Prescribing Duloxetine

At a glance

The SNRI for depression or anxiety that comes with a pain syndrome, or when you want SNRI reach without venlafaxine's BP rise.

How to doseFull section

Comes as

Delayed-release capsule20, 30, 40, 60 mg

Example photos; looks vary by maker. Click to enlarge.

In shortLabel: depression 40 to 60 mg a day, GAD 60 mg for most adults under 65. In practice: 30 mg for 1 week, then 60 mg, and stop at 60 mg. GAD above 60 mg only if a decision is made to go higher, in 30 mg steps; no added benefit above 60 mg.

FDA labelIn practice

A row across both columns means the label and usual practice agree. Off-label marks the few places where practice goes beyond what the label allows.

Adultsdepression, GAD, pain

DepressionFDA labelRecommended start 40 mg a day (20 mg twice daily) to 60 mg a day (once daily or 30 mg twice daily).In practice30 mg once daily for 1 week, then 60 mg once daily.

Anxiety (GAD)FDA label60 mg once daily for most adults under 65. For some, starting at 30 mg once daily for 1 week may be desirable.In practice30 mg once daily for 1 week, then 60 mg once daily.

Diabetic nerve painFDA label60 mg once daily. No evidence higher doses add significant benefit, and they are clearly less well tolerated.In practice60 mg a day; some go to 120 mg (past the label's 60 mg).

FibromyalgiaFDA label60 mg once daily. Begin with 30 mg once daily for 1 week to adjust first.In practiceStart 30 mg, titrate to 60 mg, then 120 mg if response is partial (past the label's 60 mg).

Chronic musculoskeletal painFDA label60 mg once daily. Begin with 30 mg once daily for 1 week to adjust first.In practice60 mg a day; some go to 120 mg (past the label's 60 mg).

MaximumFDA label120 mg was shown effective, but no evidence that doses above 60 mg a day add benefit.In practiceStop at 60 mg for depression and GAD (label allows 30 mg steps above 60 mg in GAD). Fibromyalgia: 120 mg if partial response. Pain: some go to 120 mg.

MaintenanceFDA labelPeriodically reassess the need for maintenance treatment and the appropriate dose.

Ages 7–17FDA labelGAD, 7–17: 30 mg once daily for 2 weeks before considering 60 mg. Fibromyalgia, 13–17: 30 mg once daily to start.In practiceStart 30 mg once daily, range 30–60 mg.

Older adultsFDA labelGAD: 30 mg once daily for 2 weeks before considering 60 mg. Thereafter patients may benefit above 60 mg.In practiceStart 30 mg or lower, and go slow.

Liver or kidney diseaseFDA labelAvoid in chronic liver disease or cirrhosis, and in severe renal impairment (GFR under 30 mL/min).In practiceNot recommended in any hepatic insufficiency, or in severe or end-stage renal impairment (CrCl under 30 mL/min).

When to take itFDA labelWith or without meals. Swallow whole; do not chew or crush.In practiceTake with food or a snack. Splitting twice daily is a legitimate tolerability tool for nausea or dizziness (label BID: depression only).

Stopping and switchingFDA labelReduce gradually when possible. Do not start with linezolid or IV methylene blue. MAOIs intended to treat psychiatric disorders: washout both ways.In practiceStep down about 25–50% every 2–4 weeks, slower near the end. The 20 and 30 mg capsules allow smaller steps.

IndicationsFull section

FDA-approved

Major depressive disorder

GAD (adults; children 7–17)

Fibromyalgia

Diabetic peripheral neuropathic pain

Chronic musculoskeletal pain (low back pain, OA)

Off-label, evidence-based

Stress urinary incontinence (approved in Europe)OCD (weak; sertraline is better)

Boxed warningsFull section

Suicidality in patients under 25Class warning; greatest in the first 1–2 wk and after dose changes; monitor closely early

ContraindicationsFull section

MAOIs14 d after an MAOI before duloxetine; 5 d after duloxetine before an MAOI

Hepatic insufficiency, liver diseaseAvoid: hepatotoxicity signal; clearance falls in cirrhosis

