The effect of haloperidol administration on relieving cluster headache, probable role of dopaminergic pathway; a double blind clinical trial

Background: The present study was carried out with the aim of assessing the effectiveness of 2.5 mg dose of haloperidol compared with its standard 5 mg dose in relieving symptoms of cluster headaches and finding out to what extent the dopaminergic pathway affects the incidence of cluster headaches. Methods: The present study is a double-blind randomized clinical trial carried out in 3 health centers, Tehran, Iran. Patients diagnosed with cluster headache were treated by intravenous administration of 2.5 and 5 mg of haloperidol. Using a standard visual analog scale, pain severity was recorded before and 30, 60, 90, and 120 minutes after intervention. Treatment success (at least 3 points decrease in pain severity), side effects and recurrence of the headache were evaluated. Results: Finally, 42 patients were treated with 2.5 mg dose of haloperidol and 41 were in the 5 mg dose haloperidol treatment group. 40 (95.2%) patients who were treated with 2.5 mg dose of haloperidol experienced a significant decrease in pain (at least 3 points decrease in pain severity) in the initial 30 minutes. During this time, all of the patients (success rate=100%) treated with 5 mg dose of the drug had a significant decrease in pain. The two doses did not have a significant difference regarding treatment success (p=0.42). Conclusion: Results of the present study showed that both 2.5 and 5 mg doses of haloperidol have similar effectiveness in reducing cluster headaches. The high success rate observed indicates that hyperactivity of dopaminergic pathway plays an important role in onset of cluster headaches.