Objective: With the development of new long-acting depot preparations of bromocriptine (bromocriptine LAR), we investigated the effectiveness of intramuscular injections of long-acting bromocriptine in patients with prolactin and GH secreting macroadenomas.
Study design and patients: Fourteen patients with PRL secreting (8 patients) and GH secreting (6 patients) macroadenomas were treated with monthly intramuscular injections of a long-acting and repeatable form of bromocriptine for 3-6 months. A 50-mg monthly dose was administered in the majority of patients with PRL secreting macroadenomas. A 100-mg monthly dose was administered in all patients with GH secreting macroadenomas.
Measurements: Plasma PRL and/or GH levels were measured 6 and 12 hours after the first injection and then on days 1, 2, 14 and 28 after each injection, up to a maximum period of 6 months. Patients were hospitalized for 48 hours after each injection and were specifically questioned with respect to side-effects. Pituitary imaging with MRI or CT scans was performed in all patients before commencing treatment and was subsequently repeated in 5/8 patients with macroprolactinomas and 5/6 patients with GH secreting macroadenomas after the completion of a 6-month course of treatment.
Results: In all patients with macroprolactinomas, serum PRL levels decreased significantly after their first 50-mg injection with nadir levels obtained by 24-48 hours post injection (12815 +/- 8704 vs 1480 +/- 1859 mU/l; mean +/- SD, P < 0.01). At their latest follow-up, on a 50-mg monthly dose, 4 patients developed normoprolactinaemia (PRL levels < 360 mU/l) while two patients demonstrated a significant reduction in serum PRL levels (70 and 87% or pretreatment values). In two patients, although a substantial decrement of serum PRL levels was achieved 12-24 hours post injection, serum PRL levels increased to pretreatment values by day 14 post injection. Both patients received a higher (100 mg) monthly dose which was partially effective in one patient. In two patients with GH secreting macroadenomas, a sustained decrease of elevated GH levels was observed; in two patients, while a substantial reduction of the elevated serum GH levels was achieved 12-24 hours after the first and subsequent injections, serum GH levels increased to pretreatment values by day 14 post injection; in two patients there was no effect on the elevated serum GH levels. Significant tumour shrinkage (24-50%) was observed in 5/5 patients with PRL secreting macroadenomas assessed at completion of a 6-month course of treatment. Significant tumour shrinkage was also documented in 2/5 acromegalics tested (29 and 46% respectively).
Conclusion: It is concluded that bromocriptine LAR is an effective treatment in the majority of patients with macroprolactinomas; it is also partially effective in some patients with GH secreting macroadenomas.