Anticonvulsants

The anticonvulsant medications can be divided into first or second-generation agents. The second-generation medications are generally better tolerated and have fewer central nervous system (CNS) side effects than the first generation agents. Of the first generation agents, carbamazepine (Tegretol) has been effective in the treatment of Trigeminal neuralgia. Evidence has also shown moderate efficacy in the treatment of postherpetic neuralgia and diabetic neuropathy. Carbamazepine’s main side effect is sedation. Patients treated with it should also have complete blood counts (CBCs) and liver function tests (LFTs) monitored, as blood dyscrasias and liver abnormalities can occur with the medication. These generally resolve with discontinuation of the drug. The second-generation antiepileptic agents have shown the best documented resolution of neuropathic pain, although the mechanism of action of these drugs remains unknown. Gabapentin (Neurontin) is the first line agent in the treatment of painful diabetic neuropathy and postherpetic neuralgia. Many physicians begin treatment with this agent, mostly because it has been well tolerated, even at high doses. In fact, some evidence shows an anti-anxiolytic effect, and therefore, may be helpful for anxious patients. Unlike carbamazepine, it lacks significant interactions with other drugs. Patients may experience nausea, especially with rapidly increasing doses, or dizziness with higher doses. The FDA recently approved the use of the new anticonvulsant drug, pregabalin (Lyrica), for the treatment of neuropathic pain. It was designed as a more potent successor to gabapentin. Lyrica is also been shown to be effective in the treatment of diabetic neuropathy and post-herpetic neuralgia. This drug can be given less frequently than Gabapentin (twice daily versus three times daily), although it is a Schedule V controlled substance. The FDA also recently approved the use of Lyrica for the treatment of Fibromyalgia, and it is currently the only FDA-approved drug for the treatment of pain associated with Fibromyalgia.