LETTER TO THE EDITORS
Long-term retention rate of pramipexole in the treatment
of Parkinson’s disease
Tapani Keränen
&
Mervi Tuhkasaari
&
Hanna Kuusisto
Received: 16 April 2009 / Accepted: 20 April 2009 /Published online: 5 May 2009
#
Springer-Verlag 2009
Keywords Outcome
.
Parkinson’s disease
.
Pramipexole
.
Retention rate
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 long-
term 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 in- or
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, dyski-
nesia) and non-motor complications (e.g. orthostatic
hypotension, hallucinations etc.) and previous concomi-
tant 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 follow-
up, 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
T. Keränen
:
H. Kuusisto
Division of Neurology and Rehabilitation,
Tampere University Hospital,
P.O.B. 2000, Tampere, Finland
T. Keränen (*)
:
M. Tuhkasaari
Department of Pharmacology and Toxicology,
University of Kuopio,
P.O.B. 1627 Kuopio, Finland
e-mail: tapani.keranen@uku.fi