Single-dose studies of a slow-release preparation of levodopa and benserazide (Madopar HBS) in Parkinson's disease.

The clinical effects and pharmacokinetic profiles of single doses of Madopar HBS were compared with those of standard Madopar in two studies in patients with Parkinson's disease and 'on-off' fluctuations. In the first study, 10 fasting patients received equivalent doses (200 mg levodopa plus 50 mg benserazide) of each preparation. The clinical response to Madopar HBS was delayed and brief; the relative bioavailability was only 50%. In the second study in 7 non-fasted patients, the effects of 3 capsules of Madopar HBS 125 were compared with those of 2 capsules of standard Madopar 125. Delay to turn on was longer with HBS, but duration of time on, and delay to turn off, were longer with this preparation. The area under the concentration-time curve for plasma levodopa was greater with HBS, and the maximum levodopa concentration was similar to, but achieved later than standard Madopar.