An update on pharmacotherapy for trigeminal neuralgia

IntroductionTrigeminal neuralgia is a rare condition that can be effectively treated by carbamazepine or oxcarbazepine but these older drugs are associated with dose-dependent and potentially treatment-limiting adverse effects. Third-generation anticonvulsants, new calcitonin gene-related peptide blockers for migraine, and older drugs such as ketamine and cannabinoids may be promising adjuvants or monotherapeutic options.Areas CoveredThe new drugs, their presumed mechanisms of action, safety and efficacy are discussed herein. There is a paucity of robust clinical evidence in support of these drugs for trigeminal neuralgia. New migraine agents are considered as well although migraines and trigeminal neuralgia are distinct, albeit similar, conditions. No new drugs have been released to market in recent years with the specific indication of trigeminal neuralgia.Expert opinionIn real-world clinical practice, about half of trigeminal neuralgia patients take more than one agent for prevention and combination therapy may be the optimal approach. Combination therapy might allow for lower doses of carbamazepine or oxcarbazepine, thus reducing the number and severity of potential adverse events but the potential for pharmacokinetic drug-drug interactions must be considered. Drug therapy for trigeminal neuralgia involves acute or abortive treatments, often administered in hospital versus long-term preventive therapy, usually involving oral agents. Trigeminal neuralgia is a relatively rare condition that usually affects one side of the face below the eye around the cheekbone. The cause of trigeminal neuralgia is sometimes a damaged nerve or a nerve that has lost part of its outer protective sheath (myelin). However, trigeminal neuralgia may have other neurological causes as well. Pain can be triggered by touch, pressure, or chewing and it tends to occur in very painful brief attacks followed by pauses with little or no pain. There are two types of drug treatment for trigeminal neuralgia: drugs to stop an ongoing attack (which are often administered in an emergency room or hospital intravenously) and drugs that are taken orally over the long term to reduce or prevent attacks.The two most effective drugs for trigeminal neuralgia are carbamazepine and oxcarbazepine, which are actually drugs to prevent seizures. They are effective in reducing the pain intensity and number of attacks of trigeminal neuralgia but they have side effects. In fact, these side effects can be so severe that people stop taking the drugs.Many new drugs have come to market recently that may work for trigeminal neuralgia, although none was specifically developed for this use. The newest generation of anti-seizure medications including eslicarbazepine, lacosamide, levetiracetam, and retigabine, may be just as effective as the older carbamazepine and oxcarbazepine drugs with fewer side effects. Clinical studies are needed to test them in trigeminal neuralgia patients but their mechanisms of action suggest that they might work well.There are some new drugs developed for migraine headache that inhibit a substance in the body called CGRP. Migraine headaches and trigeminal neuralgia have some of the same symptoms but they are different conditions but both involve too much CGRP.Other new drugs include lasmiditan, pimozide (used for Tourette syndrome), tizanidine (muscle relaxant), lamotrigine and vixotrigine (anti-seizure drugs) may also be beneficial. It may be that people with trigeminal neuralgia will have to take combination therapy, the use of two or more drugs with different mechanisms of action. Older drugs like ketamine and cannabinoids are also being considered as possible add-on agents for therapy for trigeminal neuralgia.