The page below is a sample from the LabCE course Pharmacology in the Clinical Lab: Therapeutic Drug Monitoring and Pharmacogenomics. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Steady State Example

If the drug Gentamicin has an elimination half-life of 12 hours and is given every 12 hours, the drug should reach steady state after 5 half-lives (60 hours).

Notice in the diagram that this kind of dosing results in a 'sawtooth' pattern. Peaks correspond to the times right after the drug is taken; troughs correspond to the times right before the next dose.
Of course a physician may want to get a patient into the therapeutic range more quickly. In these cases a higher loading dose of drug can be prescribed initially with instructions that after the first couple of doses, the dose should be reduced.