In a prospective, open-label, multicenter study, 26 RLS patients treated with clonazepam (mean age: 69.2 ± 11.0 years old) were enrolled and then rapidly switched to pramipexole using a conversion calculation of 4:1 for daily doses. Then the daily dose of pramipexole was up titrated or tapered by 0.125 mg/day at each subsequent examination. RLS symptoms and daytime somnolence were evaluated using the International RLS Study Group rating scale (IRLS), Clinical Global Impressions — Severity of illness (CGI-S) and the Epworth Sleepiness Scale (ESS), respectively.
Conversion from clonazepam to pramipexole resulted in significant reductions of IRLS (16.3 ± 8.7 to 9.1 ± 6.3) and ESS (6.5 ± 4.2 to 4.4 ± 3.2). CGI scores demonstrated improvement after conversion. In 4 patients (15 % ), adverse events such as somnolence, sensation of oppression in the lower limbs, diarrhea, or nausea were present. Correlation analysis demonstrated a significant relationship between these daily doses. Spearman's correlation coefficient was 0.662. Our study, however, has some limitations since it is an open-label trial and includes only 26 patients. Further studies using a double-blind design or a crossover design are recommended.
Statistical analysis demonstrated a 4:1 conversion for clonazepam to pramipexole. When switchover from clonazepam to pramipexole is done, this conversion ratio may be helpful to determine the initial dose of pramipexole for treating RLS.