Definition of Therapeutic Level

therapeutic levelTherapeutic Level – the amount of a drug in the blood circulation that is necessary to achieve and sustain the desired effect for treatment, which is usually a steady state with little variation between the drug’s peak level and trough level.

Doctors calculate dosages to achieve a therapeutic level, factoring the person’s age, body weight, and other medications with which interactions are possible.

For most drugs, blood drawn at any time provides the needed information about the drug’s concentration in the blood. At the onset of medication therapy or when taking a drug that has a narrow therapeutic index (nti), blood tests taken to measure both peak and trough levels may provide more useful information to assess whether the drug is at therapeutic level.

It often is valuable to tell the doctor or the lab the time of the last dose of the medication, which may help to determine whether doses are spaced appropriately.


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