Pharmacological treatment of tremor in multiple sclerosis; a systematic review.

Background: Tremor is a relatively common symptom in Multiple Sclerosis (MS). It can negatively affect several aspects of the patients' life and is one of the most disabling symptoms in MS. Pharmacological treatment of MS-related tremor was studied for several years, though treatment is still challenging. This study will review all studies on the pharmacological treatment of tremor in MS and update the treatment recommendations. Methods: Any relevant English-language clinical trial that investigated the pharmacological treatment of MS-related tremor in adults was eligible in this study. We searched Medline (PubMed), Scopus, EMBASE, and Web of Science. Bias assessment was performed by the CASP (Critical Appraisal Skills Programme) checklist. All methods followed PRISMA guidelines. Results: The initial search resulted in 3024 articles; 26 articles were included as eligible studies, 13 articles had a low risk of bias, and remained for full manuscript review. The results of studies on 5-HT3 receptor antagonists as a single dose treatment were inconsistent. Botulinum toxin A had significant effects on MS-related tremor, but adverse effects and injection procedures limited its application. The application of cannabis-based medicine to treat MS-related tremor could not be recommended due to inconclusive therapeutic effects and several side effects. Levetiracetam had inconsistent results, and other anti-epileptic drugs were not studied precisely. Isoniazid has minor therapeutic effects and possible adverse effects in the treatment of MS-related tremor. Conclusion: Further well-designed comparative clinical trials with a large sample size can improve clinical management of tremor in patients with MS.