Q: While administrating Procainamide, what is the cut off point to stop it depending on EKG criteria?

Answer: The QRS complex widens by 50% or more

Procainamide has a prolong action on cardiac muscles, particularly due to its metabolite N-acetylprocainamide (NAPA), which is also approximately equipotent with the parent drug as an antiarrhythmic agent. But to be of notice, NAPA has an elimination half-life about twice that of procainamide.

Procainamide should be discontinued when

• dysrhythmia is suppressed, or
• if hypotension ensues, or
• the QRS complex widens by 50% or more, or 
• the maximum dose is achieved.