[Pharmacokinetic aspects of residues at the injection site]

The disappearance of drug residues from slaughter animals treated by intramuscular route can only be reliably predicted when the dose is rapidly and reproducibly absorbed. In actual practice, this will frequently not be the case. The effects of slow absorption for extinction of residues are illustrated by pharmacokinetic simulation. It is concluded that withdrawal times should not be determined for a drug substance but for any intramuscular formulation of that substance.