Intra- vs intermuscular injections in swine

In order to determine the exact localization (intra- vs intermuscular) in which a drug is injected when administered by a so-called intramuscular injection technique, a radiopaque test article (2 ml) was injected into the cervical musculature (2 sites), the loins and the gluteal mass in anaesthesized pigs. Immediately after this, the pigs were euthanized and deep-frozen. Then they were cut into slices, which were X-rayed to determine the exact localization of the test material. Semi-quantitative scores were given to each injection site according to the amount of test article found in or out of muscle mass and also to the absence or the presence of test article subcutaneously. The loins area obtained the highest score for intramuscular location, but in this site, injections were almost always followed by a flowing back of the test article to the subcutaneous' area. It was shown that an injection in the neck perpendicular to the skin surface just behind the base of the ear was the most appropriate site for intramuscular injection in pigs.