Effect of polyethylene glycol on single and combined topical application of diminazene aceturate (Berenil®) and metronidazole (Metrodine®) in Trypanosoma brucei- and T. congolense-infected mice

The effect of polyethylene glycol on single and combined topical applications of Berenil® and Metrodine® in Trypanosoma brucei- and Trypanosoma congolense-infected mice was evaluated. Parasitaemia in T. brucei group A was cleared by day 24 post-infection (p.i.) following topical application of Berenil® (3.5 mg/kg) in polythene glycol. In group B, Berenil® given intraperitoneally caused parasite clearance by day 12 (p.i.). Topical application of 16 mg/kg of Metrodine® in polyethylene glycol (group C) or orally (group D) caused a decline in parasitaemia by day 36 (p.i.). The combinations of both drugs in polythene glycol topically (group E) and intraperitoneally/orally (group F) cleared parasitaemia within 24 h. In their infected control (group G), parasitaemia disappeared by day 20 and reappeared by day 32 (p.i.). For T. brucei groups A, C, E and F, packed cell volume (PCV) declined by day 8 and appreciated by day 36 (p.i.). In group B, it did so by day 4 and appreciated by day 36 (p.i.). In group D, it did so by day 36 (p.i.) and appreciated slightly. In group G, it declined by day 32 (p.i.). For T. congolense groups A and B, parasite clearance was achieved by day 24 (p.i.). In groups C and D, it was by days 40 and 52 (p.i.), respectively. In groups E and F, it was by day 20 (p.i.). In group G, it increased by day 40 (p.i). In T. congolense groups A and B, PCV declined by day 20 and in group C by day 24. In group D, it did so by day 36 (p.i). The pre-infection PCV values for groups A–D were attained by day 52 (p.i.). In groups E and F, it did so by day 16, but appreciated by day 32 (p.i.). In group G, it did so by day 40 (p.i.). The vital organs of the infected controls showed degenerative changes. In conclusion, polyethylene glycol caused topical absorption of the drugs which were more effective in combinations.