Recently, the U.S. Food and Drug Administration (FDA) approved a new drug for Parkinson's symptoms called Osmolex ER (amantadine extended-release). Osmolex ER is the third amantadine-based medication for Parkinson's disease (PD), and joins Symmetrel (immediate-release amantadine) and Gocovri (extended-release amantadine). Amantadine works on two brain chemical systems involved in PD: dopamine and glutamate.
More options can be better, but they also can be confusing. Here we talk about these drugs' similarities and differences and why you might consider one over another.
Let's start with Symmetrel (immediate-release amantadine). What is that?
This drug is sometimes used alone to treat mild symptoms in early Parkinson's. But doctors often prescribe it for dyskinesia (involuntary, uncontrolled movements) even though it is not specifically FDA approved for that. Immediate-release amantadine is taken two or three times per day and may cause insomnia, nausea, dizziness and purple-red blotchy spots on the skin. People with kidney problems might need a lower dose.
What about Gocovri (extended-release amantadine)?
This once-a-day formulation is FDA approved for the treatment of dyskinesia. It also may help avoid symptoms coming back because other medications aren't working well ("off" time). Gocovri is taken at bedtime so that the medication levels are highest during the day, when dyskinesia typically is most bothersome. Gocovri could cause hallucinations (seeing things that aren't there), dizziness, dry mouth, swelling of the legs and feet, constipation and falls. Those with kidney problems may need to decrease the dose.
What is Osmolex ER (amantadine extended-release)?
Like immediate-release amantadine, Osmolex ER treats Parkinson's symptoms, such as slowness, stiffness and tremor. (It does not have FDA approval for dyskinesia.) Unlike immediate-release amantadine, Osmolex ER is taken once a day, in the morning. Potential side effects and the need for a lower dose with kidney problems are similar.
A small group of control volunteers without PD tested Osmolex ER. This study showed that the drug was essentially the same as immediate-release amantadine with regard to where it goes in the body and how it works. The FDA approved Osmolex ER based on this and other data comparing the two drugs. (This is how generic drugs are approved too.) As doctors and patients use this medication, we'll learn more about how it's tolerated and how well it works.
Which version of amantadine should you take?
When thinking about any Parkinson's medication, you and your doctor will consider several factors: what symptoms you're treating, a drug's potential side effects and benefits, and cost, for example.
If you're aiming to ease mild symptoms, you and your doctor may consider immediate-release amantadine or Osmolex ER. For dyskinesia, you might look to Gocovri as this is the only FDA-approved drug for this condition. Note that doctors used immediate-release amantadine "off label" to treat dyskinesia before Gocovri was available. In some cases, this may still be the best option.
Work with your doctor to find the regimen that works best for you and your symptoms. For more on thinking about newly approved therapies, read our blog. For more on these and other Parkinson's medications, visit our webpage.