First Parkinson’s drug FDA-approved since 1989
Study: Mirapex reduces levodopa’s side effects
For the first time since 1989, the U.S. Food and Drug Administration has given final approval to a new dopamine-agonist drug to be used in the treatment of Parkinson’s disease.
The drug, pramipexole dehydrochloride tablets, was originally synthesized by Ridgefield, CT-based Boehringer Ingelheim Pharmaceuticals and is being marketed in the United States by Pharmacia & Upjohn under the brand name Mirapex. The anticipated average retail price of the drug is $160 per month.
Just eight days after the FDA’s July 2 approval notification, Pharmacia & Upjohn, based in Kalamazoo, MI, began express-mailing shipments of the drug to pharmacies and drug wholesalers in an effort to meet what the company considers an overwhelming demand on the part of Parkinson’s patients. The eight-day turn-around constitutes Pharmacia & Upjohn’s fastest ever approval-to-distribution turnaround.
The long gap between the approval in 1989 of the Eli Lilly-produced dopamine-agonist Permax and the approval of Mirapex has largely been due to a lack of interest on the part of pharmaceutical companies, says Paul Maestrone, MD, director of scientific and medical affairs at the Staten Island, NY-based American Parkinson’s Disease Association. Although Parkinson’s affects between 500,000 and one million Americans, the disease "is not considered one of the most important diseases from a commercial standpoint," Maestrone says. "It’s not like antibiotics and tranquilizers, which have a much larger piece of the market."
Maestrone adds that the existence of two other dopamine-agonists currently on the market Permax and Bromocriptine, which is produced by Novartis may also have delayed the introduction of new drugs. Nevertheless, says Maestrone, "People are very anxious to try something new. The problem with Parkinson’s disease, though, is that the type of treatment has to be specifically tailored for each individual. [Mirapex] might not work for some people. For others, they may consider it like a miracle."
Although the precise cause of Parkinson’s disease is not known, it’s believed that the disease results in the depletion of neurons in the brain that produce the chemical dopamine, says Baltazar Gomez-Mancilla, MD, a researcher with Pharmacia & Upjohn. The loss of dopamine can cause a loss of motor control. Symptoms typically include tremors, slowed movement, rigidity, and physical instability. Mirapex, like its two main competitors Permax and Bromocriptine, which is produced by Basel, Switzerland-based Novartis is a dopamine-agonist, meaning that it works by targeting, binding to, and stimulating certain dopamine receptors in the brain to enhance motor skill function.
Unlike Permax and Bromocriptine, however, Mirapex has been cleared to treat patients in the early stages of idiopathic, or primary, Parkinson’s disease. It has also been cleared for use in combination with levodopa to treat patients in advanced stages of the disease. Levodopa, the most commonly prescribed medication for the treatment of advanced Parkinson’s disease, serves to replace lost dopamine, says Gomez-Mancilla. Although it’s considered the most effective treatment for advanced Parkinson’s, over the long term, levodopa can cause a host of ugly side effects, including twitching, jerking, and hallucinations.
Shortly following Mirapex’s release, researchers at St. Joseph’s Hospital and Medical Center in Phoenix published a study on the concurrent use of Mirapex and levodopa in the July 1997 issue of Neurology. The research team conducted a 32-week randomized trial of 306 Parkinson’s patients at 26 sites. Patients were either given levodopa and Mirapex in combination or levodopa and a placebo over the course of the study.
The researchers found that, when administered along with levodopa, Mirapex served to reduce the side effects of the other drug and decreased by 27% the amount of levodopa patients needed to maintain function.
Mirapex’s own side effects are similar to those of other dopamine-agonists. In clinical trials conducted by Pharmacia & Upjohn, about 15% of early-stage patients treated with Mirapex experienced nausea, dizziness, drowsiness, and insomnia. Among advanced stage patients, about 15% treated with a combination of Mirapex and levodopa experienced postural hypotension, dyskinesias, extrapyramidal syndrome, insomnia, dizziness, and hallucinations, says Gomez-Mancilla. Postural hypotension, a sudden drop in blood pressure when a patient, for example, stands suddenly after a long period of rest, typically occurs during the initial period of treatment with Mirapex, Gomez-Mancilla adds. Hallucinations can occur at any time during the course of treatment.
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