Maintenance infusion is 1 4 mg/min although one could start at 0.5 mg/min VT, VF INa No marked effect on most intervals; QTc can slightly shorten terminal 90 120 min. Prolonged in HF, liver disease, shock, severe renal disease Metab: H Excr: U Cardiac: Bradycardia, hemodynamic collapse, AVB, sinus arrest Other: Delirium, psychosis, seizure, nausea, tinnitus, dyspnea, bronchospasm (Continued) CLINICAL STATEMENTS AND GUIDELINES Metoprolol (II) IV: 5 mg q 5 min up to PO: 25 100 mg Extended release qd or q 12 h VT, PVC Beta 1 receptor Sinus rate slowed AV nodal refractoriness increased : 3 4 h Metab: H Excr: U Cardiac: Bradycardia, hypotension, AVB Other: Dizziness, fatigue, diarrhea, depression, dyspnea Mexiletine (IB) PO: 150 300 mg q 8 h or q 12 h T, VF, PVC, has a role in patients INa No marked effect on most intervals; QTc can slightly shorten : 10 14 h Metab: H Excr: U Cardiac: HF, AVB Other: Lightheaded, tremor, ataxia, paresthesias, nausea, blood dyscrasias Nadolol (II) PO: 40 320 mg daily VT, PVC, LQTS, CPVT Beta 1 and 2 receptors Sinus rate slowed AV nodal refractoriness increased : 20 24 h Metab: none Excr: U Cardiac: Bradycardia, hypotension, HF, AVB Other: Edema, dizziness, cold extremities, bronchospasm Procainamide (IA) IV: loading dose 10 17 mg/kg at 20 50 mg/ min Maintenance dose: 1 4 mg/min PO (SR preparation): 500 1250 mg q 6 h VT INa , IKr QRS prolonged QTc prolonged; increased DFT Metab: H : 2 5 h; NAPA 6 8 h prolonged in renal dysfunction. 