Tricyclic antidepressants, especially clomipramine and amitriptyline, have been shown to improve pain in what appears to be a central manner.[citation needed] Nefopam is used in Europe for pain relief with concurrent opioids. The exact mechanism of carbamazepine, gabapentin, and pregabalin is similarly unclear, but these anticonvulsants are used to treat neuropathic pain with differing degrees of success. Anticonvulsants are most commonly used for neuropathic pain as their mechanism of action tends to inhibit pain sensation.[16]