Doxepin: Nursing Drug Guide, Dose Confusion & NCLEX Review
Healthcare medication guide: verify whether the order is low-dose insomnia (3 to 6 mg) or antidepressant therapy (75 to 300 mg) before every dose—mixing strengths is a high-risk medication error with sedation, anticholinergic toxicity, and fatal TCA overdose.
Dose confusion is the bedside emergency: FDA-approved insomnia tablets are 3 to 6 mg at bedtime, while depression capsules commonly start at 75 mg/day and may reach 300 mg/day—giving capsule strength to a patient on Silenor-scale dosing (or vice versa) can cause profound sedation, anticholinergic toxicity, or fatal overdose. Antidepressant labeling carries a boxed warning for increased suicidal thinking and behavior in people 24 years and younger. Monitor all patients at initiation and dose changes for worsening depression, suicidality, and agitation. TCA overdose can widen QRS and cause dysrhythmias—obtain an ECG when ingestion is suspected. Do not give with MAO inhibitors; wait at least 14 days after MAOI discontinuation (including linezolid) before starting doxepin capsules per labeling.
📋 Contents
⚡ Quick facts
💡 Key takeaway
Before every dose, confirm product strength matches the indication on the order—3 to 6 mg insomnia is not interchangeable with 75 mg or higher depression dosing. After starts or changes, assess mood, behavior, orthostatics, and anticholinergic burden; if overdose is possible, obtain an ECG immediately and contact local poison control or toxicology per facility protocol.
Most common brand names
Doxepin is marketed in two clinically different oral forms: low-milligram film-coated tablets for insomnia (3 mg and 6 mg; brand Silenor) and higher-strength capsules for depression/anxiety (10, 25, 50, 75, 100, and 150 mg; legacy brand Sinequan and generics). A concentrated oral solution also exists—verify concentration on the label before administration.
Always match the product strength to the indication on the order. A 6 mg bedtime tablet is not a “small capsule” of the same drug class at antidepressant potency.
Why we give it — Indications
FDA labeling differs by formulation. Doxepin tablets (3 mg and 6 mg) are indicated for insomnia characterized by difficulty with sleep maintenance. Doxepin hydrochloride capsules are indicated for major depressive disorder in adults and, in older labeling, psychoneurotic depression and anxiety. Topical doxepin cream is used for pruritus—not covered in this oral nursing guide.
| Use | Detail |
|---|---|
| Insomnia (low-dose tablets) | 6 mg once daily at bedtime for adults; 3 mg for elderly when indicated; take within 30 minutes of bedtime; do not exceed 6 mg/day; avoid within 3 hours of a meal per insomnia labeling |
| Major depression (capsules) | Start 25 mg three times daily or 75 mg once daily; target 75–150 mg/day; maximum 100 mg three times daily (300 mg/day) for severe illness per capsule labeling |
| Anxiety with depression | Anti-anxiety effect may appear before full antidepressant benefit (often 2–3 weeks) |
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How it works
Doxepin is a dibenzoxepin tricyclic compound. At antidepressant doses it inhibits norepinephrine and serotonin reuptake; at low insomnia doses the primary nursing concern is potent histamine H1 antagonism causing sedation without assuming full antidepressant effect. Labeling notes the active ingredient is an antidepressant at doses roughly 10- to 100-fold higher than insomnia tablet strengths—so milligram mix-ups carry disproportionate risk. Anticholinergic, antihistaminic, and alpha-blocking effects drive dry mouth, constipation, urinary retention, orthostatic hypotension, and cardiac conduction changes.
Dosing overview
Read the order for formulation and indication before every administration. Insomnia and depression regimens are not interchangeable even though the ingredient name is the same.
Maintenance: Insomnia: continue lowest effective bedtime dose, not to exceed 6 mg/day. Depression: usual optimum 75–150 mg/day; once-daily bedtime dosing may be used up to 150 mg/day. With cimetidine, insomnia labeling limits adults to 3 mg/day because of increased doxepin exposure.
Missed dose: Not specified in the reviewed prescribing information. Do not double doses; contact prescriber or pharmacist if multiple doses are missed, especially after dose increases.
