Pramipexole enhances analgesic properties of low-dose morphine for acute pain

Use of the dopamine 3 receptor agonist pramipexole (PPX) as adjuvant therapy appears to facilitate the reduction of patient exposure to opioids and its associated risks, according to a study.

A team of investigators conducted a double-blinded, randomized, noninferiority study, reviewed and approved by the University and Medical Center Institutional Review Boards, to show that low-dose morphine administered in conjunction with PPX was not inferior to a standard dose in providing analgesia for acute pain.

Participants were randomly assigned to receive either intravenous morphine 0.1 mg/kg plus a placebo pill or morphine at 0.05 mg/kg plus a 0.25-mg PPX pill. Using visual analogue (VAS) and numeric rating scales (NRS), pain scores were measured before and at 15-min intervals after treatment for 120 min.

Clinically significant reduction in pain score (defined as ≥50-percent decrease) and the need for rescue medication within 30 min of drug administration were the primary outcomes.

The investigators examined the trends in pain ratings across time using locally weighted smoothing scatter plot-smoothing curves. They also analysed the difference in the proportion of patients achieving at least 50-percent improvement in pain at 120 min with a noninferiority margin of ‒0.20 between groups.

Eighteen patients completed the study. Patients in both groups demonstrated a similar decrease in VAS and NRS scores. This finding indicated the comparable analgesia achieved in the combination group, but with only one-half the dose of morphine.

Of note, one patient in the morphine alone group needed rescue medication for pain.

“Managing the complex risk-benefit profile of opioid therapeutics is a significant challenge,” the investigators said. “Current guidelines call for minimizing opioid doses in cases where opioids are required.”