The pharmacokinetic propeies of a new antihistamine are being studied in normal volunteers during phase I clinical trials. The clearance and half-life of the drug are determined to be 4.0 L/hour and 10 hours, respectively. Which of the following values is the approximate volume of distribution for this drug?: (A) 0.06 L, (B) 14 L, (C) 45 L, (D) 60 L
Answer is D. The volume of distribution of a drug can be determined using the following equation: t1/2 = (0.693 x Vd)/CL Therefore, 10 hours = (0.693 x Vd)/(4.0 L/hour), 40 hours = 0.693 x Vd, Vd = 58 L which is approximately 60 L.