A comparison of the effects of vitamin B12 and aspirin in three experimental pain models in rats and mice.

The effects of vitamin B12 are compared to those of aspirin and 0.9% saline in three different experimental pain models in rats and mice; an electric shock test, the hot-plate test, and the phenylbenzoquinone writhing test. Neither cyanocobalamin nor hydroxocobalamin showed any antinociceptive activity in any of the three tests at any of the doses used, whether the drug was administered as a single injection or as a series of daily injections lasting 7 days. These results run counter to those of clinical trials in man, though close scrutiny of the experimental procedures used in these trials often reveals a lack of rigor which casts doubts on their validity. This consideration, together with the negative findings reported here, suggests that the clinical use of vitamin B12 as an analgesic may be inappropriate.