A 67 year old male with postherpetic neuralgia complained of right anterior chest throbbing pain and also allodynia. We performed thoracic epidural block with 0.25% bupivacaine and 1% lidocaine. Oral carbamazepine and imipramine were also administred concomitantly. One month later, patient complained of fatigue, anorexia, pruritis, jaundice, and dark urine. Liver function test values were significantly elevated then. Therefore we removed the epidural catheter and ceased all medication. Liver function test values decreased rapidly after discontinuation of medication. Hepatitis might have developed as result of drugs administered and could have been prevented if the patient had been monitored with regular clinical laboratory follow up. The purpose of this case report is emphasize the importance of early regular laboratory test to detect any possible side effect that may occur by administration of drugs during treatment of chronic pain.