Background and purpose: Vertigo is one of the most common principal complaints of patients in emergency departments. Therefore, this study investigated the effect of Diazepam as benzodiazepine and Promethazine in patients with acute peripheral vertigo.

Materials and methods: A double blind randomized clinical trial was done in which 150 patients were randomly divided into two groups (n=75 per group) to receive either 5mg IV injection of Diazepam (group A) or 25mg IV injection of promethazine (group B). The severity of vertigo was scored before treatment and within four hours after receiving the drugs.

Results: Excellent improvements were seen in 71 (94.7%) patients receiving promethazine while good improvements were observed in 13 (17.3%) patients receiving Diazepam. The mean VAS score was 9.69 before the intervention. While the mean scores for VAS1 (30 minutes after treatment), VAS2 (after two hours), and VAS3 (after four hours) were 7.14, 5.06, and 2.45, respectively. The results showed a reduction over time in both groups in VAS score. The Fisher’s exact test showed significant difference in efficacy of promethazine between the two groups. (P<0.001).

Conclusion: According to this result, promethazine improved peripheral vertigo better than Diazepam. So, it could be used in patients with acute peripheral vertigo.