Answer: Cmax refers to the maximum concentration that a drug reaches in the body.
Cmax is a term that is often used in the study of pharmacokinetics, which is the field that focuses on understanding the actions that the body has on drugs. Cmax is a numerical value that describes the maximum concentration of the drug in the body. It is generally measured in g/L.
Cmax does not say anything about the distribution of the drug. Usually, Cmax refers to the concentration of the drug in the plasma. But, the drug may be at a dramatically different concentration in certain organs. The organs which accumulate drug including the circulation and they are sometimes called the “central compartment.” For example, the liver, which tends to accumulate drug for metabolic breakdown, generally has a higher Cmax than other organs. The blood-brain barrier is an adaptation that can prevent drugs in the bloodstream from reaching the brain, so drug concentration may be lower in the brain than in the plasma.
Cmax can be contrasted with Cmin, which is the lowest concentration of the drug in the body. If the drug delivery is timed correctly, the Cmin is right before the next dose of the drug.
Tmax is defined as the time at which Cmax is attained after drug administration. Therefore, the units of measure for Tmax is time.