[Vitamin B12, an analgesic vitamin? Critical examination of the literature].

Since 1950 it would seem that in some countries vitamin B12 has been regarded as a painkilling vitamin. Only one of the 94 published clinical trials fails to point to this conclusion, but none of these trials meets current methodological requirements for investigation of an analgesic. The hypothesis that vitamin B12 possesses painkilling properties must therefore be questioned, especially as no anti-nociceptive effect is reported in animal experiments.