The prolactin-lowering efficacy of cabergoline tablets was demonstrated in 647 females with hyperprolactinemic disorders (including 55% microprolactinomas, 7% macroprolactinomas, 3% empty sella syndromes, and 3% idiopathic) in two randomized, double-blind, studies: one 4-week placebo-controlled dose-response study with an 12-month open-label extension (Study 1) and one 8-week active comparator study comparing cabergoline tablets and bromocriptine with 16-week open extension (Study 2).
Study 1: 4-Week Placebo-Controlled Dose-Response Study
Study 1 enrolled 188 non-pregnant, hyperprolactinemic females (these patients had a prolactin level >20 ng/ml (the upper normal reference limit)) with the following hyperprolactinemic etiologies: macroprolactinoma (60%, n=113), idiopathic (36%, n=67) and another etiology (4%, n= 8). Patients had a mean age of 32 years (range, 16-46 years of age), 99% were White (n=186), 0.5% were Asian (n=1) and 0.5% were another race (n=1). Patients were randomized one of the following five oral treatments given twice weekly for four weeks (for the cabergoline tablets groups, the first week the cabergoline tablets dosage was lower to reduce the risk of hypotensive reactions):
- Group 1: placebo twice weekly (n=20)
- Group 2: 0.0625 mg of cabergoline tablets twice weekly for the first week followed by 0.125 mg twice weekly for the next three weeks (n=42)-this dosage is not recommended because this dosage was not effective and results from this group are not presented below [see Dosage and Administration (2.2)],
- Group 3: 0.25 mg of cabergoline tablets twice weekly for the first week followed 0.5 mg twice weekly for the next three weeks (n=42),
- Group 4: 0.375 mg of cabergoline tablets twice weekly for the first week followed 0.75 mg twice weekly for the next three weeks (n=42), and
- Group 5: 0.5 mg of cabergoline tablets twice weekly for the first week followed 1 mg twice weekly for the next three weeks 0.75 mg, (n=42).
In Study 1, the endpoint was the percentage of patients who achieved a normal serum prolactin level (<20 ng/dL) at the end of the 4-week treatment period. At 4-weeks, 0%, 76%, 74% and 95% of patients in the placebo group (group 1), group 3, group 4, and group 5, achieved normal serum prolactin levels, respectively (p <0.0001 across all the cabergoline tablets groups vs. placebo).
Study 2: 8-Week Active Comparator Study
Study 2 was an 8-week, randomized, double-blind active-control study that compared cabergoline tablets (n=223) with bromocriptine (n=236) for the treatment of hyperprolactinemic amenorrhea. In this study, patients had a mean age of 31 years (range 16 – 46 years of age). Patients were randomized to oral cabergoline tablets 0.5 mg twice weekly or oral bromocriptine 2.5 mg twice daily for eight weeks (there was an attrition rate respectively of 46% and 43%, in the cabergoline tablets and bromocriptine groups, respectively). Endpoints included percentage of patients who achieved the following at 8 weeks:
- A normal serum prolactin level (<20 ng/dL)
- Restoration of menses
- Disappearance of galactorrhea
In Study 2, at 8 weeks, cabergoline tablets-treated and bromocriptine-treated patients had a normal serum prolactin level (77% and 59%, respectively), restoration of menses (77% and 70% respectively), and disappearance of galactorrhea, 73% and 56%, respectively).
The durability of the efficacy of cabergoline tablets beyond 24 months of therapy has not been established.