title: The effect of ascorbic acid on the pharmacokinetics of levodopa in elderly patients with Parkinson disease.
abstract: Levodopa (LD) is one of the most effective drugs for clinical symptoms in patients with Parkinson disease (PD). Most PD patients are advanced in age and may have trouble with LD absorption because aging influences drug absorption processes. Previous reports have indicated that ascorbic acid (AsA) can reduce LD dosage without losing its effectiveness. The current study sought to determine whether AsA affects LD absorption in elderly PD patients. Sixty-seven elderly PD patients took a tablet orally containing 100 mg LD and 10 mg carbidopa following an overnight fast. Plasma LD concentrations were determined at 6 points up to 3 hours, using high-performance liquid chromatography with electrochemical detection. The area under the curve (AUC), peak drug concentration (Cmax), and time to peak drug concentration (Tmax) were calculated. The pharmacokinetic evaluation was repeatedly performed 1 week later in the same way except for adding 200 mg AsA to the tablet. The changes in AUC, Cmax, and Tmax between the tests were evaluated. Significant changes in these parameters were not observed when analyzed using data from all patients. However, significant increases in AUC and Cmax, and a significant reduction in Tmax by adding AsA were observed in 25 patients with baseline AUC < or =2500 ng.hour/mL. In conclusion, AsA can improve LD absorption in elderly PD patients with poor LD bioavailability. LD therapy in combination with AsA may be one of the strategies for PD treatment.
authors.affiliation: Second Department of Internal Medicine, Nippon Medical School, Tokyo, Japan. nagaya2@attglobal.net
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nagayama
authors.forename: Makoto
authors.initials: M
authors.lastname: Hamamoto
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ueda
authors.forename: Chikako
authors.initials: C
authors.lastname: Nito
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Katayama
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000975:Antioxidants / Q000494:pharmacology* / Q000627:therapeutic use; D000978:Antiparkinson Agents / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D019540:Area Under Curve; D001205:Ascorbic Acid / Q000494:pharmacology* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007980:Levodopa / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000188:drug therapy / Q000378:metabolism*; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D000975:Antioxidants; D000978:Antiparkinson Agents; D007980:Levodopa; D001205:Ascorbic Acid