Heavy alcohol useAvoid: the hepatotoxicity setup

MonitorFull section

ALTBaseline and at least once after starting; recheck for RUQ pain, jaundice, dark urine, fatigue

Alcohol use, hepatotoxic co-medsBefore starting: heavy drinking plus duloxetine is the hepatotoxicity setup

Blood pressureBaseline and periodically, as the label directs

SuicidalityFirst 1–2 wk and after dose changes, under 25

Activation, maniaAs with any antidepressant; screen for bipolarity first

SodiumIf confusion, lethargy or falls, especially in the elderly (SIADH)

No routine ECG, CBC, electrolytes or drug levels. Stop for rising ALT; don't wait for jaundice.

Drug interactionsFull section

Drug-drug

MAOIsNever combine: serotonin syndrome, potentially fatal; 5-week washout from fluoxetine to an MAOI

Fluvoxamine, ciprofloxacin, quinolonesStrong CYP1A2 inhibitors markedly raise levels; avoid or dose-reduce

Linezolid, St. John's wort, dextromethorphanSerotonin syndrome risk, as with other antidepressants; its 2D6 block compounds this

Tricyclic antidepressants2D6 inhibition can raise TCAs substantially; cut the TCA dose, monitor levels

Aripiprazole, risperidone, brexpiprazoleRaised levels; akathisia and EPS risk

Smoking, cannabis (and quitting)Induce CYP1A2, lowering levels within ~3 days; quitting raises levels, watch side effects

NSAIDs, anticoagulants, antiplateletsAdditive GI-bleed risk via platelet serotonin depletion

Beta-blockers, amphetamines2D6 substrates; monitor

Stimulants, decongestantsTheoretical additive pressor effect; its own BP effect is minimal

CYP enzymes

CYP1A2Substrate (primary)Fluvoxamine, ciprofloxacin raise levels; smoking and cannabis lower them; quitting raises them

CYP2D6Substrate; moderate inhibitorLess potent than paroxetine or fluoxetine; raises TCAs, some antipsychotics; poor metabolizers run higher

Must counselFull section

NauseaCommon early and fades in 2–4 weeks; take it with food

Sexual side effectsCommon; tell me, they are treatable

Sweating, dry mouthCommon; tell me if bothersome, both can be treated

ConstipationFiber, fluids and exercise first

LiverAvoid heavy drinking; call for yellow eyes, dark urine or right-side belly pain

StoppingNever stop suddenly: dizziness, flu-like aches, brain zaps; we taper slowly

Suicidal thoughtsCall right away if new or worse, especially under 25

PearlsFull section

For mood and anxiety, 60 mg is where you stop: 120 mg adds nausea and sweating, not efficacy. Save 120 mg for fibromyalgia.

Hepatotoxicity (~1% ALT rise, rare hepatic failure) sets it apart. In liver disease or heavy drinking, use desvenlafaxine.

Small BP effect (label mean +0.5 mm Hg systolic, +0.8 diastolic), unlike venlafaxine's dose-dependent rise; the label still asks for BP checks.

Moderate CYP2D6 inhibitor: cut a co-prescribed TCA. Fluvoxamine and ciprofloxacin raise duloxetine; quitting smoking raises it too.

Painful depression: it treats the depression, not the pain specifically (effect size 0.115). For neuropathic pain a TCA or venlafaxine is as good.

Poor fits: urinary retention risk (BPH), narrow-angle glaucoma. For uncomplicated depression an SSRI or bupropion is cheaper and as effective.

Summary of this guide. Check the full sections before prescribing.

