EFFECT OF LOW-DOSE DOPAMINE ON SERUM CONCENTRATIONS OF PROLACTIN IN CRITICALLY ILL PATIENTS

Dopamine is a naturally occurring catecholamine with actions in the ce ntral nervous system and endocrine systems, including inhibition of pr olactin release from the pituitary gland. Prolactin secretion has been shown to be increased in response to physiological stress, while hypo prolactinaemia is associated with a reduction in the cellular immune r esponse. We have investigated the effects of low-dose infusion of dopa mine 2.5 mu g kg(-1) min(-1) on serum concentrations of prolactin in c ritically ill patients. Six hours after commencing the dopamine infusi on, mean serum prolactin concentration had decreased from 746.95 (norm al range 84-488 mu. litre(-1)). This represented a mean reduction of 7 9.2%, with 35% of patients exhibiting a subnormal concentration while receiving dopamine. This reduction was reversed after cessation of dop amine and reproducible on re-institution. This suppression of the rele ase of dopamine may be a detrimental side effect of low-dose dopamine infusion in critically ill patients.