Prescribing Citalopram

At a glance

The STAR*D SSRI: cheap, clean on interactions and gentle to stop. Its one real liability, QTc, deserves respect but not fear.

How to doseFull section

Comes as

Tablet10, 20, 40 mg (20 and 40 mg scored)

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

In shortThe label starts at 20 mg and tops out at 40 mg once daily, or 20 mg over age 60, with liver disease, in CYP2C19 poor metabolizers, or with a CYP2C19 inhibitor. Clinicians usually aim for 40 mg when none of those limits applies.

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.

Adultsmajor depressive disorder

StartFDA label20 mg once dailyIn practice20 mg once daily. In anxious or older patients, 10 mg for the first week, then 20 mg.

IncreaseFDA labelUp to a maximum of 40 mg once daily, no sooner than 1 week after startingIn practiceAt about week 4, raise to 40 mg if response is partial or absent and 20 mg is tolerated, unless capped at 20 mg (over 60, liver disease, CYP2C19).

Target doseFDA labelNo labeled doseIn practice40 mg a day for most adults. If 20 mg is tolerated with only partial benefit, go to 40 mg, unless capped at 20 mg (over 60, liver disease, CYP2C19).

MaximumFDA label40 mg once daily. Doses above 40 mg once daily are not recommended due to the risk of QT prolongation.In practiceThe 40 mg ceiling applies. Off-label A rare treatment-resistant patient may be taken above 40 mg with an ECG.

MaintenanceFDA labelNo labeled doseIn practiceContinue the dose that produced remission, usually 40 mg, or 20 mg in a capped patient. There is no separate lower maintenance dose.

Older adults (over 60)FDA labelMaximum 20 mg once daily for patients over 60In practiceStart at 10 mg, cap at 20 mg a day, and go slow

Liver impairmentFDA labelMaximum 20 mg once daily

CYP2C19 poor metabolizers or inhibitorsFDA labelMaximum 20 mg once daily for poor metabolizers and with a CYP2C19 inhibitor

Children and teensFDA labelSafety and effectiveness have not been established in pediatric patientsIn practiceOff-label and second-line; fluoxetine and escitalopram carry the pediatric depression indications

When to take itFDA labelOnce daily, with or without foodIn practiceMorning or evening; at night if it is sedating, in the morning if it is activating or disrupts sleep

Stopping and switchingFDA labelGradually reduce the dosage rather than stopping abruptly, whenever possible. At least 14 days between an MAOI antidepressant and Celexa, either way.In practiceAfter a short course, a modest taper over 2–4 weeks usually suffices. For long-term or higher-dose use, taper more gradually.

A patient on chronic omeprazole for reflux is capped at 20 mg, like an older patient.

Do not judge the trial before 4 weeks at 40 mg. Give a full trial 6–8 weeks before declaring failure.

IndicationsFull section

FDA-approved

Major depressive disorder (adults)

Off-label, evidence-based

GAD, panic disorder, social anxiety disorderOCD (the 40 mg ceiling limits it)PTSDAgitation in Alzheimer's dementia (CitAD, max 30 mg)

Boxed warningsFull section

Suicidality in patients <25Class warning; monitor closely in the first 2–4 weeks and at dose changes

ContraindicationsFull section

MAOIs (incl. linezolid, IV methylene blue)Absolute; 14 days between stopping either and starting the other

Baseline QTc >500 msChoose a different SSRI; stop or don't exceed if QTc >500 ms

MonitorFull section

Suicidality, side effectsWeeks 1–2, especially under 25

ResponseWk 4 (escalate to 40 mg if partial); full assessment at 6–8 wk

ECGQT-risk patients only: baseline, after reaching 40 mg, or when adding a QT drug. QTc >500 ms: stop

Potassium, magnesiumCardiac-risk patients, diuretic users, elderly

SodiumElderly or on diuretics; check if confused, lethargic or falling, mostly first ~2 wk

Sexual effects, weightAsk at every follow-up

No drug levels or routine labs in a healthy adult; no ECG for a young adult without QT risk.

