Obsessive-Compulsive Disorder
Clinical Snapshot
Obsessive-compulsive disorder (OCD) is classified separately from the anxiety disorders in DSM-5-TR, alongside a family of related conditions that includes body dysmorphic disorder, hoarding disorder, trichotillomania (hair-pulling disorder), and excoriation (skin-picking) disorder.[1] Obsessions are recurrent, intrusive thoughts, images, or urges that provoke marked anxiety and are difficult to suppress or ignore; compulsions are repetitive behaviours (washing, checking, ordering) or mental acts (counting, silently repeating a phrase) performed to neutralize the distress an obsession causes or to prevent a feared outcome, even though the connection between the compulsion and the feared outcome is often unrealistic. Mean age of onset is in the early twenties, with a substantial proportion of cases beginning in childhood or early adolescence; onset tends to be earlier in males, while the disorder overall is more common in females.[2] In severe, inadequately treated OCD, rituals can occupy many hours of the day and become severely disabling — but the reverse is equally true: correctly dosed and adequately durated treatment produces real, durable symptom reduction for most patients, which makes getting the dose and duration right one of the highest-yield things a pharmacist can influence in this condition.
Recognize the Condition
OCD presents along a small number of recognizable symptom themes, most patients experiencing more than one. Recognizing the theme helps distinguish OCD from superficially similar presentations (see the differential table in Assessment & Diagnosis) and helps a pharmacist understand why a patient's ritual makes internal sense to them even when it appears irrational to an outside observer.
Common OCD symptom dimensions
Most patients have obsessions and compulsions from more than one dimension.
Contamination / washing
Obsessive fear of contamination (germs, illness, chemicals, bodily fluids) driving excessive washing, showering, or cleaning rituals, and avoidance of "contaminated" objects or places.
Harm / checking
Intrusive fear of causing harm through carelessness (leaving the stove on, hitting a pedestrian while driving, leaving a door unlocked) driving repeated checking behaviours.
Symmetry / ordering
A need for objects, actions, or numbers to feel "exactly right," driving arranging, counting, or repeating rituals until a sense of completeness is reached.
Unacceptable / taboo thoughts
Intrusive, ego-dystonic thoughts or images with sexual, violent, or religious/moral content that the patient finds distressing and contrary to their own values, often driving mental rituals (reviewing, praying, seeking reassurance) rather than visible behaviours.
Insight specifier
DSM-5-TR requires specifying the patient's insight into their OCD beliefs at the time of assessment: good or fair insight (recognizes the obsessive-compulsive beliefs are definitely or probably not true), poor insight (thinks the beliefs are probably true), or absent insight/delusional beliefs (completely convinced the beliefs are true). Insight can fluctuate over the course of the illness and does not by itself indicate a primary psychotic disorder — but very poor or absent insight changes the differential and the counselling approach (see Assessment & Diagnosis).[1]
Tic-related specifier and pediatric-onset presentations
DSM-5-TR also specifies whether OCD is tic-related (a current or past history of a tic disorder), which is more common in males and in childhood-onset OCD. A distinct, more controversial pattern in children is pediatric autoimmune neuropsychiatric disorders associated with streptococcus (PANDAS) — an abrupt, dramatic onset or exacerbation of OCD symptoms temporally linked to a streptococcal infection. Screen for a recent streptococcal infection when a child presents with an unusually sudden-onset OCD picture, though the entity remains debated in the literature.[2]
Risk Factors
- Family history of OCD or a related disorder (body dysmorphic disorder, hoarding disorder, tic disorder) in a first-degree relative.
- Personal or family history of a tic disorder, particularly for childhood-onset, tic-related OCD.
- Female sex (OCD is somewhat more common in females overall, though onset tends to occur earlier in males).
- Perinatal and postpartum period — new-onset or worsening OCD, particularly harm-related obsessions about the infant, is common in this window.
- Head injury or a neurocognitive disorder, which can rarely trigger obsessive-compulsive symptoms.
- New use of a stimulant, a dopamine agonist (e.g., pramipexole), or a serotonin-dopamine antagonist (e.g., clozapine) — screen medication history for these before assuming a primary psychiatric cause.