Photo credits

Cymbalta (duloxetine) 60 mg capsule beside a ruler: MilitaryAce ( Militaryace ), Public domain, Wikimedia Commons

Duloxetine (Cymbalta) 20 mg capsules in blister pack: User:MaksimTack, Public domain, Wikimedia Commons

Why Duloxetine Earns Its Place

Duloxetine is the SNRI to reach for when a patient's depression or anxiety comes with a body complaint (neuropathic pain, fibromyalgia, aching joints, chronic low back pain), or when you want an SNRI's noradrenergic reach without venlafaxine's blood-pressure liability. It is the most broadly FDA-labeled antidepressant in psychiatry, with five approved indications: mood, anxiety, and three distinct pain syndromes. It's generic, once-daily and easy to titrate, and mechanistically boring in the good way: it blocks serotonin and norepinephrine reuptake and does nothing else at the receptor level.

But sell it honestly. The "Depression Hurts" marketing built a reputation for painful depression that the data never earned: the analgesic effect size in depression is roughly 0.115 (p≈0.057, not significant), and much of what patients feel is placebo. Where duloxetine does help is narrower than the ad campaign claimed, and more useful: GAD (where a Lancet network meta-analysis ranked it among the most efficacious and best-tolerated agents on the highest-quality evidence), diabetic neuropathic pain and fibromyalgia (real, FDA-backed, though tricyclics often match or beat it), and depression in patients you want to keep off a drug that raises blood pressure.

Despite the name "SNRI," duloxetine is roughly 20:1 selective for serotonin over norepinephrine. It is more balanced than venlafaxine (120:1), but it is still, functionally, a serotonergic drug with a modest noradrenergic tail. Do not expect the "norepinephrine magic" (energy, motivation, focus) that the class name implies; no evidence supports a selective noradrenergic benefit.

Part 1: Indications

FDA-Approved Uses

• Major depressive disorder (MDD)
• Generalized anxiety disorder (GAD), including a pediatric GAD indication (ages 7+)
• Fibromyalgia
• Diabetic peripheral neuropathic pain
• Chronic musculoskeletal pain (studied in chronic low back pain and osteoarthritis)

Off-label: stress urinary incontinence (an approved indication in Europe and elsewhere, not in the US) and, weakly, OCD (sertraline is the better serotonergic choice there).

Where Duloxetine Is Most Useful

Depression with comorbid anxiety: a top-tier choice

Duloxetine holds an FDA GAD indication, and in the 2019 Lancet network meta-analysis of GAD pharmacotherapy it ranked among the most efficacious agents and among the best tolerated, on the highest-quality evidence of any antidepressant examined. When a patient's depression and anxiety are tangled together, duloxetine is a rational first move with evidence behind it. (Well-tolerated GAD comparators from the same analysis: escitalopram, venlafaxine XR, pregabalin. Quetiapine XR was most effective but poorly tolerated.)

Depression with a comorbid pain syndrome

This is duloxetine's marketing home turf, and the evidence is more modest than the campaign:

• Diabetic neuropathic pain: the NNT is about 5. Real, FDA-approved, but weaker than tricyclics or venlafaxine (NNT ≈ 3).
• Fibromyalgia: only the 120 mg dose separates cleanly from placebo (40.1% response at 120 mg vs 34% at 60 mg vs 23.7% placebo in a 520-patient, 6-month RCT). Rheumatologists still reach for amitriptyline first, given its longer track record and lower cost.
• Pain within depression (the "Depression Hurts" claim): the benefit is marginal, effect size 0.115, under a 1-point advantage on the Brief Pain Inventory, and no superiority over paroxetine across five head-to-head trials. Placebo delivers much of the apparent analgesia.

The hypertensive or cardiovascularly cautious patient

Duloxetine's advantage over venlafaxine is the size of the blood pressure effect. Venlafaxine causes dose-dependent diastolic hypertension (watch especially above 300 mg/day). Duloxetine's label carries a blood pressure warning too, and asks for a reading before starting and periodically after, but the measured effect is small: mean rises of 0.5 mm Hg systolic and 0.8 mm Hg diastolic, with no excess of sustained elevation. If you want SNRI pharmacology in someone with hypertension or cardiovascular risk, duloxetine is still the SNRI to pick.

