Pyridoxine (vitamin B-6) has a number of interesting effects in addition to its actions as a vitamin. High doses (100 milligrams two or three times a day) help relieve nerve compression injuries (like carpal tunnel syndrome), premenstrual syndrome (PMS), and some cases of depression and arthritis. It is often used to treat high homocysteine levels along with folic acid and vitamin B12. It is the only water-soluble vitamin that can be toxic. High doses over time may result in numbness and tingling in the extremeties that may eventually be irreversible. Don't take more than 200 mg a day and take that dose only with caution.