Parlodel
Meaning of Parlodel: A dopamine-mimicking tablet best known for shrinking pituitary tumors that flood the body with the milk hormone.
Definition of Parlodel
Parlodel is a brand name for bromocriptine mesylate, a drug that stimulates dopamine receptors in the brain. Dopamine is the natural brake on prolactin, the hormone that drives milk production, so the drug lowers prolactin levels and shrinks tumors that secrete it. It has also been used in excess growth hormone and in Parkinson disease.
What does it treat?
| Condition | What the drug does |
|---|---|
| Prolactin-secreting pituitary tumor | Lowers prolactin and physically shrinks the tumor, often restoring periods and fertility |
| Raised prolactin from other causes | Reduces milk discharge and restores the menstrual cycle |
| Acromegaly | Lowers growth hormone in a minority of cases, now a secondary option |
| Parkinson disease | Substitutes for lost dopamine signaling, now used far less than newer drugs |
Why does blocking dopamine do the opposite?
Prolactin is unusual among pituitary hormones because the brain holds it back rather than switching it on, and dopamine is what applies the brake. Anything that stimulates dopamine receptors therefore lowers prolactin, and anything that blocks them raises it. That is why antipsychotic drugs, which block dopamine receptors in the treatment of schizophrenia, commonly cause milk discharge, breast enlargement and missed periods. Bromocriptine works in the opposite direction on the same receptor.
What does the mesylate part mean?
It is the salt the drug is supplied as, formed with methanesulfonic acid, chosen because it is stable and dissolves predictably. The active molecule is unchanged. Many medicines are dispensed this way, among them doxazosin mesylate, and the salt is not part of the drug's action.
What are the drawbacks?
Nausea is the commonest complaint, along with headache, nasal stuffiness and dizziness on standing, since the drug also lowers blood pressure. Doses are usually built up gradually for that reason. Bromocriptine is derived from ergot, a fungus with a long medical history, and prolonged use at high doses has been associated with fibrous thickening of heart valves and of the linings around the lungs. A related drug, cabergoline, is taken less often and is generally better tolerated, so it has displaced bromocriptine as the usual first choice for a prolactin-secreting tumor. Sudden sleep episodes and impulse control problems are recognized with dopamine agonists as a class.
Also known as
Used in a sentence
Bromocriptine mesylate was started for a prolactin-secreting pituitary adenoma.
Good to know
Bromocriptine is derived from ergot, and prolonged use at high doses has been linked with fibrous thickening of heart valves and of the linings around the lungs.