THE EFFECTS OF ANTICONVULSANT DRUGS ON ADRENAL-FUNCTION

Since the adrenal cortex and medulla are intimately interrelated, the effects of anticonvulsant drugs may affect both of these hormonal syst ems. Anticonvulsants are commonly used long-term for the treatment of epilepsy, chronic pain syndromes and affective disorders, In patients where adrenal function needs to be evaluated, the clinician should be aware of the potential interactions between anticonvulsant medication and the hypothalamo-pituitary-adrenal axis. Carbamazepine, phenytoin a nd phenobarbitone induce the liver P450 cytochrome enzyme system and s timulate steroid clearance. Therefore, patients investigated for Gushi ng's syndrome may show a falsely positive dexamethasone suppression te st, and patients with adrenal insufficiency on steroid replacement may require increased doses of steroids; furthermore, increased corticost eroid-binding-globulin levels are also associated with chronic anticon vulsant administration. In addition, concomitant treatment with benzod iazepines, probably acting via the GABA pathway, can also alter the AC TH/cortisol response to stressful stimuli. Direct and indirect evidenc e suggest that benzodiazepines, acetazolamide and magnesium sulphate c an also interfere with the renin-angiotensin-aldosterone system. Final ly, to our knowledge, no systemic data are yet available in the human on the effect of antiepileptics on the function of the adrenal medulla and/or catecholamine metabolism however, as the adrenal medulla recei ves part of its blood supply from the cortex, it is possible that alte rations of cortical hormonal composition might affect adrenal medulla function overall.