Long-term retention rate of pramipexole in the treatment of Parkinson’s disease

Abstract

To the editor: In a recent retrospective study, Arbouw et al. [1] reported that 60% of patients treated with pramipexole (PRX) due to Parkinson’s disease (PD) discontinued the drug within 3 years. The patients were identified from a neurology department of a large teaching hospital in The Netherlands, and the discontinuation rates were based on prescription data from community pharmacies. We have assessed longterm retention rate of patients on PRX therapy based on hospital records and sought to identify risk factors underlying the discontinuation of PRX. Using the patient records of Tampere University Hospital (Finland), we retrospectively identified all patients with idiopathic PD treated either as inor outpatients at the Department of Neurology between 1 January 1999 and 31 December 2005. We included patients who had been prescribed PRX and for whom data were available from at least one follow-up visit. From the hospital records on patient demographics, age at onset and duration of PD, we obtained information on possible motor (treatment-related fluctuations, dyskinesia) and non-motor complications (e.g. orthostatic hypotension, hallucinations etc.) and previous concomitant PD drugs and their doses prior to and during PRX treatment. The cause and time of possible discontinuation of PRX was recorded. The retention rate (i.e. the proportion of patients continuing on PRX medication) was estimated using the Kaplan–Meyer method [2]. Follow-up commenced at the introduction of PRX into the treatment program and ended at the discontinuation of treatment or closing date. The effect of different factors on retention rate was examined using Cox regression analysis [3]. A total of 94 patients (33 women, 61 men) fulfilled the study criteria. The mean age of the patient cohort at the onset of PD was 59 (standard deviation 11) years, and the duration of the disorder before the initiation of PRX therapy was 6.5 (SD 6) years. Motor fluctuations prior to the introduction of PRX were recorded in 37 patients (39%). At the initiation of PRX treatment, 66 patients (70%) were on levodopa, 30 (32%) used selegiline, 19 (20%) used entacapone and 15 (16%) used other antiparkinsonian drugs. At the last followup, 72 patients were still using PRX. Figure 1 shows the estimated rate of patient continuation on PRX. At 1 year, 76% of the patients were still on PRX; the rate at 3 and 6 years was 63%. The mean maintenance dose of PRX was 1.05 mg/day (as base; corresponding approximately to 1.5 mg as salt). Of the 94 patients, 14 (15%) discontinued PRX due to adverse effects, and eight (9%) discontinued due to insufficient therapeutic effects. The most common adverse effects leading to discontinuation were confusion (three patients), hallucinations (three patients) and nausea (two patients). Other reasons of discontinuation included dyskinesia, orthostatic hypotension and miscellaneous symptoms. Eur J Clin Pharmacol (2009) 65:955–956 DOI 10.1007/s00228-009-0661-4