The drug, approved in 1996 by the U.S. Food and Drug Administration (FDA) for the treatment of the hormone deficiency known as hyperprolactinaemia, is commonly used to treat Parkinson's in other parts of the world, and has been known to creep onto prescription pads for Parkinson's in the United States.
However this is off-label territory - a slippery slope - and the concern over Dostinex in higher dosages more commonly associated with Parkinson's, remains the link to potential heart issues, and specifically valvular heart disease.
In Parkinson's patients, Dostinex targets the areas of the brain that have become deficient due to the onset of the disease - namely the depletion of dopamine, which results from the degeneration of neurons in the brain that control movement. Dostinex, in layman's terms, has the capacity to mimic the effects of dopamine in the brain, and positively impacts areas such as muscle control and motor skills, and helps with the stiffness and tremors often associated with Parkinson's.While effective, the dosage required for Parkinson's patients is upwards of 40 times higher than levels required for the approved application with hyperprolactinaemia hormone disorder.
It is within the context of these higher dosages that studies have uncovered the link between Dostinex and heart valve problems. In two recent clinical trials conducted outside of the United States, Dostinex was found to contribute a higher risk for heart valve disease, compared to patients taking some other form of medication to control Parkinson's. An Italian study in Milan found that 29 per cent of trial participants taking Dostinex were seen to have heart valve damage in the moderate to severe range. Meanwhile, in Germany, respondents were found to be seven times at risk for leaking heart valves, than those not taking Dostinex.
Other side effects identified range from nausea, to dry mouth, to vertigo. However, the concern over the potential for heart disorders remains uppermost in people's minds.
For its part, the FDA remains satisfied that despite the risks for unapproved, off-label use, the potential for heart valve damage in Americans is minimized so long as the drug is used for which it was originally intended, and approved. Recommended dosage levels for the treatment of hyperprolactinaemia are well below a threshold that has any negative impact on the heart.
Dostinex is manufactured, and marketed in The United States and Canada by Pfizer. U.S. sales of the drug exceed U.S $80 million a year. It is known generically as cabergoline, and is considered completely safe in the lower dosages associated with hormonal therapy.
There remains, however, a serious risk to the heart in patients taking higher dosages required for the treatment of Parkinson's. Patients with a history of, or currently taking Dostinex for Parkinson's should consult their doctor - especially if any of the more serious risk factors, including leaky valve syndrome, are known to be present or suspected.
A leaking heart valve does not close tightly, which allows blood to run, or 'leak' backwards across the valve. This makes the heart work harder, and can often restrict blood flow to other parts of the body. Leaky valve disease almost always requires surgery to correct.
The two studies linking high dosages of Dostinex with valve disease appeared in the New England Journal of Medicine, in January of this year.