Veterinary Drug Handbook (VDH) is the reference veterinarians turn to when they want an independent source of information on the drugs that are used in veterinary medicine today.


Chemistry - A structural analogue of thiamine (vitamin B1), amprolium hydrochloride occurs as awhite or almost white, odorless or nearly odorless powder. One gram is soluble in 2 ml of waterand is slightly soluble in alcohol.

Storage, Stability, Compatibility

Unless otherwise instructed by the manufacturer, amproliumproducts should be stored at room temperature (15-30°C).


By mimicking its structure, amprolium competitively inhibits thiamine utilizationby the parasite. Prolonged high dosages can cause thiamine deficiency in the host and excessivethiamine in the diet can reduce or reverse the anticoccidial activity of the drug.
Amprolium reportedly acts primarily upon the first generation schizont in the cells of the intestinalwall, preventing differentiation of the metrozoites. It may also suppress the sexual stages andsporulation of the oocysts.
Uses, Indications - Amprolium has good activity against Eimeria tenella, E. acervulina in poultryand can be used as a therapeutic agent for these organisms. It only has marginal activity or weakactivity against E. maxima, E. mivati, E. necatrix, or E. brunetti. It is often used in combination withother agents (e.g., ethopabate) to improve control against those organisms.
In cattle, amprolium has approval for the treatment and prevention of E. bovis and E. zurnii incattle and calves. Amprolium has been used in dogs, swine, sheep, and goats for the control ofcoccidiosis, although there are no approved products in the U.S.A. for these species.


No information was located for this agent.

Contraindications, Precautions, Reproductive Safety

Not recommended to be used for over12 days in puppies.

Adverse Effects, Warnings

In dogs, neural disturbances, depression, anorexia, and diarrhea havebeen reported but are rare and are probably dose-related. See Overdosage section below fortreatment recommendations.
Overdosage, Acute Toxicity - Amprolium has induced polioencephalomalacia (PEM) in sheepwhen administered at 880 mg/kg PO for 4-6 weeks and at 1 gram/kg for 3-5 weeks. Erythrocyteproduction in lambs receiving these high dosages of amprolium also ceased.
It is reported that overdoses of amprolium will produce neurologic symptoms in dogs. Treatmentshould consist of stopping amprolium therapy and administering parenteral thiamine (1 - 10mg/day IM or IV).

Drug Interactions

Exogenously administered thiamine in high doses may reverse or reduce theefficacy of amprolium.