Local Toxicity and Pharmacokinetics After Intramuscular or Intralipomatous Injection of Different Drugs in Pigs
The question was posed by Cockshott et al. (1982) whether it matters if drugs are given as intramuscular (i.m.) or intralipomatous (i.l.) injection. The thickness of gluteal fat and CT scans of pelvis suggested that the majority of injections intended to be i.m. in fact were delivered i.l.
Local toxicity and pharmacokinetics were studied after i.m. or i.l. injection of different drugs in pigs, which have a subcutaneous layer of fat comparable to that of man. The pigs were killed 1, 3, 7 or 14 days after injection of antibiotics, vitamins or neuroleptics. The tissues at the injection site were examined macroscopically and microscopically. In another series of experiments an aqueous or two different oily preparations of the neuroleptic drug cis(Z)-clopenthixol were given i.m. or i.l. to pigs and a series of blood samples were taken for drug level determination.
The tissue examinations showed that all drugs causing local muscle damage after i.m. injection caused considerably less extensive damage with a faster regeneration after i.l. injection. Only one drug which did not cause muscle damage after i.m. injection, caused some, but slight, irritation after i.l. injection. The pharmacokinetic study showed that there was no difference between plasma concentration time curves after i.m. or i.l. injection.
These findings suggest that i.l. injection of the damaging drugs is better than i.m. injection since i.l. injection causes less local toxicity and the pharmacokinetics are identical. However, further studies are required to substantiate whether this is a general finding.
Key wordsInjection Intramuscular Intralipomatous Local toxicity Pharmacokinetics Pigs
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