Dr. Thomas Davis: If you are a device manufacturer for DBS it is natural for you to aim to make better devices, better batteries, better programming, and better electrodes than your competitor. That's really where the industry-based research is right now. Clinicians are still determining which device is the best candidate, where the best target in the brain is, and when to use DBS.
When would a health care practitioner decide to try frequent smaller dosages or immediate-release formulations of dopaminergic drugs to control levodopa-induced dyskinesia (LID), compared with non-dopaminergic treatments that are available? What are some pros and cons of each approach?
Dr. David Charles : If you have a patient who's already on levodopa, it's not uncommon that—separate from the way we prescribe the medicine—the patients experiment with their medicine to some degree. At the very least, people occasionally forget to take a dose and they feel the effect of a missed dose. They may take an extra dose or an extra half dose, particularly if they feel that the last dose isn't working as well, or in the event they have some special occasion coming up.
Over time, patients and physicians learn that sometimes smaller, more frequent dosing of levodopa can be a helpful strategy for certain individuals. One advantage is that it's the medication that the patient is already taking, and they're just simply breaking tablets. Many pharmacies will break tablets for patients so they can take some smaller doses more frequently. Obviously, there can be downsides to that, such as it becoming harder to remember to take more frequent doses.
Dr. Thomas Davis: I would agree that the biggest advantage of taking more frequent, smaller doses is that it's cheaper than adding an adjunct or moving to a more invasive therapy. More frequent smaller doses of levodopa also generally has no side effects because if you're taking 2 carbidopa/levodopa 3 times a day and you're tolerating it, but you're having peak dose problems, you can then switch to 1.5 tablets 4 times a day. It involves more work and planning, but it's no more total medication than the patient is taking already, so this strategy usually does not have any unexpected side effects. It really boils down to how much work the patient wants to put in, how adherent they are to medication dosing, and whether they want to add another medication.
Most of the adjunctive medications to treat motor fluctuations are approved to improve on-time in Parkinson's disease patients with wearing off. These include the monoamine oxidase inhibitors, COMT inhibitors, and adenosine A2A antagonists. For treatment of dyskinesia, only the extended release capsule formulation of amantadine has FDA approval, although all formulations are approved for Parkinson's disease and are used clinically to dampen dyskinesia. How long to try these strategies before moving to one of the more advanced therapies, like DBS or jejunal infusion of levodopa, is not clear. It's great to have options, but it makes the decisions a lot harder.
Dr. David Charles: Dr. Davis raised the question of what medicine to choose, and what's your next choice in a patient who's having wearing-off dyskinesia or LID and so forth. There is an increasing number of options for those mid-stage patients. The pitfall is feeling that you have to try every available medication and combination before moving to a more advanced therapy. The physician risks churning through the various combinations for so long that the benefit of an advanced therapy becomes shortened or lost altogether.