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Dopamine agonists are the drugs of choice for prolactinomas
Dopamine agonists (DA) are the first-line treatment for the majority of patients with prolactinoma or nontumoral hyperprolactinemia. The main DA drugs used in clinical practice are bromocriptine, cabergoline and, to a lesser extent, quinagolide. Bromocriptine, an ergot-derived compound, was the first DA to be introduced in the 1970s for the treatment of hyperprolactinemia. Bromocriptine binds and stimulates dopamine D 2 -receptors in normal and tumoral lactotroph cells, leading to the inhibition of prolactin (PRL) synthesis and secretion. However, approximately 30% of patients with prolactinomas do not tolerate this drug at therapeutic doses or are resistant. Cabergoline is another ergot derivative with high affinity and specificity for the dopamine D 2 -receptors. It is generally the agent of choice because it has a longer duration of action, is better tolerated and is more effective in normalizing PRL and tumor shrinkage [1,2]. Quinagolide, a nonergot DA drug, which is not available in the USA, has specific affinity to the dopamine D 2 -receptor, with an efficacy profile between that of cabergoline and bromocriptine. In patients with hyperprolactinemia, including prolactinomas, normalization of PRL levels is usually obtained with doses of cabergoline ranging between 0.5 and 2 mg/week. Higher doses have been used in cases with important resistance to DA. Approximately 20% of patients with macroprolactinomas and 10% with microprolactinomas required a cabergoline dose of more than 2 mg/week (up to 11 mg/week) to achieve PRL-level normalization (85--95% of cases) [3].
All of the DAs have side effects, such as transient gastrointestinal disorders, dizziness or sleepiness. However, except for a recent case report [4], long-term adverse effects have not been described in patients with prolactinomas.
Valvulopathy is a safety concern of cabergoline therapy in Parkinson''s disease
Retroperitoneal and pleuropulmonary fibrosis have been described in some patients with Parkinson''s disease, generally treated with doses of cabergoline up to 3--6 mg/day. The occurrence of these rare cases has not substantially affected the routine clinical use of these drugs. However, recent reports of fibrotic cardiac valve abnormalities in patients with Parkinson''s disease treated with high doses of cabergoline and pergolide have raised concerns about the safety of chronic DA therapy [5,6]. In a meta-analysis conducted by Simonis et al. , 34% of...