Additional Resources


The transition of drug from the site of administration to the blood circulation.

A group of injectable antibiotics active against a wide range of bacteria.

A measure of how much of the drug makes it into the bloodstream and becomes available to the target tissue.

Sampling technique for Cyclosporine. The sample is drawn 2h after taking the last drug dosage, which can improve monitoring vs. trough levels.

The maximum concentration of drug in the blood.

The minimum concentration of drug in the blood.

The transition of drug from the blood circulation to the target tissue(s).

Dosage Regimen
The complete description of drug administration, includes dose rate and interval.

Removal or transformation of a drug in circulation, usually via the kidney and liver. Many factors affect a drug’s elimination rate, including hepatic and renal function, age, disease, protein binding, etc.

Elimination Half-life
Time required for the amount of drug in the body to decrease by 50%.

Elimination of a drug via renal, biliary, or pulmonary processes.

First Pass Loss
Removal of a fraction of drug dose by the liver before it reaches the systemic circulation.

A measurement of how long a drug stays in the blood.

Loading Dose
Dose(s) of drugs given at the onset of therapy to rapidly provide a therapeutic effect. Use of a loading dose prior to a maintenance dosage regimen will shorten the time required to approach a steady state.

Maintenance Dose
A dosing regimen designed for chronic therapy.

The conversion of a drug from the circulating blood to the target tissue(s).

Peak Serum Concentration
The highest serum drug concentration that occurs following a single dose or at steady state within a dosing interval. Determining the exact peak requires numerous serial blood samples.

The study of how drug levels change over time in the body.

Protein Binding
Serum proteins function as carriers for many drugs, hormones, etc and transport the substances around the body in the bloodstream. Only the unbound or free fraction is available to act on the target tissues.

Steady State
Represents the equilibrium between the amount of drug given and the amount eliminated over the dosing interval. In general it takes a drug four to five half-lives to reach a steady state. Sampling should occur when the drug has reached its steady state to judge efficacy and toxicity of the drug therapy. Steady state should not be confused with the therapeutic range.

Steady State Concentration
Serum drug or metabolite concentrations during a dosing interval after a steady state has been achieved. Steady state concentrations fluctuate between a maximum (peak) and minimum (trough) concentration with each dosing interval.

Therapeutic Range
Range of drug concentrations associated with high degree of efficacy and low risk of dose-related toxicity in majority of patients.

Trough Serum Concentration
The lowest drug concentration during a dosing interval when drug is given intermittently. The trough concentration generally occurs immediately before administration of the next dose.

Total Drug Concentration
The sum of unbound and bound drug in serum or plasma.

Unbound Drug Concentration
The concentration of drug in serum and plasma that is free and not bound to proteins. The unbound drug concentration in serum is more closely associated with drug response than closely associated with drug response than total drug concentrations.