Doxepin Pharmacology

Doxepin is under the class of tricyclic antidepressants. It can inhibit the reuptake of serotonin and norepinephrine.

In addition to the serotonin and norepinephrine reuptake inhibition mechanism, doxepin also has antihistamine type effects.

Because of the anticholinergic activity of doxepin, it is recommended to avoid this medication in the elderly, particularly at high doses.

Be aware that anticholinergics like doxepin can reduce the benefit of dementia medications.

CYP2D6 is an important enzyme in the metabolism of doxepin and drugs like bupropion that inhibit CYP2D6 can increase the concentrations of doxepin.

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Trazodone Pharmacology

Trazodone pharmacology is complex. It can inhibit serotonin reuptake, block histamine receptors, and possibly have alpha-blocking activity.

Side effects of trazodone include sedation, dizziness, and dry mouth. Rarely, priapism may occur. I’ve seen this nugget come up on pharmacology exams!

While trazodone is classified as antidepressant, it is often used to help manage insomnia.

Trazodone can possibly prolong the QT interval. Risk of other medications and patient specific parameters should be considered.

Trazodone concentrations can be increased with the use of CYP3A4 inhibitors and reduced with 3A4 inducers.

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