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Sodium Channel Blockade May Contribute to the Analgesic Efficacy of Antidepressants

2006; Elsevier BV; Volume: 8; Issue: 4 Linguagem: Inglês

10.1016/j.jpain.2006.10.001

1528-8447

Ivy E. Dick, Richard M. Brochu, Yamini Purohit, Gregory J. Kaczorowski, William J. Martin, Birgit T. Priest,

Pharmacological Effects of Natural Compounds

Sodium channel blockers such as lidocaine, lamotrigine, and carbamazepine can be effective in the treatment of neuropathic pain. Though not approved for neuropathic pain indications, tricyclic antidepressants are often considered first-line treatment for conditions such as post-herpetic neuralgia and diabetic neuropathy. Several tricyclic antidepressants have been shown to block peripheral nerve sodium channels, which may contribute to their antihyperalgesic efficacy. In this study, we compared the sodium channel–blocking potency of a number of antidepressants, including tricyclic antidepressants and selective serotonin reuptake inhibitors. All compounds tested inhibited NaV1.7 in a state- and use-dependent manner, with affinities for the inactivated state ranging from 0.24 μmol/L for amitriptyline to 11.6 μmol/L for zimelidine. The tricyclic antidepressants were more potent blockers of NaV1.7. Moreover, IC50s for block of the inactivated state for amitriptyline, nortriptyline, imipramine, desipramine, and maprotiline were in the range of therapeutic plasma concentrations for both the treatment of depression as well as neuropathic pain. By contrast, fluoxetine, paroxetine, mianserine, and zimelidine had IC50s for NaV1.7 outside their therapeutic concentration ranges and generally were not efficacious against post-herpetic neuralgia or diabetic neuropathy. These results suggest that block of peripheral nerve sodium channels may contribute to the antihyperalgesic efficacy of certain antidepressants.PerspectiveTricyclic antidepressants are often considered first-line treatment for neuropathic pain. Some tricyclic antidepressants block sodium channels, which may contribute to their antihyperalgesic efficacy. In the current study, we compared the potency of peripheral sodium channel blockade for several tricyclic antidepressants and selective serotonin reuptake inhibitors with their therapeutic efficacy.