Melancholic depression

Melancholia is the early-morning awakening, anorexia, psychomotor, ruminative-guilt phenotype that historically favored dual-mechanism drugs, and SNRIs are the reasonable second-line here when a tricyclic can't be tolerated. This is clinical inference more than hard trial data, but duloxetine and venlafaxine are the sensible SNRI choices.

Treatment-resistant depression (as a switch)

After an SSRI fails, switching to an SNRI is a standard second- or third-step move. Be honest about the ceiling: STAR*D showed that switching classes buys little; tolerability and side-effect fit, not mechanism, drive the real-world decision.

Where Duloxetine Is Not the Answer

• Uncomplicated depression: an SSRI or bupropion is cheaper, at least as effective, and (for bupropion) sexually neutral and weight-favorable. Duloxetine has no efficacy edge over SSRIs for depression alone.
• Liver disease or heavy alcohol use: the hepatotoxicity signal makes this the wrong SNRI (see Part 2 and Part 6).
• Urinary retention risk (e.g., BPH): the noradrenergic effect on the bladder sphincter can worsen retention, paradoxical given its overseas incontinence indication, but a real caution.

Part 2: Before You Start: Workup and Candidacy

Duloxetine needs far less workup than lithium, but it is not a "no-labs" drug the way an SSRI is. The one screen that matters is the liver.

Baseline assessment

No routine ECG, CBC, or electrolytes are required. Renal function is worth knowing (duloxetine is not recommended in severe impairment or ESRD), but it has no meaningful renal metabolism.

Who is a poor candidate?

• Liver disease or heavy alcohol use: avoid; use desvenlafaxine instead (glucuronidated, liver-sparing).
• Substantial urinary retention risk (BPH, prior retention).
• Narrow-angle glaucoma: rare but real; the noradrenergic effect can raise intraocular pressure.
• On an MAOI or within the washout window.
• Medically complex / heavy polypharmacy: the CYP2D6 inhibition and hepatic metabolism make desvenlafaxine the cleaner SNRI.

Part 3: How to Start and Dose

Formulations

Duloxetine comes as delayed-release capsules: 20, 30, 40, and 60 mg. It is generic and inexpensive. Take it with food or a snack, which aids absorption and blunts nausea. Once daily is standard; splitting BID (e.g., 30 mg twice daily) is a legitimate tolerability tool for nausea or dizziness.

Titration compared to venlafaxine

Duloxetine's schedule is simpler than Effexor XR's, with fewer dose steps and an easier climb to a therapeutic dose. That is a tangible, if modest, quality-of-life advantage for both prescriber and patient.

Dose Adjustments and Special Populations

• Hepatic impairment: avoid. Duloxetine is not recommended in patients with any hepatic insufficiency (cirrhosis cuts clearance to ~15% of normal, a roughly 5-fold rise in exposure), and it carries a hepatotoxicity signal.
• Renal impairment: not recommended in severe impairment or ESRD (CrCl <30 mL/min), where exposure roughly doubles; no adjustment for mild-to-moderate impairment.
• Poor CYP2D6 metabolizers (genetic, or on a strong 2D6 inhibitor): expect higher levels; titrate more cautiously.
• Smokers/cannabis users: CYP1A2 induction lowers duloxetine levels, relevant if they quit (levels rise; see Part 7).

Stopping and Switching

• Discontinuation: taper gradually. Duloxetine has a real discontinuation syndrome (dizziness, nausea, irritability, paresthesias, "brain zaps"). The 20 mg capsule helps step down; abrupt stops are the usual cause of trouble.

Part 4: Monitoring

Monitoring is light compared with lithium, but it is not zero.

No routine ECG, CBC, electrolytes, or drug levels are needed.

Thresholds to act on

• ALT rising / clinical hepatitis signs: stop duloxetine and evaluate. Do not wait for jaundice.
• New BP elevation: less expected than with venlafaxine, but check it if the patient reports symptoms.
• Hyponatremia symptoms (confusion, lethargy, falls, especially in the elderly): SNRIs, like SSRIs, can cause SIADH; check sodium if suspected.

