Chemistry - A structural analogue of thiamine (vitamin B1), amprolium hydrochloride occurs as a white or almost white, odorless or nearly odorless powder. One gram is soluble in 2 ml of water and is slightly soluble in alcohol.
Storage/Stability/Compatibility - Unless otherwise instructed by the manufacturer, amprolium products should be stored at room temperature (15-30°C).
Pharmacology - By mimicking its structure, amprolium competitively inhibits thiamine utilization by the parasite. Prolonged high dosages can cause thiamine deficiency in the host and excessive thiamine 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 intestinal wall, preventing differentiation of the metrozoites. It may also suppress the sexual stages and sporulation of the oocysts.
Uses/Indications - Amprolium has good activity against Eimeria tenella, E. acervulina in poultry and can be used as a therapeutic agent for these organisms. It only has marginal activity or weak activity against E. maxima, E. mivati, E. necatrix, or E. brunetti. It is often used in combination with other 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 in cattle and calves. Amprolium has been used in dogs, swine, sheep, and goats for the control of coccidiosis, although there are no approved products in the U.S.A. for these species.
Pharmacokinetics - No information was located for this agent.
Contraindications/Precautions/Reproductive Safety - Not recommended to be used for over 12 days in puppies.
Adverse Effects/Warnings - In dogs, neural disturbances, depression, anorexia, and diarrhea have been reported but are rare and are probably dose-related. See Overdosage section below for treatment recommendations.
Overdosage/Acute Toxicity - Amprolium has induced polioencephalomalacia (PEM) in sheep when administered at 880 mg/kg PO for 4-6 weeks and at 1 gram/kg for 3-5 weeks. Erythrocyte production in lambs receiving these high dosages of amprolium also ceased.
It is reported that overdoses of amprolium will produce neurologic symptoms in dogs. Treatment should consist of stopping amprolium therapy and administering parenteral thiamine (1 - 10 mg/day IM or IV).
Drug Interactions - Exogenously administered thiamine in high doses may reverse or reduce the efficacy of amprolium.
a) 100 - 200 mg/kg PO in food or water for 7-10 days. (Morgan 1988), (Kirk 1989), (Greene 1984)
b) Prophylaxis: 30 ml of 9.6% solution in one gallon (3.8 L) of drinking water or (not both) 1.25 grams of 20% powder in food to feed 4 pups daily. Give as sole source of food or water for 7 days prior to shipping. Bitches may be given medicated water (as above) as the sole source of water for 10 days prior to whelping. (USPC 1989)
c) Prophylaxis: 0.075% solution as drinking water (Matz 1995)
a) Treatment: 10 mg/kg PO for 5 days; 5 mg/kg for 21 days for prophylaxis. (Todd, Dipietro, and Guterbock 1986)
Monitoring Parameters -
1) Clinical efficacy
Dosage Forms/Preparations/FDA Approval Status/Withholding Times -
Amprolium 1.25% Medicated Crumbles for Top Dressing in 50 lb bags.; Corid® 1.25% Crumbles (MSD-AgVet); (OTC) Approved for use in calves. Slaughter withdrawal = 24 hours.
Amprolium 9.6% (96 mg/ml) Oral Solution; Corid® 9.6% Oral Solution (MSD-AgVet); (OTC) Approved for use in calves. Slaughter withdrawal = 24 hours
Amprolium 20 % Soluble Powder; Corid® 20% Soluble Powder (MSD-AgVet); (OTC) Approved for use in calves. Slaughter withdrawal = 24 hours
There are many combination products (medicated feeds, feed additives) containing amprolium with other therapeutic agents. These products are approved for chickens (broilers only) and/or turkeys. There are some products containing amprolium alone for use in laying hens.
Human-Approved Products: None
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