Topical capsaicin as effective as oral agents for pain relief in PDPN
The high-concentration capsaicin patch shows promise in the management of painful diabetic peripheral neuropathy (PDPN), with an effect that is similar to that observed with oral agents but offering systemic tolerability benefits, according to a network meta-analysis.
Researchers searched multiple electronic databases for randomized controlled trials assessing the efficacy and safety of ≥4 weeks treatment with capsaicin 8% patch vs oral, centrally acting agents (ie, pregabalin, gabapentin, duloxetine, amitriptyline) in patients with PDPN.
Efficacy outcomes were the proportions of patients with ≥30 and ≥50 percent reductions in pain. Tolerability outcomes included somnolence, dizziness, nausea, diarrhoea, constipation, headache, fatigue, insomnia and rate of discontinuation due to adverse events (AEs).
A Bayesian method was applied to analyse aggregate-level data, and fixed and random effects models were estimated.
Pooled data from 25 randomized controlled trials showed that the capsaicin patch was superior to placebo with respect to ≥30 percent pain reduction (odds ratio [OR], 2.28; 95 percent CI, 1.19 to 4.03). The patch also demonstrated a numerical advantage compared with pregabalin (OR, 1.83; 0.91 to 3.34) and gabapentin (OR, 1.66; 0.74 to 3.23), and had similar efficacy compared with duloxetine (OR, 0.99; 0.5 to 1.79). There was not enough evidence to assess the relative efficacy of amitriptyline. For the more stringent outcome of ≥50 percent pain reduction, the patch showed a numerical advantage vs placebo but similar efficacy vs oral agents.
For tolerability, the capsaicin patch was only evaluated for headache as the incidence for other outcomes was 0 percent. On the other hand, oral, centrally acting agents had a significantly increased risk of somnolence (pregabalin, gabapentin, duloxetine and amitriptyline), dizziness (pregabalin, gabapentin, duloxetine and amitriptyline), nausea (duloxetine), diarrhoea (duloxetine), fatigue (duloxetine) and discontinuation because of AEs (pregabalin, gabapentin and duloxetine) as compared with placebo. Duloxetine, relative to pregabalin and gabapentin, had a significantly lower risk of dizziness but a significantly higher risk of nausea.
The present network meta-analysis provides insight into the relative efficacy of the capsaicin 8% patch vs oral, centrally acting agents recommended by the National Institute For Health and Clinical Excellence in UK (ie, pregabalin, duloxetine, gabapentin) in the treatment of patients with PDPN, researchers said. Findings suggest that the patch is as effective as duloxetine—which is recommended as a treatment of choice for PDPN in most clinical guidelines—in terms of delivering pain relief.