This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Digoxin is obtained from a plant product and has a half-life of 36 hours. How does this information help us in formulating treatment? 
Select and explain. 
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: To adjust maintenance dose of digoxin required to keep the blood levels within therapeutic range
Answer: A: To adjust maintenance dose of digoxin required to keep the blood levels within therapeutic range 
Explanation: 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).