Drug interactionsFull section

Drug-drug

MAOIsAbsolutely contraindicated: serotonin syndrome; 14-day washout each way

Ziprasidone, haloperidol, methadoneAdditive QTc; ECG if you must combine, correct K and Mg, consider another SSRI

Antiarrhythmics, macrolides, fluoroquinolonesAdditive QTc; check an ECG if combined

Omeprazole, esomeprazole, cimetidineRaise citalopram levels: cap at 20 mg/day; chronic omeprazole is the trap

Fluconazole, fluvoxamineStrong 2C19 inhibitors raise levels: cap at 20 mg/day

NSAIDs~4× upper GI-bleed risk (OR 4.25); add a PPI, but omeprazole means a 20 mg cap

Warfarin, antiplateletsElevated bleeding risk; consider a PPI in high-risk patients

Tramadol, linezolid, other serotonergicsSerotonin-syndrome risk, much lower than with MAOIs

TriptansRisk very low (0.6–2.3 cases per 10,000 person-years); no need to deny

CYP enzymes

CYP2C19Primary substratePoor metabolizers: AUC ~107% higher; inhibitors raise levels. Cap 20 mg/day

CYP3A4, 2D6Minor substrate contributions

Neither inhibits nor induces CYP enzymes to a clinically important degree.

Must counselFull section

Nausea, loose stoolsEarly and usually gone in 3–7 days; take it with food

Sexual side effectsCommon and lasting; tell me, a lower dose or bupropion can help

Feeling flat or numbTell me; it usually means the dose is too high

BleedingNSAIDs like ibuprofen raise stomach-bleed risk; ask me first

StoppingDon't stop suddenly; we taper to avoid dizziness and brain zaps

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

PearlsFull section

The two ways to fail a trial: stopping below 40 mg and stopping before 6 wk. STAR*D's mean effective dose was 41.8 mg.

20 mg cap if >60, hepatic impairment, 2C19 poor metabolizer, or on omeprazole, cimetidine, fluconazole or fluvoxamine. Chronic omeprazole is the trap.

QTc is real but small in outcome: large cohorts found no rise in sudden cardiac death. Screen the at-risk; if QT burden is high, sertraline is the usual pivot.

Clean on CYP2D6, 3A4 and 1A2: ideal in polypharmacy, and the best-evidenced SSRI-plus-bupropion pairing.

Not for bipolar depression as monotherapy: unopposed SSRIs can precipitate mood switching or rapid cycling. Use a mood stabilizer.

Overdose: QTc prolongation and torsades, more than other SSRIs and can be delayed. Needs ED evaluation with cardiac monitoring and serial ECGs.

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

Photo credits

Citalopram 20 mg and 40 mg tablets beside a US cent for scale: Elbreapoly, Public domain, Wikimedia Commons

Citalopram 20 mg film-coated tablets, box and blister: Fimpelman, CC BY 3.0, Wikimedia Commons

Citalopram (Citalec) 20 mg, box and blister: Pavel Dušek, CC BY-SA 4.0, Wikimedia Commons

Why Citalopram Still Matters

Citalopram is the SSRI behind the largest antidepressant trial ever conducted. When the NIMH designed STAR*D and needed one drug for the mandatory first step in 4,041 real-world depressed patients, it picked citalopram, for reasons that still make it a sound first-line choice today: minimal drug interactions and a discontinuation risk that CANMAT 2023 rates moderate, below paroxetine and venlafaxine. It is cheap, generic, once-daily, and boring in the way you want a drug to be. It does its job without inducing or inhibiting the CYP450 enzymes that make fluoxetine and fluvoxamine a headache in anyone on polypharmacy.

Then, in 2011, the FDA issued a warning about dose-dependent QTc prolongation, capped the dose at 40 mg (20 mg in the elderly and in poor metabolizers), and citalopram's reputation took a hit it has never fully recovered from. Escitalopram, its own S-enantiomer, was marketed as "the son of Celexa," and inherited the franchise with half the QTc effect and a marketing budget citalopram lacked.

The QTc warning describes real pharmacology, but its clinical consequences have turned out far smaller than the warning implied. Multiple large retrospective cohorts (Tennessee Medicaid, VA) found no increase in sudden cardiac death with high-dose citalopram versus other SSRIs, and the VA's forced deprescribing after the warning was associated with more hospitalizations and deaths, not fewer arrhythmias.

