Cardiology | Antiarrhythmic Drug Guide | Class IV | Verapamil

Verapamil

IV Dose 0.075-0.150 mg/kg (max 10 mg) over 1-2 minutes.
Oral dose 4-17 mg/kg/day divided q 8 hours (BID or QD with slow release form)
Levels 0.1-0.3 ug/ml.
Kinetics Zero-order (half-life related to dose). Extensive first-pass metabolism. Elimination half-life 12 hours on chronic oral therapy, but 6 hours after single dose.
Cautions Do not use under 12 months of age, especially under 3 months, hypotension, CV collapse, death). Use with caution long-term in patients with manifest preexcitation. (conversion of SVT is OK). Do not pre-treat with calcium chloride, as it interferes with the therapeutic effect. Be prepared with calcium, fluids and dopamine if hypotension occurs following administration.
Interactions Contraindicated with beta blockers, due to synergistic negative inotropy. Contraindicated with quinidine, due to synergistic negative inotropy. Increases digoxin levels 40-75% (quinidine-like). Therapeutic effect blocked by anticholinergic properties of disopyramide
Preparations Calan scored tablets: 80, 120 mg. Calan SR scored tablets: 240 mg. Calan injection: 5 mg/2 ml, 10 mg/4 ml amps, vials. Isoptin: same Verelan pellet-filled capsules: 120, 240 mg. (QD dosing)
FDA approval in children no

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