Acromegaly dopamine agonists

Dopamine agonists are also used for the treatment of acromegaly, but although they are much cheaper than somatostatin analogues, they are also less effective, and rarely normalize serum GH concentrations. 

Mechanism of Action A dopamine agonist that directly stimulates dopamine receptors in the corpus striatum and inhibits prolactin secretion. Also suppresses secretion of growth hormone. Therapeutic Effect Improves symptoms of parkinsonism, suppresses galactorrhea, and reduces serum growth hormone concentrations in acromegaly. 

Dopamine agonists suppress prolactin release very effectively in patients with hyperprolactinemia. GH release is reduced in patients with acromegaly, although not as effectively. Cabergoline and bromocriptine are also used in Parkinson s disease to improve motor function and reduce levodopa requirements (see Chapter 28). Newer, nonergot D2 agonists... 

A dopamine agonist alone or in combination with pituitary surgery, radiation therapy, or octreotide administration can be used to treat acromegaly. The doses required are higher than those used to treat hyperprolactinemia. For example, patients with acromegaly require 20-30 mg/d of bromocriptine and seldom respond adequately to bromocriptine alone unless the pituitary tumor secretes prolactin as well as GH. 

Cozzi R, Attanasio R, Barausse M, Dallabonzana D, Orlandi P, Da Re N, Branca V, Oppizzi G, Gelli D (1998) Cabergoline in acromegaly a renewed role for dopamine agonist treatment Eur J Endocrinol 139. 516-521. 

Therapeutical use dopamine agonist, antiparkinsonian, prolactine inhibitor, treatment of acromegaly 1975... 

The dopamine D2 agonists bromocriptine and cabergoline (pp. 114, 188) inhibit prolactin-releasing AH cells (indications suppression of lactation, prolactin-producing tumors). Excessive, but not normal, growth hormone release can also be inhibited (indication acromegaly) (3). 

Bromocriptine (Parl el) [Antiparkinsonian Agent/Dopamine Receptor Agonist] Uses Parkin on Dz, hyperprolactinemia, acromegaly, pituitary tumors Action Direct-acting on the striatal dopamine receptors X prolactin secretion Dose Initial, 1.25 mg PO bid titrate to effect, w/ food Caution [B, ] Contra Severe ischemic heart Dz or PVD Disp Tabs, caps SE X BP, Raynaud phenomenon (vasospastic disorder resulting in discoloration of the fmgers/toes), dizziness, N, hallucinations Interactions T Effects W/ erythromycin, fluvoxamine, nefazodone, sympathomimetics, antihypertensives X effects W/ phenothiazines, antipsychotics EMS Monitor BP may cause intolerance to EtOH OD May cause NA, severe hypotension give IV fluids symptomatic and supportive... 

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