Piribedil and bromocriptine in Parkinson's disease: a single-blind crossover study.
BACKGROUND
Clinicians switch from one dopamine agonist to another for various reasons. However, each change may inadvertently result in certain potential risks such as decreased medication efficacy or new side-effects.


OBJECTIVE
We evaluated the tolerability of a switch of bromocriptine to piribedil using two conversion ratios as a primary outcome measure, with motor function as a secondary outcome measure, in patients with mild to moderate Parkinson's disease (PD).


METHODS
Twenty consecutive patients with mild to moderate PD (Hoehn and Yahr, stage II-III) on treatment with stable doses of bromocriptine and levodopa were randomized to two groups of 10 patients each, to receive piribedil based on 1:5 or 1:10 conversion ratios. Blinded evaluations were performed: 1) United Parkinson's Diseased Rating Scale (UPDRS) scores both in 'on' and 'off', 2) Open-ended interviews for adverse events, 3) Epworth Sleepiness Scale, 4) Purdue Pegboard assessment during 'on' and 'off', 5) Hand-arm movement test during 'on' and 'off', and 6) Walking test during 'on' and 'off'.


RESULTS
Major adverse events included 'sleep attacks' in one patient and minor side-effects included giddiness, nausea, hallucinations, sleepiness and lethargy. However, these were mild and 19 (95%) of the 20 patients completed the study. There was a significant improvement in both the UPDRS 'off' total and motor scores at 1 month compared with baseline for the group on 1:10 ratio. The walking times during the 'off' state at 1 and 2 months were significantly better compared with baseline in the 1:5 group. There were otherwise no significant differences in the rating tests during both 'off' and 'on' states before and after the bromocriptine switch.


CONCLUSIONS
We demonstrated that patients with mild to moderate PD who were on relatively low doses of bromocriptine can be safely switched to piribedil based on a conversion ratio of either 1:5 or 1:10. However, the higher conversion ratio has to be carried out with caution in patients with daytime somnolence.
Tan
E K
EK
Department of Neurology, Singapore General Hospital, National Neuroscience Institute Sing Health, Singapore.
Ratnagopal
P
P
Han
S Y
SY
Wong
M C
MC
D000284:Administration, Oral; D000368:Aged; D000978:Antiparkinson Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D001971:Bromocriptine / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D018592:Cross-Over Studies; D005260:Female; D006212:Hallucinations / Q000139:chemically induced; D006801:Humans; D008297:Male; D008875:Middle Aged; D009325:Nausea / Q000139:chemically induced; D010300:Parkinson Disease / Q000188:drug therapy* / Q000473:pathology; D010891:Piribedil / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D011595:Psychomotor Agitation / Q000209:etiology; D012720:Severity of Illness Index; D016037:Single-Blind Method; D012893:Sleep Wake Disorders / Q000139:chemically induced; D016896:Treatment Outcome
D000978:Antiparkinson Agents; D001971:Bromocriptine; D010891:Piribedil