Part 5: Side Effects and How to Manage Them

As with the SSRIs, most duloxetine side effects are early, dose-related, and either self-limited or manageable. The ones that make patients quit are nausea early on, sexual dysfunction long-term, and the discontinuation syndrome at the end. Start low, titrate up to the therapeutic dose, and manage side effects proactively.

Gastrointestinal: nausea

Nausea is the most common early complaint and the most common reason for early dropout. It is dose-related and usually resolves within 2–4 weeks.

Management:

• Take with food.
• Start at 30 mg, not 60, and titrate.
• Split the dose (30 mg BID) if needed.
• Reassure: this almost always fades, and getting through the first two weeks is usually enough.

Sexual dysfunction

Treatment-emergent sexual dysfunction (TESD) is common, and, as with all SSRIs/SNRIs, the directly-asked rate is far higher than what patients volunteer. In head-to-head data, duloxetine ran about 46% TESD vs paroxetine 61% (paroxetine worst) vs placebo ~29% over 8 weeks in previously unaffected patients; over a 34-week extension the rates converged (~39% duloxetine vs ~45% paroxetine vs ~35% placebo). Overall, duloxetine sits mid-pack: clearly better than paroxetine, roughly comparable to escitalopram, and no better than other SNRIs.

Management (in order of evidence):

• Switch to a sexually neutral agent if this is a dealbreaker: bupropion (best, no sexual side effects), mirtazapine, or trazodone. Do not switch to another SNRI; there's no advantage.
• PDE-5 inhibitors (sildenafil 50–100 mg) are robustly effective for antidepressant-induced ED in men and, in some data, women.
• Bupropion augmentation (SR 150–300 mg/day): inconsistent data, marginal, but a reasonable add-on if you want to keep the duloxetine.
• Vortioxetine has a slight TESD edge at low doses but not at therapeutic ones, so it isn't worth the cost/nausea trade for this alone.

Excessive sweating (diaphoresis)

A noradrenergic side effect, less prominent than with venlafaxine or levomilnacipran, but real.

Management:

• Terazosin 1–2 mg/day (alpha-blocker) or oxybutynin 5 mg 1–2×/day (anticholinergic).
• Glycopyrrolate off-label, but warn: anticholinergic sweat suppression impairs thermoregulation, a heat-stroke risk in hot conditions.

Dry mouth

Modest anticholinergic-like effect.

Management: OTC saliva substitutes, Biotene toothpaste/rinse, sugar-free gum. Counsel on increased caries risk; recommend regular dental care.

Constipation

From the noradrenergic tone.

Management:

• First-line: fiber, fluids (≥3 extra glasses/day), exercise.
• Docusate 100 mg up to TID; polyethylene glycol (Miralax) daily.
• Avoid chronic stimulant laxatives (senna, bisacodyl), which carry a risk of dependence and paradoxical worsening.

Drowsiness / fatigue

Generally mild for an SNRI (far less than a tricyclic), but it happens.

Management: shift to bedtime dosing. If persistent and the drug is otherwise working: modafinil 200–400 mg/day, armodafinil, or a psychostimulant.

Apathy / emotional blunting

The serotonergic "flatness" that patients describe as feeling less: less low, but also less everything. Dose-dependent.

Management: lower the dose (often enough), add bupropion or a stimulant, or switch class if it persists.

Weight

Mild on average, often near weight-neutral, sometimes modest gain over time (serotonergic effects on appetite/leptin). Not a mirtazapine-level problem.

Management: diet/exercise counseling; bupropion augmentation (the one antidepressant associated with weight loss); topiramate 100–150 mg/day (watch cognitive dulling); metformin for the metabolically vulnerable.

Other

• Headache, dizziness: common early, usually transient.
• Hyponatremia / SIADH: class effect, higher risk in the elderly; suspect it with new confusion or lethargy.
• Bleeding risk: serotonergic platelet inhibition raises GI-bleed risk, additive with NSAIDs/anticoagulants (less data than for SSRIs, but treat it as a real class effect).
• Mydriasis / narrow-angle glaucoma: rare, noradrenergic.

