Analgesic efficacy of tramadol, pregabalin and ibuprofen in menthol-evoked cold hyperalgesia

Abstract 

We investigated the analgesic efficacy of single doses of ibuprofen, tramadol and pregabalin in menthol-evoked cold pain in a randomized, placebo-controlled four-way cross-over study in 20 healthy volunteers. Tramadol 100mg significantly reduced menthol-evoked cold hyperalgesia. Effects of ibuprofen 600mg and pregabalin 100mg were not significant. Analgesic effects of tramadol were associated with minor side effects, particularly fatigue and nausea. Minor side effects also accompanied analgesic effects of pregabalin and ibuprofen in subjects responding to these drugs, mostly fatigue, dizziness and difficulties to concentrate for pregabalin and gastric upset for ibuprofen. Five out of 18 subjects had a ⩾50% reduction of cold hyperalgesia with tramadol, three of these additionally responded to pregabalin, and two with all three drugs. The numbers needed to treat (NNT⩾50% for tramadol 4.5, for pregabalin 9) largely agree with the reported efficacy of tramadol and of moderate dosages of pregabalin in patients with peripheral or central neuropathic pain suggesting that menthol-evoked cold pain hypersensitivity may represent a valid model for neuropathic pain, particularly cold allodynia.

Keywords: Cold allodynia, Experimental pain, Opioids, Non-steroidal anti-inflammatory drugs, Ca²⁺ channel alpha2delta ligands, Menthol