Carbamazepine for acute and chronic pain

Background: Anticonvulsant drugs have been used in the management of pain since the 1960s. The clinical impression is that they are useful for chronic neuropathic pain, especially when the pain is lancinating or burning. Objectives: To evaluate the analgesic effectiveness and adverse effects of the anticonvulsant medicine carbamazepine for pain management in clinical practice and to identify a clinical research agenda. Migraine and headache studies are not included in this review. Search strategy: Randomised trials (RCTs) of anticonvulsants in acute, chronic or cancer pain were identified by MEDLINE (1966-2004), EMBASE (1994- 2004), SIGLE (1980-2004) and the Cochrane Controlled Trials Register (CENTRAL/CCTR) (Cochrane Library Issue 3, 2003). In addition, 41 medical journals were hand searched for a previous version of this review. Additional reports were identified from the reference list of the retrieved papers, and by contacting investigators. Date of most recent search: November 2004. Selection criteria: Randomised trials reporting the analgesic effects of carbamazepine in patients, with subjective pain assessment as either the primary or a secondary outcome. Data collection and analysis: Data were extracted by two independent reviewers, and trials were quality scored. Numbers-needed-to-treat (NNTs) were calculated from dichotomous data for effectiveness, adverse effects and drug-related study withdrawal, for individual studies and for pooled data. Main results: Twelve studies were included (404 participants). Four studies included trigeminal neuralgia patients. Two studies which provided evaluable data yielded an NNT for effectiveness of 1.8 (95% CI 1.4-2.8). For diabetic neuropathy there was insufficient data for an NNT to be calculated. Numbers-needed-to-harm (NNHs) were calculated where possible by combining studies for each drug entity irrespective of the condition treated. The results were, for minor harm, carbamazepine 3.7 (CI 2.4-7.8), NNHs for major harm were not statistically significant for carbamazepine compared with placebo. There is no evidence that carbamazepine is effective for acute pain. Authors' conclusions: There is evidence to show that carbamazepine is effective but trials are small. SYNOPSIS Carbamazepine, an anticonvulsant medicine, is effective for relieving pain caused by damage to nerves, either from injury or disease. Anticonvulsants are a group of medicines commonly used for treating fits' or epilepsy, but which are also effective for treating pain. The type of pain which responds well is neuropathic pain, e. g., postherpetic neuralgia (persistent pain experienced in an area previously affected by shingles), trigeminal neuralgia and painful complications of diabetes. Approximately two-thirds of patients who take carbamazepine for neuropathic pain can be expected to achieve good pain relief.