Since 1968 when levodopa was approved by the FDA to treat Parkinson’s, more effective drugs have been developed. Levodopa is now available in a combination product termed carbidopa-levodopa. There are other formulations which are only marginally better. Motor fluctuations are common with longstanding Parkinson’s, and patients will cycle suddenly from being “on” to “off.” Levodopa has a short half-life in the bloodstream and is inconsistently absorbed depending on the amount of protein in the stomach.
Two new options have recently become available. One is termed Rytary, which is a capsule with immediate and extended release beads of levodopa and carbidopa. It seems to have a longer duration of action and reduces off time. The other is more effective though more difficult to use. It is termed Duopa and is a gel suspension of carbidopa and levodopa, which is infused directly into the intestine through a feeding tube, also called a PEG-J tube. It requires a minor surgical procedure and a pump to infuse the medication. Risks and complications were mainly infection at the site of the tube and various intestinal complications. Excessive dosing may cause dyskinesias, which are involuntary movements.
In the pipeline is liquid levodopa, which is designed to be delivered subcutaneously through a belt pump system similar to an insulin pump. It would not be available before 2018, if at all. There are 2 new pipeline rescue drugs. For years, apomorphine (Apokyn) has been available, given by subcutaneous injection for an off period, but a caregiver is needed to give the injection, and low blood pressure with standing, nausea, and vomiting can occur. There is now a sublingual (meaning under the tongue) thin film strip of apomorphine, which is effective in 10 minutes and lasts 90 minutes and has less side effects. It may be available as early as 2016. Finally, there is a device similar to an asthma inhaler that delivers levodopa as a powder. This starts to work in 10 minutes and lasts 60 minutes. It may also be available in 2016.
Jack Florin, MD
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