This information describes what happens to a drug following administration and includes absorption, distribution, metabolism, and excretion of the drug. This lesson leads smoothly into the pharmacokinetics unit. The teacher must know the components of the therapeutic drug range graph that the students will create. The relationship of the drug response and time is the time-response relationship. Duration of action is the length of time that a drug produces an effect.
Most drugs produce effects over a constant period of time.
The time from drug administration to the first observable effect is called the onset of action. The drug response will continue as long as there is enough concentration at the site of action. As the drug is metabolized and excreted, the response decreases because the level of drug is decreasing. Termination of action occurs when the response is no longer observed. Duration of action refers to the period from the onset of action to the time when the response is no longer perceptible.