If you are currently being treated with any of the following medications, you should not use vitamin B6 supplements without first talking to your healthcare provider.

Antibiotics, Tetracycline
Vitamin B6 should not be taken at the same time as the antibiotic tetracycline because it interferes with the absorption and effectiveness of this medication. Vitamin B6 either alone or in combination with other B vitamins should be taken at different times from tetracycline. (All vitamin B complex supplements act in this way and should therefore be taken at different times from tetracycline.)

Antidepressant Medications, Tricyclic
Taking vitamin B6 supplements may improve the effectiveness of certain tricyclic antidepressants such as nortriptyline, especially in elderly individuals. Other tricyclic antidepressants include desipramine and imipramine.

On the other hand, another class of antidepressants called monoamine oxidase inhibitors (MAOIs) may reduce blood levels of vitamin B6. Examples of MAOIs include phenelzine and tranylcypromine.

Antipsychotic Medications
Preliminary evidence suggest that pyridoxine may prove useful in treating tardive dyskinesia, a common but frustrating side effect from medications used to treat schizophrenia. Tardive dyskinesia is marked by involuntary movements of the mouth and tongue. More research is needed to know if vitamin B6 can help prevent or treat this side effect.

Tuberculosis Medications
Anti-tuberculosis medications such as isoniazid (INH) and cycloserine (used for resistant forms of tuberculosis) reduce the levels of vitamin B6 in the blood.

Birth control medications
Birth control medications may reduce blood levels of vitamin B6.

Chemotherapy
Vitamin B6 may reduce certain side effects of 5-fluorouracil and doxorubicin, two agents used to treat cancer without reducing the effectiveness of the chemotherapy.

Erythropoietin
Erythropoietin therapy used for severe anemia may decrease vitamin B6 levels in red blood cells. Therefore, vitamin B6 supplementation may be necessary during erythropoietin therapy.

Hydralazine
Vitamin B6 decreases the effectiveness of hydralazine, a medication used to treat high blood pressure.

Levodopa
Vitamin B6 reduces the effectiveness of levodopa, a medication used to treat Parkinson's disease.

Methotrexate
People with rheumatoid arthritis taking this medication often have low levels of vitamin B6.

Penicillamine
Penicillamine, a medication used in the treatment of rheumatoid arthritis and Wilson's disease (excessive amounts of copper in the body that can lead to liver damage) may decrease levels of vitamin B6 in the body.

Phenytoin
Vitamin B6 reduces the effectiveness of phenytoin, a medication used to treat seizures.

Theophylline
Long-term treatment with theophylline for asthma may reduce blood levels of vitamin B6.