Treatment of post-herpetic pain in myasthenia gravis: exacerbation of weakness due to gabapentin.

Here, we present a case of a 64-year-old female suffering from a severe form of antibody-positive myasthenia gravis. Under an immunosuppressive regimen with cyclosporine A, she experienced an episode of thoracic herpes zoster followed by intense post-herpetic neuralgia. In order to avoid drug interactions as well as adverse effects of carbamazepine in myasthenia gravis, gabapentin was chosen for the treatment of neuropathic pain. Within a few days she noticed increasing weakness, but continued medication for 8 weeks as gabapentin was not identified as the hazardous agent by her physician. Acetylcholine receptor antibody levels remained unchanged, but increased decrement was observed clinically and in repetitive nerve stimulation. After withdrawal of gabapentin, she recovered quickly to her previous condition.