Also, from what I understand, the IM penicillin shot with the procaine should be refrigerated before use. If it was on a trip, it may have been too warm and therefore the procaine could have entered the bloodstream even if the needle didn't hit the vein. The penicillin wasn't the problem, the procaine (and possibly the method of administration) was. Don't throw the baby out with the bathwater, please. Penicillin is a very useful drug.