Metoprolol and alpha-hydroxymetoprolol concentrations and reduction in essential tremor

The relationship between reductions in essential tremor and concentrations of metoprolol and alpha-hydroxymetoprolol was examined in five patients with essential tremor after treatment with 0, 25, 50, and 75 mg metoprolol twice daily for 7 to 10 days. Serum concentrations of metoprolol and alpha-hydroxymetoprolol were measured simultaneous to serial accelerometry measurements of tremor over 8-hr periods. There was a relationship between degree of tremor reduction and steady-state metoprolol concentration. Time course of the drug and metabolite concentration correlated better with the time course of effect than with the time course of metoprolol concentration alone. Data suggest that the alpha-hydroxymetabolite of metoprolol may contribute to the reduction in essential tremor.