Part 1: Indications

FDA-Approved Use

• Major depressive disorder (adults)

That is its only FDA indication. Everything else is off-label but well supported, because SSRIs as a class are broadly effective anxiolytics and antidepressants, and citalopram behaves like its peers.

Evidence-Based Off-Label Uses

• Generalized anxiety disorder, panic disorder, social anxiety disorder: SSRIs are first-line; citalopram works as well as its class-mates.
• OCD: SSRIs match clomipramine for efficacy with far better tolerability; OCD typically needs the higher end of dosing and a longer trial (10–12 weeks).
• PTSD: reasonable off-label option; sertraline and paroxetine carry the formal indications, but the class effect applies.
• Agitation in Alzheimer's dementia (BPSD): a useful niche with trial evidence behind it. In the CitAD trial (Porsteinsson, JAMA 2014; 186 non-depressed Alzheimer's patients), citalopram 10 mg titrated to a max of 30 mg significantly reduced agitation versus placebo. Mind the lower ceiling: these are elderly patients, and QTc and cognitive worsening at 30 mg were real signals in that study.

Who Citalopram Is Especially Good For

• The polypharmacy patient. Because citalopram neither induces nor inhibits CYP450 enzymes to any clinically meaningful degree, it is one of the safest antidepressants to layer onto a complex medication list: cardiac drugs, antiepileptics, transplant meds, oncology regimens. This is its defining advantage.
• The patient you may need to stop later. Its discontinuation risk is moderate (CANMAT 2023), lower than paroxetine's or venlafaxine's.
• The older adult (with the caveats below): alongside sertraline and escitalopram, citalopram is a preferred SSRI in geriatric depression for its clean interaction profile and lack of anticholinergic burden.
• The patient who needs bupropion augmentation. Citalopram plus bupropion is a clean, well-tolerated pairing (no CYP tangle), and it has among the best evidence of the SSRI-plus-bupropion combinations.

Who Citalopram Is Not For

• Bipolar depression as monotherapy. STAR*D excluded bipolar disorder because unopposed SSRIs can precipitate mood switching or accelerate rapid cycling. If you must use an antidepressant in bipolar depression, do it under cover of a mood stabilizer.
• Anyone with baseline QTc >500 ms, or on multiple other QT-prolonging drugs: choose a different SSRI (sertraline is the usual pivot).
• Complicated grief. Citalopram alone did not beat placebo; grief-focused psychotherapy is the effective treatment. (The trial was also hobbled by a mid-study forced dose reduction, but the practical message stands: don't reach for citalopram as a grief drug.)

Part 2: Before You Start

Citalopram requires no routine baseline labs in a healthy adult. The workup is short and mostly about identifying the small group in whom QTc matters.

The Pre-Start Checklist

QT-risk factors to tally: older age, female sex, structural heart disease, bradycardia, hypokalemia, hypomagnesemia, congenital long-QT, and concurrent QT-prolonging drugs (many antipsychotics, methadone, high-dose ondansetron, certain antibiotics/antiarrhythmics). A young, healthy adult with none of these needs neither an ECG nor much worry about the ceiling.

Part 3: How to Start and Dose

Formulation

Citalopram comes as tablets in 10, 20, and 40 mg (the 20 and 40 mg tablets are scored) and as an oral solution, 10 mg/5 mL (2 mg/mL citalopram base), which is useful for fine titration, for the small decrements of a slow taper, and for patients who cannot swallow tablets. Citalopram is a racemic mixture: a 50/50 blend of R- and S-enantiomers, of which only the S-enantiomer (escitalopram) is pharmacologically active at the serotonin transporter (the S-form is far more potent at SERT). So 20 mg of citalopram is roughly equivalent to 10 mg of escitalopram.

