We studied the effects of the new non-ergot D2-dopamine agonist
roxindol for the treatment of human
prolactinomas.
Roxindol is a non-ergot
drug with additional
5-hydroxytryptamine type 1 A agonist and
serotonin reuptake inhibitory activity. Ten patients with
prolactin-secreting pituitary adenomas received
roxindol three times daily at a dosage of 7.5-30 mg/day for at least 4 weeks according to a prospective protocol. All patients but one had received oral
bromocriptine previously without normalization of
prolactin levels. Serum
prolactin profiles were analyzed once a week during the first month of
therapy and at 4-week intervals thereafter. Mean baseline serum
prolactin was suppressed from 23,000 +/- 13,600 mU/l (range 1500-141,000 mU/l; 20 mU/l = 1 microgram/l) by 37 +/- 11% after 1 week, by 49 +/- 9% after 4 weeks, and by 65 +/- 11% (n = 8) after 24 weeks of treatment. Serum
prolactin was normalized in two patients. A
tumor volume reduction of 20-25% was obtained in two subjects. Compared with previous treatment with oral
bromocriptine the decrease in serum
prolactin was comparable. In contrast, tolerance of
roxindol was superior in five of seven patients with major side effects with
bromocriptine, including three subjects who had discontinued
bromocriptine because of adverse reactions. Four subjects spontaneously reported improvement of psychological and physical performance. One patient had a transient increase of serum
transaminases. Thus, for the first time we could show a suppressive effect of
roxindol on
prolactin secretion in human
prolactinomas. Due to its good tolerance
roxindol may provide a useful alternative to
bromocriptine.