Antiepileptics commonly used for neuropathic pain
A multitude of antiepileptic drugs exist that are useful in treatment of neuropathic pain. They work by various mechanisms including effects on sodium or calcium conduction, increase in gamma-aminobutyric acid (GABA) levels, reduction in glutamate levels, or other unknown mechanisms. Gabapentin is an alpha-2 delta calcium channel ligand and has been shown to significantly reduce pain in DPN and PHN, and has a favorable side-effect profile compared to first-generation anticonvulsants. There are two longer acting forms of gabapentin, once daily gastroretentive gabapentin and a twice daily prodrug, pregabalin. Pregabalin is similar to gabapentin by binding at the same site on voltage-dependent calcium channels, and both drugs have similar side effects of dizziness and sedation and require dose adjustments in renal insufficiency. Controlled trials reveal carbamazepine to be effective in trigeminal neuralgia and DPN, but not in PHN or central pain. Oxcarbazepine and sodium valproate also have benefit in DPN. Topiramate, levetiracetam, phenytoin, lamotrigine, and the newer antiepileptic lacosamide, among others, have all been considered in treatment, though they have limited data supporting their efficacy. Eventual choice in antiepileptic should be based on side effect profile and trial and error.