Dose Adjustments and Special Populations

• Geriatric (>60): start 10 mg, cap at 20 mg/day. Older patients also concentrate the other SSRI hazards (hyponatremia, falls, bleeding), so the low ceiling does double duty.
• Hepatic impairment: reduced clearance raises drug levels and QT risk, so cap at 20 mg/day.
• CYP2C19 poor metabolizers / CYP2C19 inhibitors: poor metabolizers run citalopram C_max ~68% and AUC ~107% higher, so genetics or a 2C19 inhibitor (omeprazole/esomeprazole, cimetidine, fluconazole, fluvoxamine) both drop the ceiling to 20 mg/day.
• Renal impairment: mild-to-moderate impairment reduces clearance only ~17%, so no dose adjustment is needed. Citalopram has not been studied in severe impairment (CrCl <20 mL/min); use with caution and monitor.
• Pediatric: not FDA-approved. Fluoxetine (from age 8) and escitalopram (from age 12) carry the pediatric depression indications; citalopram is off-label and second-line here.
• Pregnancy / lactation: no defined dose change. Citalopram passes into breast milk at low levels, is generally compatible with breastfeeding, and is a reasonable choice in pregnancy; the decision is whether to use it, not how to dose it (see Part 8).

Onset and Trial Length

• Serotonin transporter blockade is immediate, and pooled SSRI trial data show separation from placebo by the end of week 1, with improvement continuing at a decreasing rate for at least 6 weeks (the slow build is thought to reflect 5-HT1A autoreceptor desensitization and downstream BDNF/synaptic remodeling, not simply the acute rise in synaptic serotonin).
• Steady state: ~1 week (half-life ~35 hours, long enough for comfortable once-daily dosing and forgiving of a missed dose).
• Do not judge the trial before 4 weeks at 40 mg, and give a full trial 6–8 weeks before declaring failure. The most common prescribing error is bailing early.

Part 4: Monitoring

Citalopram needs little routine monitoring in a healthy adult: no drug levels, no mandatory labs. Spend your attention where it pays off.

The Monitoring Schedule

Targeted Checks (Not for Everyone)

• ECG: only in QT-risk patients, at baseline, after reaching 40 mg, or when adding another QT drug. Discontinue (or don't exceed) citalopram if QTc >500 ms. For a healthy young adult, routine ECG is unnecessary.
• Sodium: check in older adults if any confusion, lethargy, dizziness, or new falls: SSRI hyponatremia most often appears within the first ~2 weeks.
• Bleeding: no lab, but stay alert in patients on NSAIDs/anticoagulants; consider a PPI, which lowers upper GI bleed risk substantially.

Part 5: Side Effects and How to Manage Them

As with any SSRI, early side effects are usually transient and warrant reassurance, while the durable ones are sexual dysfunction and emotional blunting, both dose-related and manageable. On balance, citalopram is one of the better-tolerated SSRIs.

Early / Transient (First 1–2 Weeks)

Nausea, loose stools, headache, jitteriness, transient insomnia or sedation. These typically resolve within 3–7 days.

• Take with food for nausea.
• Move the dose (evening if sedating, morning if activating).
• Reassure: most patients who quit in week 1 quit over side effects that would have faded.

Gastrointestinal

Citalopram is more prone to diarrhea than average (odds ratio ~1.64 across antidepressants) but is less likely than SNRIs to cause constipation, which helps its tolerability.

• Persistent diarrhea: dose with food, consider PRN loperamide, or switch agents if intolerable.

Sexual Dysfunction

The most common lasting SSRI side effect (~50–70% across the class): decreased libido, delayed or absent orgasm, erectile difficulty, genital numbing. Often under-reported unless you ask directly.

• Ask at every follow-up: patients rarely volunteer it and it drives silent non-adherence.
• Lower the dose if efficacy allows (often helps without losing benefit).
• Switch agent: not every SSRI produces the same profile in the same person; if two SSRIs both cause it, consider a non-SSRI.
• Bupropion: as a switch or an add-on. It has the least sexual dysfunction and can offset the SSRI effect.
• Sildenafil/tadalafil for the erectile component.

Emotional Blunting

A gray, flattened, "zombie" feeling with loss of positive as well as negative emotion. This is a signal of too-high a dose, not an expected therapeutic state.

• Lower the dose. If the patient can't find a dose that treats the depression without blunting, that's a reason to change drugs.

Weight

SSRI-associated weight gain is usually modest and partly reflects recovered appetite. Citalopram is metabolically neutral relative to mirtazapine and TCAs.

• Diet/exercise counseling; consider a more weight-neutral agent (or bupropion) if it becomes a dealbreaker.

Sleep / Energy

Usually mild. If activating, dose in the morning; if sedating, dose at night. Persistent fatigue: rule out relapse and hypothyroidism before blaming the drug.

