Constant infusion of a drug now used intermittently to “rescue” patients with Parkinson’s from bouts of immobility may also help avoid these debilitating symptoms and smooth out their movement throughout the day, physician-scientists say.
“As presently used, this therapy helps bridge a gap,” said Dr. Kapil D. Sethi, neurologist at the Medical College of Georgia Department of Neurology and Movement Disorders Program at Augusta University.
He’s referencing debilitating in-between times when the oral Parkinson’s medication levodopa stops working and patients may experience periods of slow or even no movement without warning. That’s when they may reach for apomorphine, a dopamine receptor agonist currently available in a prefilled syringe, which quickly and directly activates dopamine receptors in the brain. Levels of the neurotransmitter dopamine, which typically enables the brain to control movement, are substantially reduced in Parkinson’s disease as dopamine-producing cells inexplicably become damaged and die.
The nearly 50-year-old standard treatment, levodopa, which is typically taken in tablet or capsule form and converts to dopamine when it reaches the brain, has a short half-life. Most patients must take it four times daily, but those with more advanced disease may need to take it up to eight or nine times, Sethi said. Over time, particularly young patients may experience more bouts of slowness even freezing of movement until their next levodopa dose kicks in. That in-between time is when some patients now reach for the injectable form of apomorphine as a rescue.