Part 6: Toxicity, Overdose, and the Boxed Warning

Hepatotoxicity

Practical protocol:

• Screen alcohol use before starting.
• Check baseline ALT and at least once during treatment.
• Avoid in liver disease and heavy drinkers: use desvenlafaxine instead (glucuronidated, minimal hepatic risk, minimal CYP involvement).
• Stop the drug at signs of hepatic injury (rising ALT, RUQ pain, jaundice, dark urine, unexplained fatigue). Don't wait it out.

Overdose

Duloxetine is far less lethal in overdose than a tricyclic. The concerns are serotonergic (serotonin syndrome, especially in combination or co-ingestion), seizures, and, at high doses, hepatotoxicity. Management is supportive, and an overdose needs an ED evaluation. There is no specific antidote.

Serotonin syndrome

The risk is real when duloxetine is combined with other serotonergic agents (MAOIs, contraindicated; linezolid and intravenous methylene blue, which the label says not to start duloxetine alongside; St. John's wort; other antidepressants; dextromethorphan). Duloxetine's own CYP2D6 inhibition can raise co-administered serotonergic drug levels, compounding risk. One old worry can be set aside: triptans + SNRIs are safe. Large studies (Orlova, JAMA Neurol 2018) refuted the historical FDA serotonin-syndrome warning.

Boxed Warning: Suicidality

Part 7: Drug Interactions

Duloxetine sits in the middle of the SNRI interaction spectrum: cleaner than venlafaxine in some respects, messier than desvenlafaxine, which is mostly glucuronidated.

Duloxetine as a CYP2D6 inhibitor

Duloxetine is a moderate CYP2D6 inhibitor (in the same family as paroxetine and fluoxetine, though generally regarded as less potent than those two). It raises levels of CYP2D6 substrates:

• Tricyclic antidepressants: can rise substantially; if combining, cut the TCA dose and monitor levels (TCAs have cardiac toxicity at high levels).
• Certain antipsychotics (aripiprazole, risperidone, brexpiprazole): raised levels, akathisia/EPS risk.
• Some beta-blockers, stimulants (amphetamines), and other 2D6 substrates: monitor.

Duloxetine's own metabolism (drugs/behaviors that affect its level)

Duloxetine is metabolized by CYP1A2 (primary) and CYP2D6.

• Strong CYP1A2 inhibitors (fluvoxamine, ciprofloxacin, other quinolones) markedly raise duloxetine levels; avoid or dose-reduce. Fluvoxamine is the classic offender.
• Smoking and cannabis induce CYP1A2 and lower duloxetine levels. Clinically meaningful within ~3 days; reverses over ~1 week. A patient who quits smoking (or switches to vaping/nicotine gum) can see duloxetine levels rise; watch for emergent side effects.

MAOIs: the absolute contraindication

• Never combine with an MAOI (serotonin syndrome, potentially fatal).
• Washout: 14 days after stopping an MAOI intended to treat a psychiatric disorder before starting duloxetine; 5 days after stopping duloxetine before starting one.
• 5-week washout when switching from fluoxetine to an MAOI (long half-life of norfluoxetine).

Additive-risk combinations

• Serotonergic agents (other antidepressants, linezolid, St. John's wort, dextromethorphan): serotonin syndrome risk.
• NSAIDs / anticoagulants / antiplatelets: additive GI-bleed risk via platelet serotonin depletion.
• Sympathomimetics (stimulants, decongestants): theoretical additive pressor effect, though duloxetine's own BP effect is minimal.

Part 8: Special Populations

Pregnancy

Drug-specific data in pregnancy are limited, but the class picture is reassuring. A large meta-analysis (Mezzacappa, JAMA Pediatr 2017) found that the apparent association between prenatal SSRI/SNRI exposure and autism largely attenuated after accounting for maternal mental illness, pointing to confounding by indication rather than a causal effect. Third-trimester exposure carries a small risk of poor neonatal adaptation (jitteriness, irritability, feeding/tone problems, self-limited) and rarely PPHN.

