Old Drugs, New Delivery Systems in Parkinson's Disease.

Levodopa is the mainstay of treatment in Parkinson's disease (PD). As the disease progresses, variations in plasma levodopa levels lead to motor fluctuations. The common reasons behind variations in the plasma levels include delayed gastric emptying, small intestinal bacterial overgrowth, protein interaction with levodopa absorption, and limited oral bioavailability of levodopa. Efforts to find newer delivery systems for older drugs to avoid the problems associated with oral delivery of medications are continuing. This review aims to provide up-to-date information about the newer delivery options for drugs used for PD and provides a summary of infusion therapy with apomorphine, modifications to other dopamine agonists, various oral formulations of carbidopa/levodopa, inhaled levodopa, intrajejunal infusion of levodopa, and sublingual apomorphine. The advantages, dose, and adverse effects of each treatment modality are reviewed. We also discuss several drugs under investigation, such as the subcutaneous carbidopa/levodopa infusion and subcutaneous rotigotine.