Vitamin B₆ Deficiency

Key Features

• Vitamin B₆ deficiency most commonly occurs as a result of

  • Alcohol use disorder

  • Variety of medications, especially isoniazid, cycloserine, penicillamine, and oral contraceptives

• Although inborn errors of metabolism and other pyridoxine-responsive syndromes are not clearly due to vitamin B₆ deficiency, they commonly respond to high doses of the vitamin

Clinical Findings

• Mouth soreness

• Glossitis

• Cheilosis

• Weakness

• Irritability

• Severe deficiency can result in peripheral neuropathy, anemia, seizures

• May be a correlation between low vitamin B₆ levels and a variety of clinical conditions, including inflammatory diseases and certain cancers

• May be seen concomitantly in patients who have common variable immunodeficiency

Diagnosis

• Serum pyridoxal phosphate levels

  • Normal levels vary per laboratory

  • They are typically > 5.0 ng/mL

Treatment

• Vitamin B₆, 10–20 mg orally once daily

• Patients taking medications that interfere with pyridoxine metabolism (such as isoniazid) may need doses as high as 100 mg/day

• Patients with inborn errors of metabolism require up to 600 mg/day

• Prophylaxis with vitamin B₆ should be routinely given to

  • Patients receiving medications (such as isoniazid) that interfere with pyridoxine metabolism

  • Older patients

  • Patients with alcohol use disorder

• B₆ supplementation has no benefits on cardiovascular outcomes