The rapid diagnosis of sensitivity or resistance to dopamine agonists with depot bromocriptine

Some patients with hyperprolactinaemia are unable to tolerate even low doses of oral bromocriptine. In such cases, it is difficult to predict whether serum prolactin might be normalized if higher doses could be tolerated, or whether true resistance to bromocriptine is present. We have investigated 8 such patients who were subjected to a dopamine infusion (4 micrograms/kg per min for 4 h), followed by an injection of 50 mg of depot bromocriptine on a separate occasion. Serum prolactin was normalized in 4 patients during dopamine, and in 6 patients 12-48 h following depot bromocriptine. The 2 patients who failed to respond to depot bromocriptine also failed to respond to high oral doses of bromocriptine, while the remaining 6 patients were successfully transferred to oral bromocriptine without adverse reactions after the depot preparation was administered, and with a normalization of serum prolactin. It is concluded that depot bromocriptine may represent a better predictor of true unresponsiveness to dopamine agonist therapy than a dopamine infusion, and may also allow for initiation onto oral therapy of previously intolerant patients.