Best drugs for essential tremor

The two drugs with the best evidence are propranolol and primidone, but the evidence is old, small, and short.

The 2019 BMJ review names propranolol and primidone as first-line drugs for essential tremor [7]. Propranolol is started at 10 mg three times a day and can go up to 360 mg daily. Primidone starts at 25 mg per day. A 1989 study of 50 patients found both drugs reduced tremor scores from about 2.3 at baseline to about 1.2 at one month, with benefit partly fading by six months [5]. A 1987 study found primidone may be more effective in the short term but causes significant acute side effects [1]. A 2002 trial found that starting primidone at a lower dose did not improve tolerability [4].

The mechanism for propranolol involves blocking beta-adrenergic receptors that amplify tremor signals through the cerebellum-thalamus-cortex loop [7]. A 2020 study of 38 patients found 8 weeks of propranolol at 40 mg twice daily reduced SLC1A2 gene expression and lowered tremor scores from 2.7 to 2.1 on the Fahn-Tolosa-Marin scale [3]. That is a real biochemical change but the clinical improvement was modest and the study was not randomized.

What is missing: no long-term safety data beyond 12 months, no head-to-head trial against modern alternatives like topiramate or deep brain stimulation with adequate power, and no study that tracks all-cause outcomes instead of just tremor scores. The BMJ review notes that head and voice tremor show limited chronic response to propranolol [7]. About half of patients respond to alcohol, and those same patients tend to respond to propranolol, suggesting the drug works for a subtype, not everyone [7].

Topiramate is recommended as first-line by some guidelines and second-line by others, with about 30% improvement in some trials [7]. Gabapentin shows mild to moderate tremor reduction not consistently superior to propranolol [7]. Benzodiazepines like alprazolam and clonazepam show some benefit in trials [7]. For severe tremor that does not respond to drugs, deep brain stimulation of the ventral intermediate nucleus or caudal zona incerta produces about 74% tremor reduction at 32 months follow-up [18], and MRI-guided focused ultrasound thalamotomy produces about 62% improvement at two years [7, 11].

My call: propranolol and primidone are the best studied drugs but the evidence is low quality, short-term, and from small trials. For severe tremor, surgical options like DBS or focused ultrasound have stronger evidence of lasting benefit. Confidence: low for drugs, moderate for surgical options.