<prompt> At 12 h after IV administration of a bolus dose, the plasma level of a drug is 3 mgL. If the Vd10 L and the elimination half-life 6 h, what was the dose administered?120 mg180 mg240 mg480 mg  <response>: At 12 h after IV injection which corresponds to two half-lives of the drug, the plasma level is 3mgL. Extrapolating back to zero time, by doubling plasma level for each half-life, results in an initial plasma level at zero time C03x2x2mgL12mgL.DoseinjectedVd xC010Lx12mgL120mg 