Pharmaceutical company Sanofi-Synthelabo announced Monday that it was halting the clinical trial of the heart arrhythmia medication dronedarone due to safety concerns. According to the drug maker, 24 patients died while taking dronedarone, compared to 10 in the placebo group. Sanofi was attempting to develop a safer version of its Cordarone drug, an antiarrhythmic medication linked to sometimes fatal pulmonary toxicity, abnormal liver function tests, hypothyroidism and optic neuropathy. A spokesperson for Sanofi said the company might attempt another trial of dronedarone in one to two years after the current study's procedures are modified.