D,L-Propranolol and D-propranolol in essential tremor
The β-adrenoceptor antagonist D,L-propranolol is the drug of first choice in the symptomatic control of essential tremor (ET) but the mechanism that mediates the tremolytic effect has not been established. Some authors believe that the drug exerts its effect mainly by blocking central and/or peripheral β-adrenergic receptors (Young et al., 1975; Jefferson et al., 1979), but other mechanisms of action unrelated to blockade of β-adrenoceptors have also been postulated (Young et al., 1975; Koch-Weser, 1975). In particular, the possible role of the membrane-stabilising action (MSA) (quinidine-like) is unclear. While an early report claimed that D-propranolol (the D-isomer retaining the MSA of the racemic mixture but virtually devoid of β-adrenoceptor blocking properties) is as effective as D,L-propranolol (McClure and Davis, 1976), a more recent study failed to confirm these findings (Teräväinen and Larsen, 1981). In a previous study (Calzetti et al., 1983) we have demonstrated that a single oral dose of D,L-propranolol (120 mg) significantly reduces the amplitude of ET within 2 h following its administration. The present study was designed to assess under controlled conditions the comparative tremolytic efficacy of D-propranolol and D,L-propranolol on acute administration.
KeywordsPlacebo Fatigue Depression Caffeinated Neurol
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