Question

To be effective, a certain drug must not drop below 15 mg in the body. A 120
mgs of that drug was administered to a patient. How much time will it take for
that drug to reach the 15 mg minimum level. The drug's half-life is 30 minutes.

Answer 1

Thus, it follows that after 4 to 5 half-lives, the plasma concentrations of a given drug will be below a clinically relevant concentration and thus will be considered eliminated. Conversely, the accumulation of a drug can reach a steady-state during an infusion