Onset, peak, duration, and half-life
| Parameter | Value | Nursing relevance |
|---|---|---|
| Onset (sedation) | Sedative effect may precede antidepressant effect | Do not assume early sedation means full therapeutic response |
| Antidepressant effect | Optimal effect may take 2–3 weeks (capsule labeling) | Continue suicidality monitoring during titration; sedation may appear earlier |
| Insomnia onset | Sedation from low-dose H1 blockade | Do not increase to capsule strengths if sleep remains poor without prescriber order |
| Half-life | Doxepin about 8–24 h (mean 17 h); nordoxepin about 33–80 h (mean 51 h) | Active metabolite prolongs sedation and interaction risk—especially with CYP inhibitors |
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Before you give it — Safety check
Pretreatment checks
- Screen for bipolar disorder history before treating depressive symptoms with antidepressant alone
- Review cardiovascular history (heart failure, recent MI, arrhythmia), seizure history (epilepsy), narrow-angle glaucoma, urinary retention, and fall risk
- Confirm no MAOI within 14 days; reconcile SSRIs and other serotonergic agents via medication reconciliation
- Assess baseline mood, sleep, and safety plan; involve family/caregivers per Medication Guide counseling
Contraindications
- Hypersensitivity to doxepin, inactive ingredients, or other dibenzoxepines
- Glaucoma or untreated anatomically narrow angles (pupillary dilation risk)
- Current or past urinary retention
- MAO inhibitors—including linezolid or intravenous methylene blue—unless 14-day washout completed per labeling
Important interactions
| Drug / class | Effect | Nursing action |
|---|---|---|
| MAO inhibitors (including linezolid) | Hyperpyretic crises, severe convulsions, deaths reported with TCA + MAOI | Hold doxepin; verify 14-day MAOI washout; pharmacist review before restart |
| SSRIs (fluoxetine, sertraline, paroxetine) | Inhibit CYP2D6—can raise TCA levels abruptly; fluoxetine needs long washout before starting TCA | Coordinate switches with pharmacy; monitor for toxicity (sedation, confusion, cardiac changes) |
| Other TCAs / sedatives | Additive anticholinergic and CNS depression | Compare with nortriptyline orders; avoid duplicate sedating psychotropics without prescriber intent |
| Anticholinergics | Paralytic ileus, hyperpyrexia, worsening urinary retention and confusion | Monitor bowel, temperature, mental status; hold and clarify if ileus symptoms develop |
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Administration
Route: Oral tablet (insomnia) or capsule (depression). Bedtime administration is standard for both indications because of sedation.
- Insomnia tablets: Give within 30 minutes of bedtime; instruct patient not to take with or soon after a meal (within 3 hours) because food delays absorption
- Capsules: May be given once daily at bedtime up to 150 mg/day or in divided doses per prescriber
- Perform orthostatic blood pressure checks when starting or increasing sedating doses in fall-risk patients
- Counsel that driving and hazardous machinery may be impaired the morning after dosing until individual response is known
Observe closely for clinical worsening, suicidality, and unusual behavior when therapy starts and whenever dose changes—especially in young adults. Report emergent anxiety, insomnia, irritability, hostility, akathisia, hypomania, or mania to the prescriber immediately.
Expected therapeutic response
- Gradual improvement in depressive symptoms over weeks—not immediate like anxiolytics
- Improved sleep when low-dose bedtime use is intended—distinguish sedation from mood recovery
- Stable vitals and ECG without new palpitations, syncope, or conduction abnormalities
Red flags — Stop and act
Escalate urgently for suicidality, cardiac toxicity, or severe anticholinergic compromise.
