Levodopa is the most commonly used pharmacological intervention for Parkinson’s disease (PD). Levodopa is capable of crossing the blood brain barrier (BBB), unlike dopamine itself, and is converted into dopamine by the enzyme L-aromatic amino acid decarboxylase (DOPA decarboxylase). Levodopa is therefore a dopamine precursor that requires functional dopaminergic neurons or dopamine production machinery to work. Its effectiveness decreases as either dopaminergic neurons or the production machinery are lost. Since the actions of levodopa are only required in the brain and DOPA decarboxylase is also present outside the central nervous system, levodopa is usually administered with the DOPA decarboxylase inhibitor carbidopa, which cannot cross the BBB. Combined levodopa/carbidopa is available as a viscous gel that is administered by continuous infusion in the duodenum via a permanent tube. This preparation, also known as duodopa, is not only rapidly absorbed but also released at a steady rate resulting in stable plasma concentrations. More information about levodopa and duodopa can be found on the EPDA website.