Amprolium is an anti-protozoal drug and in chemical structure analogue
to thiamine (vitamin B1). It inhibits the use of thiamine by the protozoal
parasites. Amprolium competitively inhibits the active transport of
thiamine in isolated second-generation schizonts of Eimeria spp. and in
host intestinal cells. Upon ingestion of amprolium, the coccidia
experience thiamine deficiency and starve from malnutrition.