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September 1993

Poor Tolerability of MK-458

Author Affiliations

California Clinical Trials 8500 Wilshire Blvd, Seventh Floor Beverly Hills, CA 90211
Division of Clinical Neurosciences Merck Research Laboratories West Point, PA 19486

Arch Neurol. 1993;50(9):896. doi:10.1001/archneur.1993.00540090007003

To the Editor.  —We were pleased to read the article entitled "Dopamine Agonist Treatment of Fluctuating Parkinsonism,"1 which focuses on the relative contributions of D1 and D2 receptors to the efficacy and adverse experience profile of dopamine agonist treatment. We have recently published data on the pharmacokinetics and dose proportionality, efficacy, and safety of MK-458 (HPMC [hydroxypropyl methylcellulose]), a sustained release pure D2 agonist in patients with parkinsonism.2Patients with stages I through III disease were titrated to 18 mg of MK-458 (HPMC) twice a day over 1 month, followed by a 36-hour washout. All patients then received, in a four-period crossover, 6, 12, and 18 mg of oral MK-458 (HPMC) and 40 μg of intravenous MK-458.The terminal half-life of MK-458 after oral sustained release administration is 3.8 hours, and bioavailability is estimated at 4.1% to 4.9%; maximum plasma concentration, Cmax, is reached

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