Drug--vitamin B6 interaction.

In conclusion, there are several drug types that can interfere with vitamin B6 metabolism. In most cases, the interaction involves a complex formation between the drug (or a derivative) and the reactive coenzyme PLP, resulting in a Schiff base. Such an interaction leads to an inactivation of PLP (and also of the drug). Other types of interaction involve (a) stimulation of vitamin B6-dependent pathways and (b) competition with PLP for the binding site on the enzyme. Examples of the above are the steroid hormones (oral contraceptives). In most instances, overt symptoms of vitamin B6 deficiency due to chronic ingestion of these drugs are observed, and neurological problems seem to be rather frequent. Because of the reactive nature of the coenzyme PLP and the ease with which it can interact with drugs, sub-clinical (marginal) vitamin B6 deficiency should be suspected in the absence of overt clinical signs. Once the vitamin B6 problem has been identified, the condition can usually be treated by judicious use of large doses of vitamin B6 without compromising the clinical efficacy of the drug.