With the exception of cocaine, all local anesthetics are vasodilators. Patients with preexisting cardiovascular disease may develop heart block and other disturbances of cardiac electrical function at high plasma levels of local anesthetics. Bupivacaine, a racemic mixture of two isomers may produce severe cardiovascular toxicity, including arrhythmias and hypotension. The (S) isomer, levobupivacaine, is less cardiotoxic. Cardiotoxicity has also been reported for ropivacaine when used for peripheral nerve block. The ability of cocaine to block norepinephrine reuptake at sympathetic neuroeffector junctions and the drug's vasoconstricting actions contribute to cardiovascular toxicity. When cocaine is used as a drug of abuse, its cardiovascular toxicity includes severe hypertension with cerebral hemorrhage, cardiac arrhythmias, and myocardial infarction.