Degradation of berenil (diminazene aceturate) in acidic aqueous solution

Abstract

Abstract The trypanocide berenil was assessed for chemical stability over the pH range 1–8 at 37°C and 0.2 m ionic strength. It was found to be sufficiently unstable under acid conditions that its therapeutic efficacy is most likely severely compromised when administered orally. At pH 3, the half-life was 35 min, decreasing to 1.5 min at pH 1.75. Reaction rate constants were corrected for the effects of buffer catalysis and were found to range from 2.00 min−1 at pH 1 to 6.1 × 10−6 min−1 at pH 8. The pH-rate profile displayed a region (pH 1–4) where specific acid catalysis was dominant, followed by a transitional region (pH 5–7), and finally a region (pH > 7) where uncatalysed degradation was most important. It is recommended that berenil be enteric coated for formulations to be used in treating Third World parasitic diseases.