Treatment with the anticonvulsant agent pregabalin was superior to placebo for reducing neuropathic pain in patients with chronic spinal cord injury (SCI), while cannabinoids were ineffective, according to a study in Pain Medicine.
The study was a systematic review and meta-analysis of 21 studies that examined the efficacy of several different drug classes used in the treatment of chronic SCI pain. In all, 17 studies were included in the meta-analysis to examine the rate of adverse events with these drug classes.
A total of 6 studies reported data for anticonvulsants, 3 studies focused on antidepressants, 8 examined analgesics, 2 investigated antispasticity agents, 1 study looked into the pain-reducing effects of cannabinoids, and 2 other studies examined other therapies.
The pooled analysis included 877 patients with chronic SCI-related pain. Their ages ranged between 18 and 80 years. The most frequently reported adverse events across studies were dizziness, dry mouth, nausea, and constipation.
In the meta-analysis, the point estimate for difference between pregabalin and placebo was -0.79 (95% CI, -1.1 to -0.46), which was in favor of pregabalin. However, patients who were prescribed pregabalin were 3.15 times more likely to experience somnolence (95% CI, 2.00-4.98) and 2.9 times more likely to develop dizziness (95% CI, 1.58-5.30) than those using a placebo.
Treatment with ketamine was associated with a higher risk of reduced vision (RR, 9.00; 95% CI, 0.05-146.11), dizziness (RR, 8.33; 95% CI, 1.73-40.10), and somnolence (RR, 7.00; 95% CI, 1.73-40.1).
Withdrawal rates included 18.4% for antidepressants, 0% to 30% for anticonvulsants, 0% to 10% for antispasticity agents, 0% to 48% for analgesics, 28.6% for cannabinoids, and 0% to 22.2% for other medications.
Limitations of this meta-analysis were the small sample sizes of some of the studies as well as the inclusion of only those articles that were written in English.
The researchers wrote that the increased “incidence of somnolence” with pregabalin “could be attributed to increased sleep disturbance related to other injury related symptoms such as pain, spasticity, incontinence, and mood disorders which are frequently observed in the SCI population.”
Canavan C, Inoue T, McMahon S, Doody C, Blake C, Fullen BM. The efficacy, adverse events and withdrawal rates of the pharmacological management of chronic spinal cord injury pain: a systematic review and meta-analysis. Pain Med. Published online April 12, 2021. doi:10.1093/pm/pnab140