To the Editor.—We read with interest the article by Roti et al1 regarding the use of a calcium-channel blocker, diltiazem, for the treatment of tachyarrhythmias in hyperthyroid patients. The authors suggest that calcium channel antagonists may be useful when β-blockers are contraindicated, as in asthmatics, or as a possible adjunct to β-blockers in the treatment of thyrotoxicosis. Unfortunately, as the authors suggest, they did not compare the effect of diltiazem with β-blockers nor take into consideration the possibility of a placebo effect.
We completed a randomized, cross-over, double-blind, pilot study2 comparing the clinical effects of diltiazem (60 mg, orally, four times a day for 1 week) with propranolol (40 mg, orally, four times a day for 1 week) therapy in six newly diagnosed thyrotoxic patients. We found both drugs to be strongly effective in controlling symptoms (18 symptoms were graded) and in improving clinical signs of thyrotoxicosis.