The maker of a Parkinson's drug is voluntarily pulling the drug from the market in Canada and the U.S. because of the risk of damage to heart valves.

Pergolide mesylate, sold under the brand name Permax, is in a class of drugs called dopamine agonists, which stimulate the brain production of the neurotransmitter dopamine.

Although Permax was originally brought to market by Eli Lilly, it is now marketed in the United States by Valeant Pharmaceuticals International and in Canada by Shire.

While IMS Health Canada, a company that collects information on pharmaceutical consumption trends, reports there were nearly 21,00 prescriptions for the medication in Canada last year, it is not the main treatment for Parkinson's. 

Other drugs in the same class can be substituted, said Dr. Robert Temple of the U.S. Food and Drug Administration's office of drug evaluation. 

"Our conclusion is that pergolide has no demonstrated advantage over other therapies," Temple told a briefing Thursday.

Heart valve side-effect

The withdrawal follows the publication of two studies in January that showed the risks of Permax were higher than thought.

The studies confirmed pervious findings linking pergolide with an increased chance of valvular heart disease.

Patients taking Permax should not stop taking the drug abruptly, Health Canada and the FDA said. If patients along with their doctor conclude they need a dopamine agonist, there are ways to switch safely.

Moderate to severe valve problems were seen in 23 per cent of people taking pergolide in one of the studies, but the problem did not occur for other drugs in the same class.

Valve replacement surgery is the only solution to the leaky heart valve side-effect.

Symptoms of valve disease include extreme weakness, shortness of breath, pain in the chest and difficulty with exertion.

Options available

The voluntary withdrawal is not immediate for pharmacies, allowing doctors and patients time to discuss options and change treatments if needed.

Parkinson's disease is a disease of the nervous system. Classic signs of the disease are:

• Resting tremor on one side of the body (an arm or a leg shakes even when the muscles are at rest and you are completely relaxed).
• Generalized slowness of movement.
• Stiffness of limbs (rigidity).
• Gait or balance problems.

The disease, which is caused by a lack of dopamine in the brain, progresses slowly. The drug levodopa, which the body converts to dopamine, is the main treatment.

It's estimated that approximately 100,000 Canadians have Parkinson's disease.

With files from the Associated Press