/report.htm
, by faxing (1-800-FDA-0178) or mailing the postage-paid address form provided online, or by telephone (1-800-FDA-1088).