Dopamine agonist administration is the primary
therapy for
macroprolactinomas, but
bromocriptine is the only agent approved in the United States. Its use is limited by a high incidence of side effects, a short duration of action, and a lack of effectiveness in some patients.
Cabergoline is a long-acting
dopamine agonist specific for the D2 receptor that is more effective and better tolerated than
bromocriptine in women with microadenomas or idiopathic
hyperprolactinemia. However, experience with
cabergoline in the treatment of patients with macroadenomas is limited. We report the first study of chronic administration of
cabergoline conducted exclusively in patients with
macroprolactinomas. Fifteen patients (8 women, 7 men) ages 18-76 yr were studied in an open-label 48-week dose escalation trial of
cabergoline administered once per week. Eleven patients had received prior
therapy with other
dopamine agonists. Mean
prolactin (PRL) levels decreased by 93.6%, and normal levels were attained in 73% of patients at doses of 0.5-3.0 mg per week. Three of five patients who had failed to normalize PRL on prior
dopamine agonists achieved normal levels. Gonadal function was restored in all hypogonadal men and in 75% of premenopausal women with
amenorrhea.
Tumor size decreased in 11 of the 15 patients. Side effects were minimal. Of the 5 patients who had experienced side effects in prior
dopamine agonists, 4 had none on
cabergoline, and the fifth had milder symptoms. During two further years of follow up, the improvement in PRL levels, gonadal function, and
tumor size has persisted during
cabergoline administration, and three patients have experienced a further decline in PRL and/or
tumor size. This study demonstrates the effectiveness and minimal side effects of once-weekly
cabergoline for treatment of
macroprolactinomas.