Opioid-induced constipation, tardive dyskinesia, and other medication-induced syndromes present worthwhile revenue opportunities for pharmaceutical R&D.
In the 1960s, researchers discovered that the loss of motor control from Parkinson’s disease (PD) was tied to a deficiency of dopamine in a part of the brain involved in the coordination of movement.
Evidence soon established that administration of levodopa, a dopamine precursor molecule, dramatically improved PD symptoms. Here’s the catch: relief of symptoms was accompanied by severe nausea and vomiting. Levodopa was not only being converted to dopamine in the brain but also in the bloodstream, activating dopamine receptors in the peripheral nervous system and causing the adverse side effects.