Tissue damage caused by the intramuscular injection of long-acting penicillin

In order to elucidate whether tissue damage produced on occasion by intramuscular injection of long-acting penicillin is due to accidental intra-arterial injection or vasospasm, two types of experiments were carried out in rabbits. In the first set of experiments, six New Zealand White rabbits were given intra-arterial injections of 0.4 mL of a mixture containing 300,000 U of penicillin G benzathine and 300,000 units of penicillin procaine per milliliter (Bicillin C-R) into the left femoral artery and 0.4 mL of normal saline into the right femoral artery as autocontrol. In a second set of experiments, 0.4 mL of the same penicillin preparation was injected in the space surrounding the left femoral artery in five New Zealand rabbits, and 0.4 mL of normal saline was injected in a similar fashion around the right femoral artery as control. The legs of the rabbits that received the intra-arterial injection of penicillin invariably developed ischemic manifestations. None of the legs of rabbits given intra-arterial injections of normal saline had pathologic manifestations. None of the rabbits that received the periarterial penicillin preparation or normal saline developed abnormalities. These results strongly suggest that the tissue damage produced by penicillin is secondary to the intra-arterial administration of the drug.