Other

• Sweating, mild tremor: usually minor and dose-related.
• Hyponatremia (see Part 6): mostly older adults.
• Bruising / bleeding tendency: via platelet serotonin depletion.
• Sedation and cognitive fog are less a citalopram problem than a paroxetine problem; if a patient is foggy on citalopram, check the thyroid and the dose before assuming the drug.

Part 6: Overdose, Toxicity, and the QTc Question

Overdose

SSRIs are, as a class, relatively safe in overdose compared with TCAs and MAOIs, a meaningful advantage in a depressed, potentially suicidal population. The citalopram-specific caveat is QTc prolongation and the risk of torsades in large overdoses, which is more pronounced than with other SSRIs and can be delayed. Any significant citalopram overdose warrants ED evaluation with cardiac monitoring and serial ECGs. As with any SSRI, watch for serotonin syndrome, especially with co-ingestants.

Serotonin Syndrome

Agitation, confusion, autonomic instability (tachycardia, hyperthermia, diaphoresis), hyperreflexia, clonus, rigidity. Risk rises when citalopram is combined with MAOIs (absolutely contraindicated), including linezolid and intravenous methylene blue, which act as MAOIs (the label says not to start citalopram in a patient being treated with either, and to stop citalopram before starting either one if that treatment is needed), and to a much lesser degree with tramadol, triptans, or other serotonergics. Management: stop the offending agents, supportive care, cyproheptadine in severe cases. In practice, the triptan risk is very low, on the order of 0.6–2.3 cases per 10,000 person-years, and a migraineur on an SSRI who occasionally uses a triptan does not need to be denied either.

The QTc Warning: What It Means and What It Doesn't

This is citalopram's defining safety issue, so be precise about it:

• The effect is real and dose-dependent. Citalopram 60 mg prolongs QTc by roughly 18.5 ms; escitalopram 30 mg by about half that (~10.7 ms). Citalopram is the most QT-prolonging SSRI.
• The FDA response (2011, softened 2012): don't exceed 40 mg generally, 20 mg in the elderly/hepatic/poor-metabolizer/CYP2C19-inhibitor groups; stop if QTc >500 ms.
• But the clinical outcomes have not matched the warning's alarm. Large retrospective cohorts, Ray (Tennessee Medicaid, 54,220 high-dose SSRI users) and Zivin (VA), found no significant increase in sudden cardiac death or ventricular arrhythmia with high-dose citalopram versus other SSRIs. And when the VA forced roughly 35,000 veterans to lower their dose after the warning, the result was a rise in all-cause hospitalizations and deaths with no decline in arrhythmias.

Part 7: Drug Interactions

Citalopram's low interaction burden is one of its best features, but it is not zero, and the interactions it does have cluster around two axes: CYP2C19 (which changes its own levels) and QTc (which changes its safety).

The Interactions That Raise Citalopram Levels (Cap at 20 mg)

Citalopram is metabolized primarily by CYP2C19. 2C19 inhibitors raise its levels and, with them, the QTc risk:

• Omeprazole / esomeprazole (PPIs)
• Cimetidine (H2 blocker)
• Fluconazole, fluvoxamine, and other 2C19 inhibitors

When these are co-prescribed (or the patient is a genetic poor 2C19 metabolizer), hold the ceiling at 20 mg. A patient on chronic omeprazole is functionally in the same bin as an elderly patient.

The Interaction That Matters Most Clinically: Additive QTc

Combining citalopram with other QT-prolonging drugs (antipsychotics such as ziprasidone, haloperidol, thioridazine, methadone, class IA/III antiarrhythmics, certain macrolide/fluoroquinolone antibiotics, high-dose IV ondansetron) stacks the QTc effect. This is the interaction to actively screen for. Check an ECG if you must combine, correct hypokalemia/hypomagnesemia, and consider a non-citalopram SSRI if the QT burden is high.

Bleeding

SSRIs plus NSAIDs raise upper GI bleed risk substantially (pooled odds ratio 4.25, 95% CI 2.82 to 6.42, for the combination in a 2014 meta-analysis); SSRIs plus warfarin/antiplatelets also elevate it. Co-prescribe a PPI in high-risk patients; acid suppression lowers the bleeding risk. There is a catch: omeprazole both protects against the bleed and raises citalopram levels, so if you use it for GI protection, keep the citalopram at 20 mg.

