Amprolium

Amprolium is a synthetic coccidiostat used to prevent and control coccidiosis in poultry and other birds. It belongs to the thiamine antagonists, a class of anticoccidial drugs that interfere with the parasite’s uptake of thiamine (vitamin B1). By competing with thiamine, amprolium inhibits thiamine utilization in the intracellular stages of Eimeria species, slowing growth and replication without immediate parasite death.

The drug is active against several Eimeria species that affect chickens, including E. acervulina, E. maxima, E. tenella, and E. brunetti. It is typically administered via medicated feed or drinking water at preventive levels, and may be used as a treatment under veterinary guidance during an outbreak per label directions.

Usage and management: Amprolium is commonly used as a feed additive or water medication and is often included in rotation programs with other anticoccidials to reduce the risk of resistance. Proper mixing and adherence to label directions are important, and some regimens employ combinations with other anticoccidial agents.

Safety and regulatory: Amprolium is generally well tolerated at recommended doses. Overdosage or prolonged administration can lead to thiamine deficiency in the host and neurologic signs. Withdrawal periods before slaughter vary by jurisdiction; operators should follow product labeling and local regulatory guidance.

Resistance and notes: Like other anticoccidials, resistance can develop with improper use, so responsible dosing, rotation, and monitoring are recommended as part of an integrated coccidiosis management plan.