Procainamide (Procaine amide) is a specific and potent inhibitor of DNA methyltransferase 1 (DNMT1), which reactivates the expression of tumor suppressor factors by demethylating tumor suppressor genes. Procainamide induces vacuolization in various cell types and reduces cell proliferation and migration. Procainamide relaxes airway smooth muscle by activating potassium channels. Procainamide can be used in cancer and arrhythmia research.