MAOIs: Absolute Contraindication

Never co-administer. The label asks for at least 14 days in either direction between citalopram and an MAOI antidepressant (from the MAOI to citalopram, and from citalopram to the MAOI, given its ~35-hour half-life).

What Citalopram Does Not Meaningfully Do

• It does not inhibit or induce CYP2D6, 3A4, or 1A2 to a clinically important degree, and that clean profile is the main reason to choose it. Unlike fluoxetine (potent 2D6/2C19 inhibitor, raises TCAs, aripiprazole, risperidone, and can block activation of prodrugs like tamoxifen, tramadol, and codeine; effects linger for weeks) or fluvoxamine (potent 1A2/3A4 inhibitor, dangerous with clozapine, theophylline, tizanidine), citalopram leaves other drugs' levels practically untouched.

Part 8: Special Populations

Pregnancy

The mainstream position is that for moderate-to-severe depression, treating usually beats not treating, because untreated antenatal depression carries real fetal and maternal risk, partly through behavioral pathways (missed prenatal care, poor nutrition, substance use) and partly through relapse and postpartum depression.

• First-trimester teratogenicity is low; the class signal for cardiac septal defects is small and most concentrated with paroxetine, which is generally avoided in pregnancy.
• Third trimester: a self-limited neonatal adaptation syndrome (jitteriness, tremor, feeding/respiratory difficulty) occurs in a minority of exposed newborns, and there is a small absolute increase in persistent pulmonary hypertension of the newborn. Neither justifies reflexive discontinuation of an effective medication in a woman who needs it.
• Escitalopram is sometimes preferred over citalopram in pregnancy (S-enantiomer only, lower total exposure), but citalopram is a reasonable, well-studied choice, especially if a woman is already stable on it.
• Practical rule: individualize with the patient and OB, don't stop a working antidepressant out of reflex, and if you continue, plan neonatal observation.

Lactation

Citalopram is excreted into breast milk in low amounts and is generally considered compatible with breastfeeding; sertraline and paroxetine have the lowest milk levels if you're choosing de novo, but an infant of a stably treated mother rarely needs more than routine pediatric observation.

Elderly (>60)

• Cap at 20 mg/day (QTc safety).
• Start low (often 10 mg) and go slow.
• Hyponatremia is the population-specific hazard, highest in older adults, usually within the first 2 weeks; check sodium if confused, lethargic, or falling.
• Also watch bleeding risk (screen NSAIDs/anticoagulants), falls/fractures (SSRIs modestly reduce bone density), and stack QT drugs cautiously.
• The upside: citalopram's clean interaction profile and lack of anticholinergic load make it a preferred SSRI in geriatric depression.

Renal and Hepatic Impairment

• Renal: no dose adjustment in mild-to-moderate impairment, where oral clearance falls only ~17%; citalopram has not been studied below a creatinine clearance of 20 mL/min, so use caution and monitor there.
• Hepatic: cap at 20 mg; reduced clearance raises levels and QTc risk.

Children and Adolescents

• Fluoxetine is the preferred first-line pediatric SSRI (best studied, FDA-approved for depression down to age 8). Citalopram has some supporting evidence but is second-line.
• The boxed suicidality warning (ages <25) is real to monitor: in the label's pooled placebo-controlled trials, antidepressant treatment added 14 cases of suicidal thoughts or behaviors per 1,000 patients under 18 and 5 per 1,000 aged 18 to 24. Monitor closely in the first 2–4 weeks, through the first few months and at each dose change, as the label advises. Citalopram is not approved for pediatric patients, which is why fluoxetine and escitalopram come first.

Part 9: Discontinuation

CANMAT 2023 puts citalopram in the moderate-risk group for discontinuation symptoms, with escitalopram and sertraline; paroxetine and venlafaxine are the high-risk drugs, and fluoxetine is low. Its ~35-hour half-life gives a gentler taper than paroxetine's shorter one, though not the built-in self-taper of fluoxetine.