Framework: untreated depression in pregnancy has real risks of its own; decide case-by-case, minimize total exposures, and, when feasible, favor an agent the patient has previously responded to. Duloxetine is clearly preferable to paroxetine (older Category D, cardiac malformation concern) if the choice is between those two. If starting fresh in pregnancy, many clinicians default to a better-studied SSRI (sertraline), but duloxetine is not contraindicated.

Lactation

Limited data; duloxetine is excreted in breast milk in small amounts (relative infant dose is low). Sertraline is the best-studied and preferred antidepressant in lactation; duloxetine is probably acceptable but less characterized. If used, monitor the infant clinically.

Elderly (65+)

• Start low, go slow. 30 mg or lower to start.
• Effective in geriatric depression and GAD; for depression the label finds no added benefit above 60 mg, while for GAD in older adults it says patients may benefit from more than 60 mg (in 30 mg steps).
• No cardiac or anticholinergic toxicity the way a tricyclic has, a real advantage in this population.
• Watch: hyponatremia/SIADH (higher baseline risk in elderly), falls, and the hepatotoxicity issue if polypharmacy or hepatotoxic co-meds are present.
• If medically complex: desvenlafaxine is the cleaner SNRI (fewer interactions, liver-sparing).
• One geriatric study (mean age >70) showed duloxetine improved verbal learning/memory; vortioxetine edged it on processing speed, and both are cognitively benign choices.

Hepatic impairment

Avoid. This is duloxetine's contraindication population. Duloxetine depends on hepatic metabolism, which falls off in liver disease, and the drug already carries a hepatotoxicity signal. Use desvenlafaxine (mostly glucuronidated, and the safer choice here) or another class.

Renal impairment

Generally safe, with no major renal metabolism. In severe renal impairment (and ESRD) it is not recommended; exposure to the (inactive) metabolites rises. Mild-to-moderate impairment usually needs no adjustment. (Contrast with desvenlafaxine and venlafaxine, which need renal dose reductions.)

Pediatric / adolescent

• FDA-approved for pediatric GAD (ages 7+), which fills a niche.
• For pediatric depression, fluoxetine and escitalopram are the FDA-approved, preferred first-line agents; for pediatric OCD, sertraline. Duloxetine is not first-line for these.
• The boxed suicidality warning applies, as with all antidepressants under 25.

Part 9: Discontinuation

Stopping is where duloxetine bites, so do it carefully. Its half-life is short (~12 hours), which means plasma levels fall fast when doses are missed or the drug is stopped, and the result is a real, often miserable discontinuation syndrome. CANMAT 2023 puts duloxetine in the moderate-risk group for discontinuation symptoms, below venlafaxine and paroxetine (high risk), but a deliberate taper is still the rule.

How to stop

• Reduce by ~25–50% every 2–4 weeks, slowing further near the end (hyperbolic tapering: the last few milligrams are the hardest).
• The fluoxetine bridge: switch to fluoxetine (long half-life, self-tapering) and then taper the fluoxetine, an established psychopharmacology pearl for tough SNRI discontinuations, though it lacks RCT proof.
• Use the smaller capsule strengths (20, 30 mg) to make fine steps; for the final reductions some patients bead-count the delayed-release granules, which goes beyond the label (it says not to open the capsule and sprinkle its contents or mix them with liquids, because that might affect the enteric coating).
• Warn every patient at the start, not at the end: "If you ever want to come off this, we do it slowly and together. Stopping suddenly makes people feel awful, and it's avoidable."

