Side Effects Of Pyridoxine

Once widely prescribed for nausea in pregnancy, pyridoxine fell out of favor in the 1970s after lawsuits alleged an association with birth defects. The relationship between the drug containing pyridoxine and birth defects proved false after multiple studies, reports "American Family Physician" in a July 1, 2003, review article, but the use of pyridoxine for this purpose never quite recovered.

Supplements do not require a prescription, and many other uses for pyridoxine, a form of vitamin B6, have surfaced. Pyridoxine elicits almost no side effects at therapeutic, doses but if you take the vitamin at higher than recommended levels, severe and significant side effects can occur.

Numbness and Tingling

Research does not consistently support a benefit of high doses of pyridoxine for conditions such as premenstrual syndrome or carpal tunnel syndrome, but many people continue to take them for these disorders.

A toxic sensory neuropathy related to overdose of pyridoxine continues to be reported, though, explains the medical text, "Neurology in Clinical Practice." Pyridoxine plays an important role in nerve conduction. Toxicity likely results from over-stimulation of the nerves by too much of the vitamin, which then causes degeneration of the nerve endings. Taking as little as 300 mg per day for over a year may result in sensory deficits. Numbness and tingling of the extremities, sometimes associated with severe pain, represent the most common findings of this type of neuropathy.

Coordination and Walking Difficulty

If you take high doses of pyridoxine -- over 1,000 mg per day -- for more than three months, you risk development of problems with walking. Neurologic deficits advance from a mild neuropathy, with numbness and tingling, to the inability to sense the position of your feet. Walking becomes labored and difficult and eventually impossible, according to "Neurology in Clinical Practice." Coordination difficulty, due to sensory deficits, manifests in the arms and fingers as well, resulting in difficulty with daily activities.

Luckily, most people, even those with disabling neurologic problems due to pyridoxine, improve after about six months once the supplementation of vitamin B6 stops, says "Neurology Clinics" in its February 2007 issue.

Fatigue and Non-Specific Symptoms

Because of the reports of toxic neuropathies, the Institute of Medicine, in 1998, established the value of 100 mgs per day as an upper tolerable limit of vitamin B6 for most adults, reports the Office of Dietary Supplements. Still, people continue to self-prescribe higher doses of pyridoxine for various conditions despite a lack of consistent evidence of any benefit of high doses for these conditions.

Before the onset of neurologic signs, non-specific symptoms may also indicate that you take an excessive dose of pyridoxine. Fatigue presents commonly as a sign of deficiencies and overdoses of many vitamins, including pyridoxine. MayoClinic.com states that muscle cramps, vomiting, loss of appetite and headaches all might provide clues to impending toxicity. Non-specific symptoms may not seem obvious, since all of these findings could result from other medications or disorders.