Long-lasting suppression of prolactin secretion and rapid shrinkage of prolactinomas after a long-acting, injectable form of bromocriptine.

Since Corenblum reported in 1975 the first documented reduction of tumor size in two patients with macroprolactinoma, evidence has accumulated that bromocriptine causes shrinkage of PRL-secreting adenomas in most patients. Recently a long-acting form of bromocriptine (bromocriptine LA) was developed. A single dose of 50 mg i.m. decreases basal and sleep-related PRL secretion in normal subjects for 28 days. We treated 13 patients (8 women, 5 men) with PRL secreting tumors (5 macroadenomas and 8 microadenomas) with a single dose (50 mg) of bromocriptine LA. In the 5 patients with macroprolactinomas plasma PRL levels decreased markedly within 12 hours, reaching normal levels in only one patient. In all patients the suppression of PRL secretion lasted at least 28 days and the tumor size was reduced by 20% to 59% within 21 days after the injection. Visual fields improved in all 3 patients with abnormal vision prior to the injection. In one patient with bitemporal hemianopsia an almost normalization of the visual field was noted 24 hours after bromocriptine LA administration. In 7/8 patients with microprolactinomas plasma PRL levels decreased to within the normal range within 12 hours after the administration of bromocriptine LA. The normalization of PRL secretion lasted for at least 28 days. Menses resumed in all 6 women 7 to 41 days after the injection, galactorrhea disappeared in all 4 patients, and libido and potency become normal in both men with microprolactinomas. Patients treated with bromocriptine LA reported only short-lasting (1 hour - 2 days) mild or moderate adverse effects, consisting of dizziness (4 patients) and nausea (4 patients). Long-acting bromocriptine should be considered as the initial management for patients with PRL-secreting tumors. The use of bromocriptine LA could also overcome the compliance problems that occur in many patients soon after the initiation of oral bromocriptine therapy.