- Recent streptococcal infection in a child with abrupt-onset symptoms (possible PANDAS) — a debated but still relevant history question.
- Comorbid anxiety disorder, depression, or another OCD-spectrum condition.
Red Flags & Refer
Refer or escalate for any of the following:
- Suicidal ideation, intent, or a plan — actively screen for this at every assessment and every SSRI dose change, not only at diagnosis. All SSRIs and SNRIs carry a boxed warning for increased risk of suicidal thinking and behaviour in patients under 25, and the risk is highest in the first weeks after starting or changing dose — this is a counselling point to give proactively, not just a chart flag.
- Severe functional impairment — inability to work, attend school, leave the house, or manage basic self-care because of rituals or avoidance.
- Comorbid psychotic features, or absent-insight/delusional-level conviction in the obsessive beliefs that raises genuine diagnostic uncertainty with a primary psychotic disorder — needs psychiatric assessment rather than routine OCD management.
- Postpartum OCD with harm-related obsessions severe enough that the patient is refusing to care for or be alone with the infant — this needs urgent psychiatric consultation, not reassurance alone; while people with these obsessions are not at higher risk of actually harming their child than the general population, the distress itself can be severe and disabling.
- Hoarding severe enough to create a fire, structural, sanitation, or fall hazard in the home, or to trigger eviction/child-welfare/adult-protective-services involvement — this is a safety issue requiring a coordinated response beyond standard OCD pharmacotherapy.
- New or worsening obsessive-compulsive symptoms with a plausible organic trigger (head injury, new neurologic signs, new dopaminergic or stimulant medication) — investigate and address the underlying cause rather than treating symptomatically as primary OCD.
Assessment & Diagnosis
Differentiating OCD from commonly confused presentations
| Feature | OCD | Generalized anxiety disorder | Illness anxiety disorder | Body dysmorphic disorder | Poor-insight OCD vs. a primary psychotic disorder |
|---|---|---|---|---|---|
| Core content | Intrusive, unwanted, ego-dystonic obsessions across variable themes, neutralized by compulsions | Diffuse, excessive worry about everyday real-life concerns (finances, health, family) | Preoccupation with having or acquiring a serious undiagnosed illness, despite medical reassurance | Preoccupation with a perceived defect in physical appearance that is not observable or appears slight to others | Fixed, false beliefs (delusions) plus other psychotic features (hallucinations, disorganization) |
| Insight | Usually retained (recognizes the thoughts/behaviours as excessive), but can range to absent/delusional | Retained — recognizes the worry is excessive but cannot control it | Variable, often retained | Often poor — many patients are convinced the perceived defect is real and obvious | Absent by definition — no recognition that the belief is false |
| Associated behaviour | Ritualized compulsions specifically linked to neutralizing a specific obsession | No compulsive rituals; behaviour is generalized avoidance or reassurance-seeking | Repeated body checking, symptom-checking, doctor-shopping | Mirror checking or avoidance, camouflaging, skin-picking, reassurance-seeking about appearance | Behaviour follows the delusional system, not a recognizable obsession-compulsion pair |
| Distinguishing clue | The patient can usually describe the specific obsession the compulsion is meant to neutralize | Worry is about real-life circumstances, not an intrusive, senseless thought | Focus is specifically on having a disease, not on appearance or a discrete intrusive thought | Focus is specifically on a perceived appearance flaw | Look for hallucinations, disorganized thought/behaviour, or a broader delusional system beyond the obsessive content |
History
- Nature and onset of obsessions and compulsions, and the extent of resulting distress, time consumed, and functional disability at work, school, and home.
- Related difficulties: symptom-related beliefs, avoidance behaviour, and family/partner accommodation (family members participating in or facilitating rituals to reduce the patient's distress) — accommodation maintains and can worsen symptoms and is an important target for CBT.
- Comorbid medical or psychiatric conditions. When comorbid depressive symptoms are present, distinguish a true comorbid mood disorder from secondary depression driven by OCD itself, which commonly remits spontaneously as OCD symptoms improve.[2]
- Screen medication and substance history for triggers: new stimulant use, dopamine agonists (e.g., pramipexole), and serotonin-dopamine antagonists (e.g., clozapine) have all been associated with obsessive-compulsive symptoms.[2]
- In children with abrupt-onset symptoms, ask about a recent streptococcal infection (possible PANDAS).
