Example: A patient was admitted to the hospital because of an acute attack of myocardial ischemia. After stabilizing his condition, the patient suffered from repeate episodes of ventricular tachycardia and he was started on lidocaine. Recommend an iv loading dose and a constant rate iv infusion to achieve steady state lidocaine conc of 4 mg/L. (lidocaine Vc = 35 L, Vdβ = 150 L, and CLT = 50 L/hr)
This infusion rate can be calculated from:
The loading dose based on an average value for Vd between Vc and Vdβ (e.g. 60 L)
The loading dose based on Vc followed by administration of small iv bolus doses (50 mg) after 0.25, 0.5, and 1.0 hr of starting the infusion.
- Loading dose of 240 mg iv
- Or a loading dose of 140 mg followed by small is boluses (50 mg) after 0.25, 0.5, and 1 hr to compensate for the decrease in drug conc due to drug distribution.
