Phenylbutazone in the food chain – now possibly Pork meat?

Phenylbutozone (PZB) has been found in 4% of beef tested so far in France. The drug, originally approved for rheumatoid arthritis and gout in the 1940s/1950s is now banned from use in human medicines in the US and UK due to tests indicating kidney and liver cancer in humans. It is thought that PZB subtly alters the structure of chromosomes in bone marrow; therapeutic doses of several hundred miligrams cause blood disorders and internal organ damage along with severe toxic reactions in a minority of cases.

Formation of the drug is obtained by condensing diethyl n-butylmalonate with hydrazobenzene; it is used primarily as an analgesic in horses and dogs to relieve suffering from sprains, arthritis and similar musculoskeletal tissue. ‘Bute‘, as it is described in equestrian circles, is in common use in horses (with 2 to 5 per cent of abbatoir samples of slaughtered horsemeat testing positive for PZB in the past five years). However, horse meat being found in supermarkets in Europe labeled as beef is now revealing instances of phenylbutazone.

There is however a real and present danger to humans, as PZB has no clinically defined ‘safe level’ for human consumption.

It has been posited that PZB may have carcinogenic effects in humans after laboratory tests found rats to be susceptible. Worryingly, the site AmericanHorseMeat reports,

…The U.S. Department of Agriculture’s (USDA’s) Food Safety Inspection Service has reported phenylbutazone residues in culled cattle presented for slaughter for human food throughout the United States in the past 2 calendar years. This evidence indicates that the extralabel use of phenylbutazone in female dairy cattle 20 months of age or older will likely result in the presence, at slaughter, of residues that are toxic to humans, including being carcinogenic, at levels that have not been shown to be safe.1

The USDA’s report revealed further systematic abuse of the HAACP system used by abbatoirs in the USA, with repeated PZB residue contamination amongst more serious problems like salmonella. And in October 2012, an article in Horseback Magazine2 included a letter from a group of organisations opposed to horse slaughter, referencing a European Commission report evaluating the operation of controls over the production of horsemeat for export to the European Union. Residue monitoring plans for imported horse meat “must be submitted [by abbatoirs] in accordance with Council Directive 96/23/EC, in particular Article 29,” only then being eligible for import into the EU.

Systematic failures lead to tainted food chain

Aside from Equine Identity Documents, the evident systematic failure of abbatoirs’ HAACP self-assessment and lax controls on animals already slaughtered inside the EU (and not subjected to the same strictures of import regulations) shows just how problematic this whole area can be. Indeed, in late 2011, Horseback Magazine also highlighted3 that,

“[…] Phenylbutazone metabolises into oxyphenylbutazone (also linked to blood dyscrasias such as aplastic anemia) which persists much longer [in the bloodstream than PZB]”, and that phenylbutazone can be[…] taken up in injured tissue, where it may later be released back into the bloodstream.”

The article continues,

A recent paper issued by Irish Veterinarians further cement the dangers of bute and the disciplinary action to veterinarians for sending an animal to slaughter that has been administered bute. The paper states, “The difficulty with phenylbutazone is that it, or its metabolite, can cause aplastic anemia in children. If a child were to consume an animal-based product containing even the minutest amount of bute or its metabolite [oxyphenylbutazone] then the child may develop aplastic anemia.”

In addition, the paper warns, “It is a statement of fact that if the European Commission on its audit of this country find evidence of bute use in animals not excluded from the food chain, then the product will immediately lose its license Europe-wide.

If samples prove positive for phenylbutazone or its metabolite in equine meat of Irish origin, it will be traced back, and the prescribing veterinary practitioner will be in the firing line of prosecution.”

Only a week ago Food Production Daily exposed the risk of tainted horse meat in an article titled Tainted US horse meat puts world consumers at risk.

“US horses are not raised as meat animals”, said EWA spokesperson Vicki Tobin, “It is just that simple. If we want to keep sending our horses to slaughter, we will have to give up most of the effective medications we currently enjoy.”

And now, pork?

A further danger, which we believe is being reported first by this web, that Phenylbutazone may also be entering the food chain through Pork:

The web site “Asian Pharma“, run by Asian Consumables India PTY Ltd in Tamil Nadu India, clearly shows pigs being administered with 1% PZB. The web site appears to direct its sales to countries including the United Kingdom and purports to be certificated by the Pharmaceuticals Export Promotions Council. The need for the use of bute in pigs is unknown, but livestock with the potential of entering the human food chain are banned from being administered the medicine in the EU.

The web site mentioned above (screen shot below) can be viewed at

Asia Pharam 4


  1., []
  2. Horseback Magazine, []
  3. Horseback: “EWA Strongly Rebukes Letter Criticizing Landmark Study While Ignoring Food Trade Publication Tainted Meat Warning”; []
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