DSM-5-TR diagnostic criteria
- Presence of obsessions, compulsions, or both, as defined above.
- The obsessions/compulsions are time-consuming (commonly more than 1 hour per day) or cause clinically significant distress or impairment in social, occupational, or other important functioning.
- The symptoms are not attributable to a substance or another medical condition.
- The symptoms are not better explained by another mental disorder.
Insight (good/fair, poor, or absent/delusional) and tic-relatedness are recorded as specifiers, not separate diagnostic requirements — a patient with poor insight still has OCD, not a primary psychotic disorder, provided the presentation otherwise fits (see the differential table above).[1]
Standardized severity measurement — Yale-Brown Obsessive Compulsive Scale (Y-BOCS)
The Y-BOCS is the standard instrument for rating OCD severity and tracking treatment response.[3] It is a clinician-administered, semi-structured interview, not a self-scored questionnaire — a trained rater first reviews a symptom checklist to identify the patient's specific obsessions and compulsions, then rates 10 items (5 on obsessions, 5 on compulsions: time occupied, interference, distress, resistance, and control) each from 0 (none) to 4 (extreme) against defined anchor descriptions, for a total score of 0-40.
| Total score | Severity band |
|---|---|
| 0-7 | Subclinical |
| 8-15 | Mild |
| 16-23 | Moderate |
| 24-31 | Severe |
| 32-40 | Extreme |
Because scoring requires a trained rater applying clinical judgment to open-ended interview responses against anchor descriptions — not a fixed patient-completed point-sum like the GAD-7 or PHQ-9 — the Y-BOCS is not suitable for a self-serve interactive calculator on this page; use the table above only as an orientation to how severity is categorized, and use the validated instrument itself (or a brief validated alternative such as the 6-item Brief Obsessive Compulsive Scale) for actual clinical scoring.[3]
When testing is not indicated
Routine neuroimaging, EEG, or laboratory testing is not indicated for a typical OCD presentation. Reserve investigation for signs pointing to an organic cause — a genuinely abrupt onset, an atypical age of onset, focal neurologic findings, or a temporal link to head injury, a new neurocognitive disorder, or a newly started dopaminergic/stimulant medication.
Treatment Targets
- Eliminate or substantially decrease obsessions and compulsions, aiming for full remission (Y-BOCS in or near the subclinical/mild range) rather than partial symptom reduction alone.
- Eliminate or reduce OCD-associated functional disability at work, school, and home, including reducing family/partner accommodation of rituals.
- Prevent relapse through an adequate duration of continued treatment.
- Restore overall quality of life.
- Identify and treat comorbid conditions (depression, another anxiety disorder, a related OCD-spectrum disorder) concurrently.
Choose Initial Treatment
First-line modality
1st line specialized cognitive behavioural therapy with exposure and response prevention (ERP) and pharmacotherapy with an SSRI are both first-line for OCD, with comparable efficacy evidence for each.[2][4] Specialized CBT/ERP is generally preferred as the true first choice where accessible, since relapse risk after stopping medication alone is high and CBT gains are more durable — but because access to a therapist with genuine OCD-specific ERP expertise is often limited, starting an SSRI while awaiting or arranging specialized CBT/ERP is a reasonable and common approach in practice.
