Clozapine and Doxepin interaction
Clozapine and Doxepin: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Clozapine (Clozaril) label · effective 2025-06-06
When possible, avoid concomitant use, with other anticholinergic medications because the risk for anticholinergic toxicity or severe gastrointestinal adverse reactions is increased [see Warnings and Precautions ( 5.7 ), Drug Interactions ( 7.1 )].
• Anticholinergic Toxicity : When possible, avoid use with other anticholinergic drugs and use with caution in patients with a current diagnosis or prior history of constipation, urinary retention, clinically significant prostatic hypertrophy, or other conditions in which anticholinergic effects can lead to significant adverse reactions.
Use with caution in patients with a current diagnosis or prior history of constipation, urinary retention, clinically significant prostatic hypertrophy, or other conditions in which anticholinergic effects can lead to significant adverse reactions.
Such drugs include specific antidepressants, phenothiazines, carbamazepine, and Type 1C antiarrhythmics (e.g., propafenone, flecainide, and encainide).
From the Doxepin (Silenor) label · effective 2026-04-21
Potential additive effects when used in combination with CNS depressants or sedating antihistamines.
Although behaviors such as "sleep-driving" may occur with hypnotics alone at therapeutic doses, the use of alcohol and other CNS depressants with hypnotics appears to increase the risk of such behaviors, as does the use of hypnotics at doses exceeding the maximum recommended dose.
When taken with SILENOR, the sedative effects of alcoholic beverages, sedating antihistamines, and other CNS depressants may be potentiated [s ee Warnings and Precautions (5.2) and Drug Interactions (7.3 , 7.4) ].
Patients should be cautioned about potential additive effects of SILENOR used in combination with CNS depressants or sedating antihistamines [s ee Warnings and Precautions (5.2) and Drug Interactions (7.4) ].
CNS Depressants and Sedating Antihistamines: Sedative effects may be increased with doxepin.
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.