What the FDA labels say about taking them together
Cimetidine and doxepin
Doxepin's FDA label (Silenor) of April 21, 2026 names cimetidine in its drug interactions section; cimetidine's label does not name doxepin itself but warns about its class (Tricyclic antidepressants). The doxepin label: “Cimetidine SILENOR exposure is doubled with concomitant administration of cimetidine, a nonspecific inhibitor of CYP isozymes.”
Check it at the source: the cimetidine FDA label on DailyMed (effective July 15, 2026, Mylan Pharmaceuticals Inc.); the doxepin FDA label on DailyMed (effective December 30, 2025, Leading Pharma, LLC).
What does the cimetidine label say about doxepin?
Cimetidine's label does not name doxepin itself; it warns about its class (Tricyclic antidepressants):
Cimetidine label, drug interactionsDrug Interactions Cimetidine tablets, apparently through an effect on certain microsomal enzyme systems, has been reported to reduce the hepatic metabolism of warfarin-type anticoagulants, phenytoin, propranolol, nifedipine, chlordiazepoxide, diazepam, certain tricyclic antidepressants, lidocaine, theophylline, and metronidazole, thereby delaying elimination and increasing blood levels of these drugs.
Source: FDA drug label (Cimetidine), Mylan Pharmaceuticals Inc., effective July 15, 2026 (SPL set 06c0a509-026f-44e0-9975-a94a8de51d43), via openFDA; the full label on DailyMed
What does the doxepin label say about cimetidine?
Silenor label (Currax Pharmaceuticals LLC, April 21, 2026), drug interactionsCimetidine SILENOR exposure is doubled with concomitant administration of cimetidine, a nonspecific inhibitor of CYP isozymes.
Prudoxin label (Mylan Pharmaceuticals Inc., June 29, 2017), drug interactionsThe drugs that inhibit cytochrome P450 2D6 include some that are not metabolized by the enzyme (quinidine; cimetidine) and many that are substrates for P450 2D6 (many other antidepressants, phenothiazines, and the Type 1C antiarrhythmics propafenone and flecainide).
Source: FDA drug label (Silenor, NDA022036), Currax Pharmaceuticals LLC, effective April 21, 2026 (SPL set 1bec1223-5239-4eb6-a9e8-62444106d2c0), via openFDA
Source: FDA drug label (Prudoxin, NDA020126), Mylan Pharmaceuticals Inc., effective June 29, 2017 (SPL set ca53346b-8ab3-4722-98f6-cf272706d3fa), via openFDA
Source: FDA drug label (DOXEPIN HYDROCHLORIDE), Leading Pharma, LLC, effective December 30, 2025 (SPL set e6a4cb10-1928-4abe-8797-404c9ddc37dd), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Cimetidine | Doxepin | |
|---|---|---|
| Labeled for | Acid reflux and ulcers | Depression, Anxiety, Eczema (atopic dermatitis), Insomnia |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.236 per tablet 300 mg tablet | $0.0779 per capsule 10 mg capsule |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once