Silenor Drug Interactions: What to Avoid and What to Tell Your Doctor

Before starting Silenor (doxepin), it's essential to tell your doctor and pharmacist about all the medications, supplements, and substances you take. Silenor has several clinically significant interactions — some of which can be dangerous. This guide walks you through the most important ones in plain language.

Absolute Contraindication: MAOIs (Monoamine Oxidase Inhibitors)

The most serious interaction is with MAOIs. Combining Silenor with MAOIs can cause a potentially fatal reaction, including severe cardiovascular instability, hyperthermia, seizures, and death. Never take Silenor if you are currently taking an MAOI or have taken one within the past 2 weeks.

MAOIs include: phenelzine (Nardil), tranylcypromine (Parnate), isocarboxazid (Marplan), selegiline (Emsam, Eldepryl), linezolid (Zyvox — an antibiotic with MAOI properties), and methylene blue.

Major Interaction: Cimetidine (Tagamet)

Cimetidine (brand name Tagamet), a stomach acid reducer available over the counter, significantly increases doxepin blood levels by inhibiting liver enzymes that metabolize it. If you take cimetidine while on Silenor, you may experience excessive sedation or other enhanced side effects. Tell your doctor if you use cimetidine or any H2 blocker.

Alternative acid reducers like ranitidine, famotidine, or proton pump inhibitors (omeprazole, pantoprazole) have a less significant interaction with doxepin. Ask your doctor or pharmacist about switching if you regularly need antacid treatment.

Important Interaction: Alcohol and CNS Depressants

Combining Silenor with alcohol or other central nervous system (CNS) depressants can cause additive sedation and significantly increase the risk of complex sleep behaviors (sleep-driving, sleep-eating, sleep-walking). Avoid alcohol on nights when you take Silenor.

Other CNS depressants to be cautious about include:

Opioid pain medications (hydrocodone, oxycodone, morphine, fentanyl)

Benzodiazepines (diazepam, lorazepam, alprazolam, clonazepam)

Muscle relaxants (cyclobenzaprine, carisoprodol, baclofen)

First-generation antihistamines (diphenhydramine/Benadryl, hydroxyzine)

Sodium oxybate (Xyrem/Lumryz) — combination with CNS depressants is contraindicated

Important Interaction: Serotonergic Drugs

At higher doses, doxepin has serotonergic activity. At insomnia doses (3–6 mg), this risk is minimal but still worth flagging with your doctor if you're also taking:

SSRIs (fluoxetine, sertraline, escitalopram, paroxetine, citalopram)

SNRIs (venlafaxine, duloxetine, desvenlafaxine)

Triptans (sumatriptan, rizatriptan — used for migraines)

Tramadol or other opioids with serotonergic properties

CYP Enzyme Interactions: Drugs That Affect Doxepin Levels

Doxepin is primarily metabolized by liver enzymes CYP2C19 and CYP2D6. Drugs that inhibit these enzymes can increase doxepin blood levels; drugs that induce these enzymes can decrease doxepin levels.

CYP2D6 inhibitors (increase doxepin levels): fluoxetine (Prozac), paroxetine (Paxil), bupropion (Wellbutrin), quinidine, terbinafine

CYP2C19 inhibitors (increase doxepin levels): omeprazole, esomeprazole, fluvoxamine, clopidogrel

CYP inducers (decrease doxepin levels): rifampin, carbamazepine, phenytoin, St. John's Wort

QT-Prolonging Drugs

At the 3–6 mg insomnia doses, clinical studies have shown Silenor does NOT significantly prolong the QT interval — unlike higher doses of tricyclic antidepressants. However, it's still worth informing your doctor if you take any QT-prolonging medications (certain antibiotics, antiarrhythmics, or antipsychotics) as a general precaution.

Medications to Tell Your Doctor About Before Starting Silenor

Share your complete medication list with your prescriber. Specifically mention:

All antidepressants, anti-anxiety medications, and mood stabilizers

Any OTC sleep aids or antihistamines you take (Benadryl, Unisom, ZzzQuil)

Any supplements known to affect sleep or mood (melatonin, valerian, 5-HTP, St. John's Wort)

Cimetidine (Tagamet) or any other acid reducers you take regularly

Opioid pain medications and other controlled substances

For more on what side effects to watch for, see: Silenor Side Effects: What to Expect and When to Call Your Doctor.

Once you've confirmed your medication plan with your doctor, medfinder can help you find a pharmacy near you with Silenor or generic doxepin in stock.