Local muscle damage and oily vehicles: a study on local reactions in rabbits after intramuscular injection of neuroleptic drugs in aqueous or oily vehicles.

The local muscle damaging effect of a series of neuroleptics formulated in water or in oily vehicles (Viscoleo, sesame oil, methyl oleate or squalane) has been investigated after intramuscular injection in rabbits. Each drug preparation (2 ml) was administered intramuscularly in the central part of the longissimus dorsi muscle of four rabbits. The rabbits were killed three days after the injection, and the injection site was examined macroscopically. Areas of necrotic muscle tissue were isolated by dissection and weighed. All preparations in aqueous solution caused local muscle damage (large necrotic area) at the injection site. This effect was almost completely neutralized by the Viscoleo vehicle. The sesame oil, methyl oleate and squalane vehicles also neutralized the local damaging effect, but not to the same extent as that of the Viscoleo vehicle.