Part 10: Duloxetine vs the Alternatives

vs SSRIs (escitalopram, sertraline, paroxetine). No efficacy edge for depression alone; an SSRI is usually the cheaper, cleaner first choice. Duloxetine is worth choosing over an SSRI only when you want (a) a pain-syndrome indication, (b) SNRI pharmacology for a partial SSRI responder, or (c) FDA-backed GAD coverage. On sexual dysfunction, duloxetine beats paroxetine and roughly ties escitalopram. On discontinuation, long-half-life fluoxetine is far gentler.

vs Venlafaxine (Effexor XR). This is the most important comparison between two SNRIs. For depression the two are close in efficacy; for neuropathic pain venlafaxine has the better NNT. Duloxetine wins on blood pressure (a minimal pressor effect vs venlafaxine's dose-dependent hypertension), on titration (simpler), and modestly on discontinuation risk (CANMAT 2023 rates duloxetine moderate and venlafaxine high). Venlafaxine wins on not carrying a hepatotoxicity flag and has a clearer dose-response curve you can push. In practice: duloxetine for the hypertensive/CV-cautious patient; venlafaxine when you want to reliably dose-escalate and the liver isn't a concern.

vs Desvenlafaxine (Pristiq). Similar efficacy. Desvenlafaxine's real edge is cleanliness: glucuronidated, minimal CYP450, no 2D6 inhibition, liver-sparing, making it the preferred SNRI for polypharmacy, hepatic disease, and medically complex patients. Its liability is a flat dose-response (50 mg ≈ 100 mg; can't meaningfully escalate). Duloxetine gives you dose flexibility (relevant for fibromyalgia) and pain labeling desvenlafaxine lacks.

vs Tricyclics (amitriptyline, nortriptyline). For neuropathic pain and fibromyalgia, TCAs are at least as effective (NNT ≈ 3 vs duloxetine 5) and remain rheumatology's first-line for fibromyalgia. Duloxetine wins decisively on safety and tolerability: no anticholinergic burden, no cardiac conduction toxicity, safe in overdose, far better in the elderly. The trade is efficacy-per-milligram (TCA) vs safety and ease (duloxetine).

vs Bupropion. Bupropion is the better choice for uncomplicated depression where you want to avoid sexual dysfunction and weight gain and add some activation. Duloxetine wins when there's anxiety (bupropion can worsen it) or pain (bupropion does nothing for pain).

vs Mirtazapine. Mirtazapine for the patient who needs sleep and appetite (and wants to avoid sexual dysfunction); duloxetine for the patient who can't afford the sedation and weight gain, or who needs pain coverage. Both are relatively SD-sparing.

vs Vortioxetine. Vortioxetine has a marginal cognitive edge (a few DSST points, clinically modest, on the order of a cup of coffee) and a slight low-dose sexual advantage that vanishes at therapeutic doses. Duloxetine is generic and cheap with less nausea. In most cases vortioxetine's benefits don't justify its cost and GI burden over duloxetine.

Why is duloxetine reasonably popular? It stays widely prescribed on the strength of the pain indications and the GAD data. Don't confuse market presence with superior efficacy: against SSRIs for mood alone, it has none.

Mechanism

Duloxetine inhibits presynaptic reuptake of serotonin and norepinephrine. It has no direct postsynaptic receptor agonism or antagonism, which is why its side-effect profile is "clean" for an older-style antidepressant (no antihistamine sedation, no anticholinergic load beyond mild dry mouth, no alpha-blockade). Despite the "SNRI" label it is ~20:1 selective for serotonin over norepinephrine, more balanced than venlafaxine (120:1) but still functionally a serotonergic drug with a noradrenergic supplement that becomes more relevant at higher doses. The noradrenergic component plausibly underlies its analgesic effect in neuropathic pain (descending pain-inhibitory pathways use both transmitters) and its sweating/constipation/urinary side effects. Metabolism is hepatic via CYP1A2 and CYP2D6, half-life ~12 hours.

For the SNRIs as a group, norepinephrine selectivity has never reliably predicted clinical benefit, and the promised "noradrenergic" gains in energy, focus, and motivation don't show up in the data. Treat duloxetine as a serotonergic antidepressant with useful pain labeling and BP neutrality, not as a fundamentally different mechanism from an SSRI.

The Bedside Cheat Sheet