Dopamine agonists prolactinomas

A dopamine agonist is the usual initial treatment for prolactinomas. Significant reduction in both tumor size and serum prolactin levels occurs in about 85% of those receiving these drugs for 6 months or longer. 

Quinagolide (CV 205-502, Norprolac) in doses of 0.15-0.6 mg/d orally, suppresses prolactin and shrinks most prolactinomas. It also decreases cyclic mastodynia. Quinagolide is sometimes better tolerated than ergot-derived dopamine agonists. It is not available in the USA. 

As much as higher concentrations of dopamine are required to stimulate striatal adenylate cyclase activity as compared to the affinity of the drug for the agonistic sites of the receptor, the sensitivity of the anterior pituitary adenylate cyclase to dopamine agonists in both human prolactinoma (26) and rat adenohypophysial homogenate (31) is lower than the potency of the compounds to inhibit prolactin secretion in intact cells (2). This variable loss of sensitivity upon cell homogeneization is a phenomenon frequently observed in other systems (32). 

Kars M, Delgado V, Holman ER, Feelders RA, Smit JW, Romijn JA, Bax JJ, Pereira AM. Aortic valve calcification and mild tricuspid regurgitation but no clinical heart disease after 8 years of dopamine agonist therapy for prolactinoma. J Clin Endocrinol Metab 2008 93 (9) 3348-56. 

Another study evaluated whether the long-term use of ergot-derived dopamine agonists for hyperprolactinemia may be associated with increased risk of significant valvular heart disease. A total of 74 patients (mean age 48 1.4 years, 23% male) with prolactinoma treated with the drugs for at least lyear were evaluated with... 

Delgado V, Biermasz NR, van Thiel SW, Ewe SH, Marsan NA, Holman ER, et al. Changes in heart valve stmcture and function in patients treated with dopamine agonists for prolactinomas, a 2-year follow-up study. Clin Endocrinol (Oxf) 2012 77(1) 99-105. 

Gkekas N, Primikiris P, Georgakouhas N. Untethering of herniated left optic nerve after dopamine agonist treatment for giant prolactinoma. Acta Neurochir (Wien) 2013 155(3) 495-6. 

Mectianism of Action Agonist at dopamine Dj receptors suppressing prolactin secretion. Therapeutic Effect Shrinks prolactinomas, restores gonadal function, improves symptoms of Parkinson s disease. 

Bromocriptine was the first D2-receptor agonist to be used in the treatment of hyperprolactinemia and has been the mainstay of therapy for over 20 years. It inhibits the release of prolactin by directly stimulating postsynaptic dopamine receptors in the hypothalamus. Hypothalamic release of dopamine (prolactin-inhibitory hormone) inhibits the release of prolactin. Decreases in serum prolactin concentrations occur within 2 hours of oral administration with maximal suppression occurring after 8 hours, and suppressive effects persisting for up to 24 hours. Medical therapy with bromocriptine normalizes prolactin serum concentrations, restores gonadotropin production, and shrinks tumor size in approximately 90% of patients with prolactinomas. ... 

Colao A, di Sarno A, Pivonello R, et al. Dopamine receptor agonists for treating prolactinomas. Expert Opin Investig Drugs 2002 11 787-800. 

Bromocriptine (PARLODEL) is the dopamine-receptor agonist against which newer agents are compared. Bromocriptine is a semisynthetic ergot alkaloid that interacts with dopamine receptors to inhibit spontaneous and TRH-induced release of prolactin to a lesser extent, it also activates Dj receptors. Bromocriptine normalizes serum prolactin levels in 70-80% of patients with prolactinomas and decreases tumor size in more than 50fo of patients, including those with macroadenomas. 

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