- New or worsening suicidal ideation, self-harm behavior, or violent impulsivity—immediate prescriber and safety intervention
- Sustained tachycardia, syncope, wide QRS, or ventricular arrhythmia on ECG—suspect TCA toxicity especially with overdose
- Seizures, coma, severe hypotension, or marked mental status change after ingestion or rapid dose escalation
- Paralytic ileus, urinary retention, or hyperpyrexia when combined with anticholinergic drugs
- Acute eye pain or vision changes in patients at risk for angle-closure glaucoma after pupillary dilation from antidepressants
Adverse effects
| Adverse effect | Frequency / severity | Nursing response |
|---|---|---|
| Dry mouth, constipation, urinary retention | Common anticholinergic effects; worse in elderly | Fall precautions, bowel protocol, monitor urine output; notify if retention or ileus |
| Blurred vision, mydriasis | Anticholinergic ophthalmic effects | Assess glaucoma risk; escalate acute eye pain or vision loss |
| Sedation, dizziness, orthostatic hypotension | Common CNS/cardiovascular effects | Rise slowly; night lights; syncope workup if recurrent |
| Arrhythmias, conduction delay, tachycardia | Serious cardiovascular effects at high doses or overdose | ECG when symptomatic or suspected ingestion; continuous monitoring per toxicology |
| Seizures, coma (overdose) | Critical toxicity | Activate emergency response; poison control per protocol |
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Overdose, toxicity, and antidote
Deaths may occur from TCA overdose. Toxicity develops rapidly; hospital monitoring is required as soon as possible. Multiple drug ingestion including alcohol is common in deliberate overdose.
Critical manifestations
- Cardiac dysrhythmias, severe hypotension, convulsions, CNS depression including coma
- ECG: QRS widening (≥0.10 s may indicate severity), rightward terminal QRS axis, prolonged QT, sinus tachycardia
- Agitation, hyperactive reflexes, hyperpyrexia, dilated pupils, or anticholinergic signs
Management (nursing priorities)
Obtain ECG and initiate cardiac monitoring immediately. Secure airway, IV access, activated charcoal after airway protection—emesis is contraindicated. Minimum six hours observation with monitoring; extend if toxicity signs appear. Sodium bicarbonate therapy may be used per toxicology for QRS prolongation. Contact local poison control or medical toxicology for current treatment guidance. No single antidote replaces structured toxicology care.
Contact local poison control or medical toxicology services per facility protocol when overdose is suspected. Psychiatric follow-up is often appropriate because overdose may be deliberate.
Look-alike / sound-alike and error prevention
- 6 mg Silenor tablet vs 75 mg capsule—same drug name, radically different potency; use independent double-check for strength and indication
- Doxepin vs amitriptyline—both sedating TCAs; verify correct agent on MAR and allergy record
- Tablet vs capsule appearance—do not substitute formulation without prescriber and pharmacy approval
- Concentrated oral solution—10 mg/mL; decimal errors and mL-to-mg confusion have caused overdoses with TCA solutions
- Duplicate sedatives—avoid overlapping TCAs, trazodone, or mirtazapine without clear intent
Practical bedside notes
| Topic | Bedside guidance |
|---|---|
| Meal timing (insomnia) | High-fat meal within 3 hours delays absorption and can blunt effect—counsel on empty-stomach bedtime dosing |
| Morning sedation | Next-day somnolence and impaired psychomotor performance reported—assess excessive sleepiness and fall risk |
| Quantity limits | Insomnia labeling: prescribe the least amount feasible to reduce intentional overdose risk |
| Abrupt stop | Not specified in the reviewed prescribing information for insomnia tablets; taper depression regimens per prescriber |
| Ask pharmacy when | Wrong strength dispensed, cimetidine added, SSRI switch, or MAR shows “doxepin” without mg strength |
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High-risk populations
| Population | Considerations |
|---|---|
| Children & adolescents | MDD capsules not for use in children; insomnia tablets not established under 18 years per labeling—suicidality risk if antidepressant doses used |
| Young adults (18–24) | Higher suicidality risk versus placebo in short-term studies—intensify monitoring at initiation and dose changes |
| Older adults | Insomnia tablets: start 3 mg HS; depression capsules: lower initial doses than younger adults; confusion, oversedation, and falls predominate |
| Cardiovascular disease | Arrhythmias and conduction delays reported—avoid acute post-MI period; watch vitals and ECG |
| Pregnancy / lactation | Third-trimester TCA exposure may cause poor neonatal adaptation—monitor neonates; breastfeeding not recommended (infant sedation and respiratory depression reported) |
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Monitoring and documentation
Monitor
