Journal Article

The effects of a dopamine agonist (apomorphine) on experimental and spontaneous pain in patients with chronic radicular pain: A randomized, double-blind, placebo-controlled, cross-over study

Pud, Dorit, Eisenberg, Elon, Treister, Roi, Suzan, Erica, Haddad, May

2018

Overview

Although evidence suggests that dopaminergic systems are involved in pain processing, the effects of dopaminergic interventions on pain remains questionable. This randomized, double blinded, placebo-controlled, cross-over study was aimed at exploring the effect of the dopamine agonist apomorphine on experimental pain evoked by cold stimulation and on spontaneous pain in patients with lumbar radicular (neuropathic) pain. Data was collected from 35 patients with chronic lumbar radiculopathy (18 men, mean age 56.2±13 years). The following parameters were evaluated before (baseline) and 30, 75 and 120 minutes subsequent to a subcutaneous injection of 1.5 mg apomorphine or placebo: cold pain threshold and tolerance in the painful site (ice pack, affected leg) and in a remote non-painful site (12°C water bath, hand), and spontaneous (affected leg) pain intensity (NPS, 0-100). One-hundred and twenty minutes following apomorphine (but not placebo) injection, cold pain threshold and tolerance in the hand increased significantly compared to baseline (from a median of 8.0 seconds (IQR = 5.0) to 10 seconds (IQR = 9.0), p = 0.001 and from a median of 19.5 seconds (IQR = 30.2) to 27.0 seconds (IQR = 37.5), p<0.001, respectively). In addition, apomorphine prolonged cold pain tolerance but not threshold in the painful site (from a median of 43.0 seconds (IQR = 63.0) at baseline to 51.0 seconds (IQR = 78.0) at 120 min, p = 0.02). Apomorphine demonstrated no superiority over placebo in reducing spontaneous pain intensity. These findings are in line with previous results in healthy subjects, showing that apomorphine increases the ability to tolerate cold pain and therefore suggesting that dopaminergic interventions can have potential clinical relevance.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Adult / Aged / Agonists / Analgesics / Analgesics, Opioid - therapeutic use / Analysis / Apomorphine / Apomorphine - metabolism / Apomorphine - pharmacology / Apomorphine - therapeutic use / Biology and Life Sciences / Chronic pain / Chronic Pain - drug therapy / Clinical trials / Cold / Cold tolerance / Cross-Over Studies / Diabetic neuropathy / Dopamine / Dopamine - pharmacology / Dopamine Agonists - metabolism / Dopamine receptors / Dosage and administration / Double-Blind Method / Double-blind studies / Drug therapy / Drug Tolerance / Female / Fibromyalgia / Health sciences / Healthy Volunteers / Humans / Hypotheses / Injection / Leg / Lumbosacral Region / Male / Medical imaging / Medicine and Health Sciences / Middle Aged / Neuralgia / Neuralgia - drug therapy / Neuropathy / Neurosciences / Pain / Pain - drug therapy / Pain management / Pain Measurement / Pain perception / Pain Threshold - drug effects / Parkinson's disease / Patients / Physical Sciences / Placebos / Radiculopathy - drug therapy / Randomization / Registration / Social Sciences