Dietary deficiency is very rare. Some drugs, for example isoniazid, hydralazine and penicillamine can interact with pyridoxal phosphate, that producing B 6 deficiency. The polyneuropathy occurring after isoniazid generally responds to vitamin B6. Sideroblastic anaemia rarely responds to vitamin B6. A polyneuropathy has occurred after high doses (>200 mg) given over many months. Vitamin B 6 is used for premenstrual tension: a each day dose of 10 mg must not be exceeded.