- Mood, behavior, suicidality, sleep, and functional status at each contact during the first months and after dose changes
- Heart rate, blood pressure, orthostatic symptoms, and ECG when cardiac history or overdose concern exists
- Anticholinergic burden: mental status, bowel function, urine output, temperature, vision changes
Document
- Baseline and follow-up safety assessments, family/caregiver education on warning symptoms
- Dose, time, and patient response; any PRN sedative overlap
- ECG and poison-control consultation when toxicity is suspected
Patient teaching
- Verify you have the correct strength: insomnia tablets are 3 or 6 mg; depression capsules are much higher—never interchange them
- Take insomnia tablets within 30 minutes of bedtime on an empty stomach (not within 3 hours of a meal) per labeling
- Antidepressants may increase suicidal thoughts in some people—seek help immediately for worsening depression, agitation, panic, insomnia, irritability, hostility, or thoughts of self-harm
- Do not stop suddenly without talking to the prescriber; withdrawal symptoms can occur with longer-term depression dosing
- Rise slowly from sitting or lying down; avoid alcohol and other sedatives unless approved
- Report dry mouth, constipation, urinary difficulty, palpitations, dizziness, eye pain, or vision changes
- Keep appointments; full antidepressant benefit may take weeks
The Hold Rule
Do not give and contact the prescriber/pharmacist when:
- MAOI used within 14 days (including linezolid) or serotonergic switch without pharmacy-approved washout
- Active suicidal plan, overdose ingestion, or emergent mania/psychosis
- Symptomatic wide QRS, unstable arrhythmia, or seizure after recent dose
- Paralytic ileus, urinary retention requiring intervention, or acute angle-closure glaucoma symptoms
- Dispensed product strength does not match order (e.g., 75 mg capsule for a 6 mg insomnia tablet order)
- Patient took insomnia tablet within 3 hours of a full meal and reports no benefit—clarify timing before escalating dose
Hold parameters may vary by institutional protocol. Follow prescriber orders, pharmacy guidance, and facility policy.
Clinical practice integration and workflow
Doxepin errors often begin with the right drug name and the wrong milligrams. Pair indication verification with suicidality and cardiac monitoring whenever antidepressant-strength therapy is possible.
1. Check-before-you-give protocol
- Right patient, drug, strength, route, time—and right indication (insomnia 3–6 mg vs depression 75–300 mg)
- MAOI/linezolid history and recent SSRI therapy documented
- Suicidality screen current when initiating or changing dose
- Fall and orthostatic precautions in place for sedating doses
2. High-alert and safety badge
High-risk TCA — dose confusion between insomnia and depression strengthsTreat suspected overdose as a monitored cardiac emergency. Limit quantities on discharge per labeling. Use fall risk assessment when starting sedating doses in older adults.
3. Clinical workflow: hold and question rules
- If MAR says “doxepin 6 mg HS” but the blister pack is a 75 mg capsule, hold and call pharmacy before administration
- If fluoxetine was stopped recently and doxepin capsules are ordered without washout documentation, hold and call pharmacy
- Any suspected ingestion with QRS ≥0.10 s, hypotension, or altered mental status triggers ECG monitoring and toxicology consult per protocol
4. Critical teach-back questions
- “What mood or behavior changes should you report right away?” (Worsening depression, suicidal thoughts, agitation, insomnia, irritability, unusual behavior.)
- “How will you take this at home—tablet or capsule, and how many milligrams?” (Teach patients to verify 3 or 6 mg insomnia tablets versus higher capsule strengths; seek emergency care for extra tablets.)
5. Care coordination
Pharmacist: MAOI washout, SSRI-to-TCA switches, drug level concerns in elderly, and overdose management pathways
Psychiatry / prescriber: Suicidality escalation, bipolar screening failures, and need to discontinue or change antidepressant class
🧠 Quick mental checklist
- Does the order say insomnia (3–6 mg tablet) or depression (capsule)—and does the package match?
- Was the bedtime dose taken on an empty stomach (insomnia tablets) and at the right time?
- Any suicidal ideation, agitation, or behavioral change since the last dose?
- Orthostatics, sedation score, and ECG if wrong strength given or ingestion suspected?
- Anticholinergic load: confusion, constipation, urinary retention—especially in older adults?
Doxepin NCLEX practice questions
Practice NCLEX-style clinical judgment practice for doxepin using a tabbed case (MAR, labs, vitals, nursing notes), then priority action, cue recognition (SATA), ECG trend interpretation, MAOI washout cloze, ordered documentation steps, and a matrix sorting suicidality versus cardiac versus anticholinergic findings—recognise cues → analyse → prioritise → act → evaluate outcomes.
