A higher dose of carbidopa, in combination with usual doses of levodopa and entacapone, can reduce ‘off-time’ in patients with fluctuating Parkinson’s disease, compared with standard levodopa/carbidopa combinations, according to results from an early clinical trial.

The finding casts doubt on whether the current levodopa and carbidopa ration of 4:1 is optimum, says lead researcher Dr Claudia Trenkwalder of the University Medical Centre of Goettingen, Germany.

“This is a surprising result,” she said.

The randomised phase 2 proof-of-concept study to test whether increased fixed carbidopa doses of 65mg or 105mg in combination with 75mg, 100mg, 125mg, or 150mg of levodopa and 200mg of catechol-O-methyltransferase (COMT) inhibitor entacapone reduced off-time, compared with the standard combination of 4:1 levodopa/carbidopa and entacapone (control).