Credit: Bill Branson
The US Food and Drug Administration (FDA) has approved an oral suspension of mercaptopurine (Purixan), a drug used in combination therapy to treat patients with acute lymphoblastic leukemia (ALL).
Mercaptopurine will now be available as a 20 mg/mL oral suspension.
The drug was originally approved as a 50 mg tablet in 1953 and, since that time, has only been commercially available in this form.
Unfortunately, a 50 mg tablet is not ideal because of the age and weight range of children with ALL.
The tablet does not allow for easy body-surface-area dosing and dose adjustments. In addition, tablets can be difficult to administer to children younger than 6 years of age.
To overcome these issues, physicians have used ad hoc local formulations of mercaptopurine compounded in pharmacies or recommended splitting tablets to provide children with the desired dose.
According to the FDA, offering mercaptopurine as a suspension will allow for more accurate delivery of the desired dose to children with a wide range of weights. And a commercially produced suspension is likely to provide a more consistent dose of 6-mercaptopurine than ad hoc compounded formulations.
The FDA’s approval of mercaptopurine as a 20 mg/mL oral suspension is based on results of a clinical pharmacology study. The goal of the study was to assess the bioequivalence of mercaptopurine from a tablet 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 mg/kg to 2.5 mg/kg (50 mg/m2 to 75 mg/m2) as a single, daily dose.
After initiating mercaptopurine, continuation of appropriate dosing requires periodic monitoring of absolute neutrophil counts and platelet counts to assure sufficient drug exposure and to adjust for excessive hematologic toxicity.
Mercaptopurine is distributed by Rare Disease Therapeutics, Inc., in Nashville, Tennessee. For more details on the drug, see the prescribing information.