Select a tab to view MAR, labs, vitals, and nursing note details for this case.
- Doxepin 6 mg tablet PO at bedtime — indication: insomnia (sleep maintenance)
- Overnight MAR entry: one 75 mg capsule given in error (pharmacy bar-code mismatch)
- Cimetidine 300 mg PO BID — started 2 days ago
- Docusate 100 mg PO BID PRN constipation
- Admission ECG: sinus rhythm, QRS 0.08 s, QTc 418 ms
- Today 0900 (after 75 mg capsule error): QRS 0.10 s, sinus tachycardia 104/min
- BMP: sodium 139, potassium 3.9, creatinine 1.0 mg/dL
- No serum doxepin level on routine panel
- 0700: BP 112/68, HR 82, RR 14, SpO2 98% on room air
- 0900: BP 96/58, HR 104, RR 18, SpO2 97%, temp 37.0 °C
- Orthostatics: lying BP 110/66 → standing BP 90/52 with lightheadedness
- 79-year-old admitted for chronic insomnia; history of falls; uses reading glasses
- 2200 prior shift: Nurse administered green capsule believing it was “doxepin 6” — pharmacy later confirmed 75 mg capsule
- 0900: Difficult to arouse, dry mouth, hasn’t voided in 8 h, denies chest pain
- Patient states, “I only take a tiny sleep pill at home—I don’t know why that capsule was so big.”
Answer key & rationale
Frequently asked questions
Can I give a 75 mg doxepin capsule for a 6 mg insomnia order?
No. Insomnia tablets are 3 to 6 mg at bedtime (maximum 6 mg/day). Depression capsules often start at 75 mg/day and may reach 300 mg/day. A 75 mg capsule is about twelve times an adult insomnia dose and can cause dangerous sedation, anticholinergic toxicity, and cardiac conduction changes. Hold the dose, verify with pharmacy, and report the error per facility policy.
How long must a nurse wait after stopping an MAOI before starting doxepin?
Doxepin is contraindicated with monoamine oxidase inhibitors. When replacing an MAOI with doxepin, allow a minimum of 14 days after the MAOI is discontinued before initiating doxepin, then titrate cautiously per prescribing information.
What ECG changes suggest TCA overdose toxicity?
Labeling states QRS axis or width changes are clinically significant indicators of tricyclic antidepressant toxicity. A rightward terminal QRS shift with prolonged QT and sinus tachycardia are specific and sensitive for first-generation TCA overdose. Obtain an ECG immediately when overdose is suspected.
Is doxepin safe during breastfeeding?
Labeling recommends against breastfeeding because doxepin and nordoxepin are present in human milk, with reports of infant sedation, respiratory depression, poor feeding, and hypotonia. LactMed scores doxepin as not recommended during breastfeeding, especially with newborns or preterm infants. Discuss safer alternatives with the prescriber.
Why are older adults at higher risk with doxepin?
Insomnia labeling recommends 3 mg at bedtime in elderly patients (maximum 6 mg/day). Geriatric patients are more sensitive to confusion, oversedation, orthostatic hypotension, urinary retention, and falls. Depression capsules should start at lower doses than younger adults with close observation.
References
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U.S. National Library of Medicine. Doxepin hydrochloride capsule — Full prescribing information (major depressive disorder). DailyMed.https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f3c242dd-426e-4c69-8f21-2645361d5f27
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U.S. National Library of Medicine. Doxepin tablet — Full prescribing information (insomnia). DailyMed.https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=1bec1223-5239-4eb6-a9e8-62444106d2c0
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U.S. Food and Drug Administration. Suicidality in children and adolescents being treated with antidepressant medications.https://www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-suicidality-children-and-adolescents-being-treated-antidepressant
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Drugs and Lactation Database (LactMed). Doxepin. Bethesda (MD): National Institute of Child Health and Human Development.https://www.ncbi.nlm.nih.gov/books/NBK501181/
Review and transparency
This medication guide is written and reviewed using NurseOnShift editorial and clinical review standards.
Educational use only. This content does not replace clinical judgment, prescriber orders, pharmacist guidance, product labeling, or institutional protocols.