Reading the concentration-time curve
A pharmacokinetic curve plots the concentration of a drug in blood plasma against time after a dose. After oral administration the curve rises during absorption, reaches a peak, then falls as the drug is distributed into tissues and eliminated. The peak concentration is called Cmax and the time at which it occurs is Tmax. The total exposure is captured by the area under the curve (AUC).
The shape reflects competing processes: absorption pulling concentration up early, and distribution plus elimination pulling it down. For an intravenous dose there is no absorption phase, so the curve starts high and declines immediately.
Half-life and steady state
Elimination is often described by a half-life, the time for plasma concentration to fall by half once absorption and distribution are largely complete. Half-life governs how often a drug must be dosed and how long it takes to reach steady state with repeated dosing, generally about four to five half-lives.
These are general pharmacology concepts, not dosing instructions. Actual drug regimens depend on the specific agent, the patient, and clinical judgement, and should be set by a qualified prescriber.