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Doxepin plasma concentrations: is there really a therapeutic range?
1Department of Psychiatry and Psychotherapy, Klinikum rechts der Isar der Technischen Universität München, Gernany. Stefan.Leucht@Lrz.tu-muenchen.de
Journal of Clinical Psychopharmacology
|July 31, 2001
Summary
Tricyclic antidepressant doxepin levels are often subtherapeutic, with most patients falling below the widely cited 150-250 ng/mL range. Further research is needed to establish an accurate therapeutic range for effective depression treatment.
Area of Science:
- Pharmacology
- Psychiatry
- Clinical Chemistry
Background:
- Tricyclic antidepressants, including doxepin, remain crucial for depression treatment.
- Therapeutic drug monitoring of doxepin is standard practice in psychiatric clinics.
- Existing literature suggests a therapeutic range of 150-250 ng/mL for doxepin and its metabolite.
Purpose of the Study:
- To investigate the actual serum concentrations of doxepin in patients undergoing treatment.
- To evaluate the validity of the commonly cited therapeutic range for doxepin.
- To propose a revised working range based on empirical data and literature review.
Main Methods:
- Analysis of a serum-level databank (N=217) using high-performance liquid chromatography.
- A questionnaire survey of psychiatric university departments and laboratories in the U.S. and Germany.
- Comprehensive review of published literature on doxepin serum concentrations and therapeutic effects.
Main Results:
- Only 9% of analyzed samples fell within the 150-250 ng/mL range; 88% were subtherapeutic.
- The mean steady-state serum concentration of doxepin + desmethyldoxepin was 89+/-75 ng/mL with a mean daily dose of 143+/-30 mg.
- No correlation was found between serum concentrations and clinical improvement.
Conclusions:
- Current evidence is insufficient to support the widely adopted therapeutic range for doxepin.
- Suggested therapeutic ranges are often too high compared to concentrations found in original studies.
- A preliminary working range of 50-250 ng/mL is proposed pending a methodologically sound study to determine an evidence-based therapeutic range.
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