Effects of a Dopamine Agonist on Pharmacodynamics of Levodopa in Parkinson's Disease
Effects of a Dopamine Agonist on Pharmacodynamics of Levodopa in Parkinson's Disease
The purpose of this study is to determine whether there is a benefit to giving a dopamine
 agonist to a patient with Parkinson's disease who is already being treated with levodopa.
Patients with idiopathic PD based on London Brain Bank criteria as determined by an OHSU
 movement disorder specialist entered the study. They gave informed consent to a protocol
 approved by the Oregon Health and Science University Institutional Review Board and General
 Clinical Research Center (GCRC) Review Committee.

 Patients were on long-term levodopa therapy, and had motor fluctuations and dyskinesia as
 determined during screening. Subjects were screened with finger tapping (FT) in the
 practically defined OFF motor state, having been off LD overnight, and in the practically
 defined ON motor state. To qualify, they had to have a minimum 10% improvement in the ON
 state.

 The trial was a randomized, double-blind, placebo-controlled crossover study with subjects on
 pramipexole for 4 weeks and an identically appearing placebo for 4 weeks. The response to
 two-hour LD infusions at 0.5 (threshold) and 1.0 (suprathreshold) mg/kg/hr were examined at
 the end of each 4 week treatment period.

 The primary outcome was finger-tapping speed, as a surrogate marker of bradykinesia, over a
 seven hour time period. The area under the curve (AUC) was calculated as finger taps x
 minutes (FTM). Secondary outcomes measured included peak motor response, as measured by FT,
 walking speed, dyskinesia, time-to-ON (defined as a 10% increase in finger tapping speed over
 the baseline), and effects of LD infusion on subjects' perceived mood, anxiety and fatigue.

 Subjects were randomized to receive either pramipexole (PPX) or placebo for the initial 5
 weeks of the study. The PPX and placebo was titrated up over 9 days to a target dose of 1.0mg
 TID. If they were already taking a DA, this was tapered and discontinued while the study
 medication was titrated upward. Their LD was continued according to the subjects normal
 schedule during this time period, as well as any other antiparkinsonian medications they were
 taking.

 After a maintenance phase of 4 weeks on study medication (PPX 1.0mg TID or placebo TID)
 subjects were admitted in the evening to the inpatient GCRC at OHSU. Their last LD dose was
 given no later than 10 pm and all other PD medications were withheld after 10 pm. They
 practiced FT sessions on the night of admission. At 7 AM the next morning, a dose of the
 study drug was given and an IV line was placed. An IV levodopa infusion was administered
 starting at 9 am, continuously over 2 hours at a rate of either 0.5mg/kg/hr or 1.0 mg/kg/hr.
 The infusion rate was blinded and randomized. The infusion was stopped at 11 am. After 2:00
 PM and when subjects were deemed "off", the usual antiparkinson medications were
 reinstituted.

 FT, tremor, walking (timed and # of steps), dyskinesia, and a "global" PD scale were measured
 by research nurses, and subjects completed visual analogue scales (VASs) for anxiety, fatigue
 and mood every 30 minutes from 7:00 AM until 2:00 PM.
Inclusion Criteria:

 -  Age 30-80

 -  Idiopathic PD Hoehn & Yahr stage 2-4,

 -  diagnosed by 2 of the 3 cardinal motor features

 -  Fluctuation response to levodopa

 -  Dyskinesia

 -  No other historical, laboratory or physical signs to suggest an alternate diagnosis

 -  No significant dementia, MMSE>24

 -  On oral levodopa therapy

 Exclusion Criteria:

 -  dementia

 -  psychosis

 -  severe anxiety

 -  unstable cardiovascular disease

 -  uncontrolled hypertension

 -  history of cardiac arrhythmias

 -  active peptic ulcer disease

 -  anemia (HCT<32%)