Alcohol impairs intestinal absorption of vitamin B2.
Phenothiazines, Tricyclic Antidepressants: These drugs may inhibit the conversion of vitamin B2 to the active coenzyme form. Requirements for vitamin B2 may be increased in patients receiving these drugs.
Probenecid: The extent of gastrointestinal absorption of vitamin B2 is decreased when it is used concomitantly with probenecid.
Vitamin B2 is usually well tolerated and nontoxic. Because of its fluorescent yellow color, vitamin B2 may cause yellow discoloration of urine. Diarrhea and gastrointestinal upset have been reported with higher doses.
In preventing vitamin deficiencies, adequate dietary intake is preferred over supplementation whenever possible. Vitamin B
2 is found in milk, meat, eggs, nuts, enriched flour and green vegetables. For a listing of food sources and recommended intake of vitamin B
2 and other nutrients, see Nutrient Requirements in the Clin-Info section.
Vitamin B2 is usually given orally. It may also be given by im injection or iv infusion as a component of multivitamin injections. It is recommended that vitamin B2 deficiency be treated with multivitamin preparations since it is often associated with other vitamin deficiencies.
The usual oral dose in the treatment of deficiency is 5 to 30 mg daily in divided doses for adults and 3 to 10 mg daily in divided doses for children. Ocular and dermatologic symptoms should improve after several days. Reticulocyte count should begin to increase within a few days in patients with normocytic or normochromic anemia.
The dose that has been used in migraine prophylaxis is 400 mg orally daily
