<prompt> A 40-year-old man was brought to the ER after ingesting an unknown quantity of phenobarbital, the plasma level of which was 50 mgL on admission. Pharmacokinetic parameters for phenobarbital are: Vd40 L, CL6 Lday, half-life 4 days, oral bioavailability f1. The quantity of the drug that the patient ingested must have been close to100 mg500 mg1 g2 g  <response>: Although there is no information regarding the time lapse between phenobarbital ingestion and ER admission, we might guess that the blood level approximates C0 and is certainly no higher. With such an assumption, the dose ingested is given by:DoseC0xVd f50mgLx40L12000mg2g 