Effectiveness of a long-acting injectable form of bromocriptine in patients with prolactin and growth hormone secreting macroadenomas.

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.