The attenuated HPA axis negative feedback (consequent on attenuated check details cortisol synthesis) after repeated metyrapone administration results in increased levels of ACTH, DHEA and 11-deoxycortisol levels, though with near normal plasma levels of cortisol [Jahn et al. 2004; Otte et al. 2007]. Metyrapone also inhibits 11β-HSD1

and the subsequent unopposed inactivation of cortisol by 11β-HSD2 results in an increase in the plasma cortisone:cortisol plasma ratio. Metyrapone also inhibits the production of aldosterone. Figure 1. Steroid synthesis pathway. Metyrapone acts by blocking the conversion Inhibitors,research,lifescience,medical of 11-deoxycortisol to cortisol by P450c11 (11β hydroxylase). In humans, metyrapone is rapidly absorbed following oral administration. Blood levels peak 1 h after ingestion [eMC, 2010]. It has a half life of 20–26 min. Metyrapone’s main active metabolite –metyrapol – has a half life twice that of the parent compound. Metyrapone is excreted Inhibitors,research,lifescience,medical in the urine as metyrapone or as metyrapol [eMC, 2010]. Metyrapone is used in clinical practise as an aid for the differential diagnosis of ACTH-dependent

Cushing’s syndrome and in the medical management of Cushing’s syndrome and aldosterone-induced oedema. Metyrapone is administered in doses varying from 250 mg to 6 g per day depending on the indication [Joint Formulary Inhibitors,research,lifescience,medical Committee, 2011]. Metyrapone is well tolerated. In a blinded study on patients with TRD, in which metyrapone was used alongside serotonergic antidepressants, only headaches and nausea were reported more frequently by participants in the metyrapone group compared with the placebo group [Jahn Inhibitors,research,lifescience,medical et al. 2004]. Other undesirable effects of metyrapone use include occasional vomiting, dizziness, sedation, hypotension and rarely hypoadrenalism, hirsuitism, allergic skin reactions and abdominal pain [eMC, 2010]. Metyrapone and treatment of treatment-resistant depression There is limited evidence for the use of metyrapone in the treatment of depressive illness. Most of the evidence comes from three sources:

preclinical Inhibitors,research,lifescience,medical studies, where the effect of metyrapone on animal models of depression is examined; studies on patients with Cushing’s syndrome and secondary depressive illness; and clinical studies of the effect of metyrapone in patients with depression. The data from preclinical studies are based on studies of the effect of metyrapone treatment medroxyprogesterone on the behaviour of rat models of depression or on the neurochemistry of the brain of rats. Healy and colleagues compared the effect of metyrapone with that of desipramine and placebo treatment in two rodent models of depression: the olfactory bulbectomized (OB) rat and the forced swim test (FST) [Healy et al. 1999]. In the OB rats, 14-day treatment with metyrapone (50 mg/kg) or desipramine attenuated OB-related hyperactivity.