title: Controlled-release carbidopa/levodopa (Sinemet 50/200 CR4): clinical and pharmacokinetic studies.
abstract: Several controlled-release carbidopa/levodopa preparations have been formulated to achieve a more stable and extended antiparkinsonian action. The most effective is Sinemet CR (Sinemet CR4), with an erodible polymer matrix that retards release of levodopa. In 19 parkinsonians with prominent dose-by-dose fluctuations, double-blind crossover trials comparing 8-week regimens of standard carbidopa/levodopa (25/100) to Sinemet CR (50/200) showed comparable clinical outcomes, with mean daily dosing for optimal control reduced from 10.2 to 5.4 (although mean daily levodopa dosage increased from 1,340 to 1,781 mg/day). Most patients improved on the Sinemet CR regimen in hours "on" and in ratings of clinical state and disability. With pharmacokinetic studies correlated to clinical ratings, plasma levodopa was less variable during Sinemet CR treatment, and clinical responses showed greater uniformity. Compared to standard Sinemet 25/100, time to peak levodopa concentration (2.3 versus 1.1 hrs), onset of maximal clinical improvement (2.2 versus 1.1 hrs), and other indices were significantly delayed with Sinemet CR. Levodopa bioavailability and clearance were similar between formulations. Although onset of clinical response is slower, the Sinemet CR formulation lessens peak-dose and "wearing-off" responses occurring with conventional carbidopa/levodopa and offers substantial improvement for some parkinsonians.
authors.affiliation: Clinical Neuroscience Program, Sinai Hospital of Detroit, MI 48235.
authors.forename: P A
authors.initials: PA
authors.lastname: LeWitt
authors.forename: M V
authors.initials: MV
authors.lastname: Nelson
authors.forename: R C
authors.initials: RC
authors.lastname: Berchou
authors.forename: M P
authors.initials: MP
authors.lastname: Galloway
authors.forename: N
authors.initials: N
authors.lastname: Kesaree
authors.forename: D
authors.initials: D
authors.lastname: Kareti
authors.forename: P
authors.initials: P
authors.lastname: Schlick
mesh_terms: D000368:Aged; D000978:Antiparkinson Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D002230:Carbidopa / Q000008:administration & dosage* / Q000493:pharmacokinetics; D002986:Clinical Trials as Topic; D003692:Delayed-Action Preparations; D004311:Double-Blind Method; D004338:Drug Combinations / Q000008:administration & dosage / Q000493:pharmacokinetics; D006801:Humans; D007980:Levodopa / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics; D008875:Middle Aged; D010300:Parkinson Disease / Q000097:blood / Q000188:drug therapy*; D011897:Random Allocation; D014443:Tyrosine / Q000097:blood / Q000031:analogs & derivatives
chemical_list: D000978:Antiparkinson Agents; D003692:Delayed-Action Preparations; D004338:Drug Combinations; C009265:carbidopa, levodopa drug combination; D014443:Tyrosine; D007980:Levodopa; D002230:Carbidopa; C008404:3-methoxytyrosine