When will you use lidocaine versus adenosine?

Cardiac arrhythmias?: I assume you're asking about cardiac arrhythmias? Lidocaine affects ventricular ectopy and has no effect on av conduction. It's was used for ventricular tachycardia and has largely been supplanted by amiodarone. Adenosine has no effect on the ventricles. It blocks av conduction. It's used to terminate supraventricular tachycardias.