A feed additive used to help prevent coccidiosis in poultry will be suspended from sale in Canada next month, reports Alberta Farm Express.

Pfizer Animal Health's Canadian arm and Winnipeg veterinary drug distributor Dominion Veterinary Laboratories will voluntarily suspend sales of roxarsone, as sold in the products 3-Nitro-20 and Super Nitro-12, effective 8 August.

Pfizer's Alpharma subsidiary in the US planned to take much the same action starting early this month in response to a request from the US Food and Drug Administration (FDA), citing its own study of the drug.

According to a notice from Health Canada's Veterinary Drugs Directorate, the FDA study had found inorganic arsenic, a known carcinogen, at higher levels in the livers of chickens treated with the nitro drugs, compared with untreated chickens.

Health Canada said it had reviewed the FDA study and agrees with its conclusion that the levels of inorganic arsenic involved were 'very low' and posed no immediate health risk to people eating meat from birds treated with the drugs.

Rather, Health Canada said, the suspension of sales is "a precautionary measure to remove any avoidable exposure to very low levels of inorganic arsenic in chickens treated with roxarsone".

While Pfizer Animal Health's Canadian arm had no official comment on the planned suspension, New York-based Pfizer said in a release on 8 June that the "extremely low" levels found in the FDA study were "equivalent to the amount of inorganic arsenic found in an eight-ounce glass of drinking water".

Pfizer cited the FDA study in saying that "even in the context of this recent data, there is no need for people to alter their consumption of chicken. Low levels of inorganic arsenic occur naturally in a wide range of commonly eaten foods that are considered safe to eat, including meats, fish, vegetables, grains and legumes".

The US company said it viewed the suspension there as "prudent in light of the (FDA's) request that Pfizer assist in removing an avoidable exposure to very low levels of inorganic arsenic".

In the US, 3-Nitro had been allowed for use in prevention of coccidiosis, a common infection in poultry, and to improve gain and feed efficiency in poultry and hogs. Its use in hogs in the US was "negligible", Pfizer said.

According to Alberta Farm Express, Pfizer said it would continue working with the FDA to "examine further relevant scientific data regarding the use of this product in animals, and would continue its own review of the results of the FDA study.