According to ACLS guidelines, the first drug of choice in stable tachycardia with a narrow QRS complex is adenosine, given as a rapid IV push of 6 mg followed by a normal saline flush. If the rhythm is regular and monomorphic, adenosine may also be considered for unstable patients before synchronized cardioversion. Expert consultation should be strongly considered for stable wide QRS complex tachycardia, and antiarrhythmic infusions such as procainamide, amiodarone, or sotalol IV may be used.