The World Health Organization recently reviewed veterinary drug residues in food and concluded that many drugs used to "aid animal production" (read: drug the animals before slaughter) may be harmful to your health.
Some of the drugs included carazolol, a beta blocker given to prevent stress induced sudden death in pigs, which could cause problems in asthmatics. Other drugs were antimicrobials and tranquillizers.
WHO recommended that attention to improvements in pre slaughter animal handling should diminish the need for drug treatment. It also plans to study the effects of drugs on the offspring of pregnant women, and non veterinary drugs given simply to boost muscle growth or weight.