title: Plasma amantadine concentrations in patients with Parkinson's disease.
abstract: We determined plasma amantadine concentrations in patients with Parkinson's disease (PD) in daily clinical practice and investigated the relationship between plasma concentration and adverse reactions to clarify the safe therapeutic range. Seventy-eight consecutive PD patients on stable amantadine treatment were recruited. Plasma concentration of amantadine was measured 3h after the administration of morning amantadine dose. Serum creatinine was measured to estimate renal function. The mean daily dose of amantadine was 135.1+/-62.3mg/day, and the mean plasma amantadine concentration was 812.5+/-839.5 ng/ml (range, 91-4400 ng/ml). Plasma amantadine concentration increased according to increasing renal dysfunction. Three patients exhibited adverse reactions, such as myoclonus, hallucinations, and delirium, and all of them showed plasma amantadine concentration >3000 ng/ml. None of the three cases had previously shown such side effects. PD patients who have not developed any psychiatric symptoms as adverse reactions to the treatment may develop myoclonus, hallucination, or delirium when the plasma concentration of amantadine exceeds 3000 ng/ml. It is therefore recommended to use amantadine at the plasma concentration of less than 3000 ng/ml in the treatment of Parkinson's disease, especially in elderly patients.
authors.affiliation: Department of Medicine (Neurology), Ehime University Graduate School of Medicine, Shitsukawa Tohon, Ehime 791-0295, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Nishikawa
authors.forename: M
authors.initials: M
authors.lastname: Nagai
authors.forename: T
authors.initials: T
authors.lastname: Moritoyo
authors.forename: H
authors.initials: H
authors.lastname: Yabe
authors.forename: M
authors.initials: M
authors.lastname: Nomoto
mesh_terms: D000328:Adult; D000368:Aged; D000547:Amantadine / Q000009:adverse effects* / Q000097:blood* / Q000627:therapeutic use; D000978:Antiparkinson Agents / Q000009:adverse effects / Q000097:blood* / Q000627:therapeutic use; D003404:Creatinine / Q000097:blood / Q000378:metabolism; D003693:Delirium / Q000139:chemically induced; D005260:Female; D006212:Hallucinations / Q000139:chemically induced; D006801:Humans; D008297:Male; D008875:Middle Aged; D009207:Myoclonus / Q000139:chemically induced; D010300:Parkinson Disease / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D012720:Severity of Illness Index
chemical_list: D000978:Antiparkinson Agents; D003404:Creatinine; D000547:Amantadine