New pharmacotherapy for Parkinson's disease.

OBJECTIVE: To summarize the development, pharmacology, pharmacokinetics, efficacy, and safety of five investigational antiparkinsonian drugs that are in or have recently completed Phase III trials: three dopamine agonists, pramipexole, ropinirole, and cabergoline; and two catechol-O-methyltransferase (COMT) inhibitors, entacapone and tolcapone. The pathophysiology and the role of dopamine in Parkinson's disease are also reviewed. DATA SOURCES: A MEDLINE search of relevant English-language literature, clinical studies, abstracts, and review articles pertaining to Parkinson's disease was conducted. Manual searches of 1996/1997 meeting abstracts published by the American Academy of Neurology and the Movement Disorders Society were also performed. Manufacturers provided unpublished Phase III trial efficacy and pharmacokinetic data. STUDY SELECTION AND DATA EXTRACTION: Clinical trial investigations selected for inclusion were limited to human subjects. Interim analyses after 6 months for long-term clinical studies in progress were included. Pharmacokinetic data from animals were cited if human data were unavailable. Statistical analyses for all studies were evaluated. DATA SYNTHESIS: By selectivity targeting D2 receptors, the newer dopamine agonists (i.e., cabergoline, pramipexole, ropinirole) may delay the introduction of levodopa and thus the occurrence of levodopa-induced dyskinesias. In addition, they are efficacious as adjunctive therapies in patients with advanced Parkinson's disease. Unlike the currently available dopamine agonists, pramipexole and ropinirole are non-ergot derivatives and do not cause skin inflammation, paresthesias, pulmonary infiltrates, or pleural effusion. The COMT inhibitors, tolcapone and entacapone, improve the pharmacokinetics of levodopa by preventing its peripheral catabolism and increasing the concentration of brain dopamine; thus, these agents may reduce the incidence of "wearing-off" effects associated with the short half-life of levodopa and the progression of Parkinson's disease. CONCLUSIONS: Interim 6-month analyses of pramipexole, ropinirole, and cabergoline for symptomatic treatment of early Parkinson's disease have shown these drugs to be efficacious and relatively well-tolerated when used as monotherapy. Their role in delaying the development of motor fluctuations and delaying the addition of levodopa is the subject of long-term clinical studies. In advanced stages of Parkinson's disease, these medications were also efficacious; however, the main adverse effects included dyskinesias, somnolence, and hallucinations. The COMT inhibitors, entacapone and tolcapone, have also demonstrated efficacy in improving on-time in patients with stable disease. Tolcapone has also demonstrated efficacy in patients with motor fluctuations. Both drugs are relatively well-tolerated, with the exception of dyskinesias that require reduction of the levodopa dosage and occasional diarrhea.

Variable disposition of ciprofloxacin in critically ill patients undergoing continuous arteriovenous hemodiafiltration.

Continuous arteriovenous hemodiafiltration (CAVHD) is being used increasingly in critically ill patients with acute renal failure (ARF). We prospectively evaluated extracorporeal and total systemic clearances (ClCAVHD and Cls) of ciprofloxacin during CAVHD in four patients with severe ARF to assess the adequacy of drug dosing. Ciprofloxacin serum and ultrafiltrate concentrations were measured by high-performance liquid chromatography. The ClCAVHD accounted for approximately 5.9% (range 2.8-11.6%) of Cls of ciprofloxacin. However, large variability in serum concentrations was observed with the normally recommended dose of 400 mg/day, and doses of up to 800 mg/day were required to maintain concentrations suitable for treatment of serious infections. High daily doses of ciprofloxacin required in these patients are likely related to altered pharmacokinetics in serious illness as well as to the increased extracorporeal clearance during CAVHD. Clinical studies to define appropriate dosing recommendations for ciprofloxacin during CAVHD are necessary to guide clinicians in optimum drug use.