Potency and stability of compounded formulations of chlorambucil, melphalan and cyclophosphamide

Background: Oral chemotherapy agents are frequently compounded in veterinary medicine however, the potency of some formulations have been shown to vary from that of Food and Drug Administration (FDA)-approved products. Aims: The objective of this study was to evaluate the potency and stability of three compounded oral chemotherapeutics commonly prescribed to be administered over time. Materials & Methods: Compounded chlorambucil 1 mg, cyclophosphamide 5 mg and melphalan 1 mg were obtained and for potency tested upon receipt and 6 weeks later. Results: Potency ranged from 71 to 104% for chlorambucil and 58 to 109% for melphalan; 1/4 and 2/4 samples were <90% of labelled strength at baseline and 6 weeks, respectively, for both drugs. Potency of cyclophosphamide ranged from 92 to 107% with all samples +/−10% of labelled strength at all time points. Discussion/Conclusion: These results demonstrate variability of compounded chemotherapy products, and highlight the need to consider both potency and stability when prescribing orally compounded chemotherapy.