The effect of tetracycline on late stage African trypanosomiasis was examined in an in vivo
experiment using rats infected with Trypanosoma brucei brucei
. Infected rats were treated on the 5th
day of infection with 10mg/kg and 20mg/kg rat weight of tetracycline and tetracycline hydrochloride. Tetracycline at 10mg/kg extended the life-span of infected rats from 6 days to 11 days, but with 20mg/kg the rats died on day 6. Tetracycline-HCl at 10 and 20mg/kg extended the life-span to 9 and 12 days respectively. The trypanocidal effect of tetracycline on late stage trypanosomiasis is probably due to its ability to penetrate the blood brain barrier and its probable role in inhibiting ribonucleotide reductase through iron chelation. We suggest that tetracycline-HCl and low concentrations of tetracycline can be used in the clinical management of African Trypanosomiasis.