Effects of oral treatment with sustained release morphine tablets on hypothalamic-pituitary-adrenal axis

Morphine is suggested to influence immune function by activation of hypothalamic-pituitary-adrenal axis. Thus, we investigated 8 pain patients prior to and during prolonged oral treatment with 30-240 mg of sustained release morphine for plasma concentrations of adrenocorticotropic hormone and serum concentrations of cortisol. Results revealed that pain patients at basal status had elevated cortisol concentrations. Hormone concentrations measured after 1, 4 and 12 weeks of morphine treatment were significantly decreased, not normalized, but at very low values. Since these data, even in the absence of clinical symptoms, might have been indicative for adrenal insufficiency, a corticotropin-releasing hormone test was performed in 2 patients. After injection of 100 micrograms of human corticotropin-releasing hormone. ACTH and cortisol concentrations increased sufficiently. In conclusion, even though low hormonal concentrations were observed in pain patients during morphine treatment, pituitary and adrenal stimulation of the endocrine axis remained intact.