Who knows. I've IMed it in quite large doses and it's been OK, but then again, with IV it delivers all of the drug to the brain in about 15 seconds; this sort of plasma concentration of the drug could have unforseen side effects (a similar thing applies to the opioid dextromoramide, it's OK to give IM for severe pain, but IV use is avoided as by that route it can cause a fatal drop in blood pressure).
So, basically it's probably OK, but I would also first try a small dose (about 5-10 percent of intended full dose), just to make sure that you don't get a overwhelming rssponse, or at least more than you were expecting