Treatment considerations for patients with neuropathic pain and other medical comorbidities.

The efficacy of drugs for neuropathic pain has been established in randomized controlled trials that have excluded patients with comorbid conditions and those taking complex medications. However, patients with neuropathic pain frequently present with complex histories, making direct application of this evidence problematic. Treatment of neuropathic pain needs to be individualized according to the cause of the pain, concomitant diseases, medications, and other individual factors. Tricyclic antidepressants (TCAs), gabapentinoids, selective noradrenergic reuptake inhibitors, and topical lidocaine are the first-line choices; if needed, combination therapy may be used. When a new drug is added, screening for potential drug interactions is recommended. The TCAs have anticholinergic adverse effects and may cause orthostatic hypotension. They should be avoided or used cautiously in patients with cardiac conduction disturbances or arrhythmias. Patients who lack cytochrome P450 2D6 isoenzyme activity are prone to adverse effects of TCAs and venlafaxine and have a weaker analgesic response to tramadol. A combination of several serotoninergic drugs may lead to serotonin syndrome. Risk of gastrointestinal tract bleeding is increased in patients taking selective serotonin reuptake inhibitors or venlafaxine, especially when combined with nonsteroidal anti-inflammatory drugs. Dose adjustment may be needed in patients with renal or hepatic impairment. Depending on the drug, the dose is reduced or the dosage interval lengthened. Slow titration and careful follow-up are needed. No drug is absolutely safe during pregnancy and lactation. Particular care must be exercised during the first trimester when drug dose should be as low as possible. Individual weighing of benefits and risks should guide therapeutic decisions.