How is monitoring of blood medication levels useful in the management of schizophrenia?

Updated: Mar 16, 2018
  • Author: Frances R Frankenburg, MD; Chief Editor: Glen L Xiong, MD  more...
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Regular measurement of blood medication levels in the blood would be helpful in schizophrenia, for the following reasons:

  • Patients may not always take their medications, and checking drug levels can detect this noncompliance

  • Patients may not always be the best reporters of side effects, and monitoring medication levels can occasionally help the clinician detect toxicity

  • Smoking tobacco products induces the liver enzyme CYP1A2 (though nicotine patches, nicotine inhalers, and chewing tobacco do not); this enzyme metabolizes a number of antipsychotic drugs, so that, for example, patients who stop smoking while being treated with clozapine or olanzapine often experience increased antipsychotic levels; a patient who has stopped smoking may have a variety of complaints, and checking drug levels can help determine their etiology

For most antipsychotic medications, however, clear dose-response curves have not been established, and in clinical practice, drug levels are rarely monitored.

There are 2 exceptions to this general statement. Plasma concentrations of haloperidol are correlated to some degree with clinical effects, and levels in the range of 15-25 ng/mL are thought to be optimal. Plasma concentrations of clozapine in the range of 300-400 ng/mL may be optimal.

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