• Discontinuation syndrome (when it occurs): dizziness, nausea, fatigue, flu-like malaise, irritability, and the characteristic "brain zaps" (brief, non-painful electric-shock sensations). Roughly 60% of patients have no withdrawal, ~35% mild-to-moderate, ~5% severe.
• Risk factors for a rougher stop: high dose, long duration (years), abrupt cessation.
• How to taper: for short courses (a few months), a modest taper over 2–4 weeks usually suffices. For long-term or higher-dose users, taper more gradually, hyperbolically, taking smaller and smaller decrements as you approach zero (e.g., 40 → 20 → 10 → 5 → stop, using the oral solution for fine steps if needed). The iterative rule: if withdrawal symptoms emerge, go back to the last comfortable dose and taper more slowly. With patience this almost never fails.
• Rapid discontinuation needed? Citalopram is a moderate-risk drug here, so if you need a clean abrupt stop, fluoxetine's long half-life makes it the safer bridge.

Part 10: Citalopram vs the Alternatives

• vs Escitalopram (Lexapro): escitalopram is citalopram's active S-enantiomer. It offers a marginal (~5–10%) efficacy edge in equipotent head-to-head trials, possibly slightly faster onset, and about half the QTc prolongation, which matters most. Two population studies found more cardiac arrests/serious arrhythmias with citalopram than escitalopram. If cost is no object and QT is any concern, escitalopram is the cleaner choice. Citalopram remains fully valid, especially where the generic price or formulary favors it. To switch: add escitalopram at 5 mg and titrate to roughly half the citalopram dose over 2–4 weeks while tapering the citalopram.
• vs Sertraline: comparable efficacy; sertraline has no QTc ceiling and is a common pivot when QT is the concern, at the cost of somewhat more diarrhea. Both are geriatric- and pregnancy-friendly.
• vs Fluoxetine: fluoxetine is more activating (good for the fatigued patient, bad for the insomniac), has a long half-life (built-in taper, but a 5-week MAOI washout), and is a potent CYP inhibitor, the opposite of citalopram's clean interaction profile. Fluoxetine is preferred in pediatrics.
• vs Paroxetine: avoid paroxetine where you can: worst sexual dysfunction, worst withdrawal, anticholinergic, cognitive fog, pregnancy cardiac signal. Citalopram beats it on nearly every tolerability axis.
• vs Fluvoxamine: fluvoxamine's potent 1A2/3A4 inhibition makes it interaction-laden; reserved mostly for OCD. Citalopram is far friendlier in polypharmacy.
• vs SNRIs (venlafaxine, duloxetine): SNRIs may edge citalopram at high doses in some analyses but add blood-pressure elevation (venlafaxine) and, with venlafaxine, a higher risk of discontinuation symptoms (high risk in CANMAT 2023; citalopram and duloxetine are both moderate). STAR*D found no efficacy advantage switching citalopram non-remitters to venlafaxine.
• vs Bupropion: roughly equal antidepressant efficacy, even with comorbid anxiety. Bupropion wins on sexual side effects (it's sexual-sparing) and pairs cleanly with citalopram as an augment, the best-evidenced SSRI-plus-bupropion combination.
• vs TCAs / MAOIs: citalopram is far better tolerated and vastly safer in overdose; TCAs and MAOIs are later-line, for true treatment resistance.

Mechanism

Citalopram is a highly selective serotonin reuptake inhibitor: it blocks the serotonin transporter (SERT), leaving more serotonin in the synapse, with negligible noradrenergic, dopaminergic, histaminergic, or anticholinergic activity, so it's clean on sedation, weight, and cognition relative to older agents. Transporter blockade is immediate, while the clinical effect builds over the first several weeks, attributed to gradual desensitization of 5-HT1A autoreceptors and downstream BDNF-driven synaptic remodeling rather than to the acute rise in synaptic serotonin. It is a racemate; only the S-enantiomer (escitalopram) is active at SERT, with the R-enantiomer largely inert and possibly mildly antagonistic to the S-form's effect, the pharmacologic rationale behind marketing the purified S-enantiomer separately. Half-life is ~35 hours; metabolism is primarily hepatic via CYP2C19 (with minor 3A4/2D6 contributions), and it neither meaningfully induces nor inhibits CYP enzymes.

The Bedside Cheat Sheet