Effects of the opiate agonist loperamide on pituitary-adrenal function in patients with suspected hypercortisolism

In the present work the possible use of loperamide, an opiate agonist, in the dynamic evaluation of patients with suspected hypercortisolism was investigated. The effects of loperamide on plasma ACTH and cortisol levels were evaluated in normal subjects and in 58 patients with suspected Cushing's syndrome. The results were compared to those obtained after the overnight dexamethasone suppression test. In normal subjects plasma ACTH and cortisol levels were significantly (p less than 0.005) suppressed by both loperamide (16 mg po) and dexamethasone (1 mg po). In 17 patients, in whom the diagnosis of Cushing's syndrome was confirmed by subsequent investigations, neither loperamide or dexamethasone inhibited cortisol (from a baseline of 606 +/- 55 nmol/L) to a nadir of 502 +/- 43 nmol/L and 539 +/- 50 nmol/L, respectively) and ACTH concentration (from a basal level of 70.1 +/- 11.8 pg/ml to a nadir of 46.0 +/- 8.6 pg/ml and 54.3 +/- 7.5 pg/ml, respectively). In 34 patients, in whom the suspect of hypercortisolism was ruled out, either loperamide or dexamethasone suppressed the pituitary-adrenal axis: cortisol and ACTH levels significantly fell from 417 +/- 24 nmol/L and 28.3 +/- 3.5 pg/ml to 60 +/- 6 nmol/L and 14.4 +/- 1.4 pg/ml after loperamide and to 26 +/- 4 nmol and 16.4 +/- 1.7 pg/ml after dexamethasone. In 7 patients discordant responses were observed. In 3 patients treated with antiepileptic drugs ACTH and cortisol levels were inhibited by loperamide, but not by dexamethasone.(ABSTRACT TRUNCATED AT 250 WORDS)