Digoxin is obtained from a plant product and has a half-life of 36 hours. How does this information help us in formulating treatment?
(A) To adjust maintenance dose of digoxin required to keep the blood levels within therapeutic range (B) Intravenous administration in emergency and urgent dosing (C) Long half-life permits altemate day dosing (D) It requires a high loading dose to be administered
(A) Ans: A. To adjust maintenance dose of digoxin required to keep the blood levels within therapeutic range(Ref Goodman Gilman 12/e p33. 37: KDT 7/e p31, 515)Half- life of drug:Determines the maintenance dose of digoxin.Helps maintain therapeutic plasma levels.Maintenance dose also determined by creatinine clearance.Half-life of dioxin:36 to 48 hrs in patients with normal renal function.3.5 to 5 days in anuric patients.In patients with normal renal function, an oral daily maintenance dose without loading dose - steady-state blood concentration in approximately 7 days.Hence daily maintenance dose decided based on half-life ofthe drug.Usual digoxin therapeutic serum concentrations range - 0.8 to 2 ng/mL.(Note: Loading dose governed by volume of distribution).