SSRI selection
1st-line SSRI, any agent citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, or sertraline — no strong evidence favours one SSRI's efficacy over another for OCD, so selection is guided by tolerability, drug interactions, and prior response.[4]
Titration and trial duration — the single most important OCD-specific counselling point
Start at the lowest dose for about 1 week, then titrate to the maximum recommended or maximum tolerated dose. OCD requires notably higher target SSRI doses and a longer trial than depression or generalized anxiety before a trial can be called a failure — continue the maximum tolerated dose for a full 8-12 weeks (not the 4-6 weeks that is often adequate to judge a depression trial) before concluding the agent has failed.[2][5] If the patient reports feeling "improved" or "much improved" by 6 weeks, continue the same dose to complete the full 12-week trial rather than switching or escalating further. If there is no meaningful improvement by 6 weeks, first confirm adherence, then escalate to the maximum tolerated dose (including doses above the usual approved range where tolerated — see Special situation below) before concluding the trial has failed.[2]
Special situation — supratherapeutic SSRI dosing higher SSRI doses are often more effective, at the cost of poorer tolerability[6] — doses above the usual approved range (e.g., sertraline up to 400 mg/day) are sometimes used under specialist direction for genuine non-response at the standard maximum, with explicit informed patient consent. Before using a supratherapeutic dose, screen for risk factors for QTc prolongation/torsades de pointes (congenital long QT syndrome, heart failure, bradyarrhythmia, hypokalemia, hypomagnesemia); this caution applies with particular force to citalopram above 40 mg/day and escitalopram above 20 mg/day, where periodic ECG monitoring is advisable if the decision is made to proceed.[4]
After an inadequate response to the first adequate SSRI trial
Partial improvement at maximum tolerated dose augment with a low-dose second-generation antipsychotic (aripiprazole or risperidone) rather than switching to a second SRI monotherapy trial.[2][7]
No meaningful improvement despite an adequate 8-12 week trial at maximum tolerated dose switch to a different SSRI, or to clomipramine.[2]
If the second SRI trial also fails augment with aripiprazole or risperidone rather than attempting a third sequential SRI monotherapy trial.[2]
If antipsychotic augmentation is not tolerated or not effective a glutamate-modulating agent (lamotrigine or memantine as the better-tolerated options; topiramate or amantadine as further options) may be tried as an alternative or additional augmentation strategy.[2]
Combine with ERP whenever possible
Whenever accessible, add specialized CBT/ERP to pharmacotherapy — combination substantially improves response and reduces relapse susceptibility compared with medication alone, regardless of which medication track the patient is on.[2]
Non-Pharmacologic Treatment
Specialized CBT with exposure and response prevention (ERP)
ERP — systematic, graded exposure to feared stimuli while the patient refrains from performing the associated compulsion — is the active ingredient of first-line OCD psychotherapy. "Specialized" CBT for OCD is meaningfully different from generic anxiety-disorder CBT: it uses subtype-specific protocols tailored to the patient's particular obsession-compulsion pattern (contamination/washing, harm/checking, symmetry, taboo-thought themes), and produces substantial, durable symptom reduction for most patients who complete a course.[2] Many patients do not respond adequately to standard weekly in-office sessions alone and need increased session frequency/duration or therapist-assisted protocols delivered in the patient's own environment; centres offering subtype-specific, non-time-limited, therapist-assisted specialty protocols report the best outcomes. Where this level of expertise is not locally available, refer to or arrange consultation with a clinician with specific OCD/ERP expertise rather than substituting generic anxiety-focused CBT.
Internet-delivered CBT is a promising option for improving access where in-person specialized CBT is unavailable and merits continued study, but is not a substitute for specialized, therapist-directed ERP when that option is accessible.
Patients with prominent metacognitive dysfunction (strong symptom-related beliefs), overvalued ideas, or very high distress/intolerance of distress may not respond to ERP alone and can require additional specialized cognitive therapy techniques layered onto ERP.[2]
Family/partner accommodation
Identify and address family or partner participation in rituals (providing reassurance on demand, performing checking behaviours for the patient, altering household routines to avoid triggering obsessions) — accommodation is a common, correctable factor that maintains and can worsen OCD symptoms, and reducing it is a standard target woven into specialized CBT, particularly in pediatric treatment.[8]
OCD-related disorders have their own specialized protocols
Hoarding disorder and body dysmorphic disorder each have their own disorder-specific CBT protocols, distinct from standard OCD-focused ERP (see Special Populations).[2]
Not effective / reserved for refractory illness
Electroconvulsive therapy is not effective for OCD itself and is reserved for patients with a severe comorbid mood disorder. Brain stimulation (repetitive or deep transcranial magnetic stimulation) and, rarely, deep brain stimulation or neuroablative neurosurgery are reserved for patients who have not benefited from at least one full, adequately delivered trial of specialized CBT plus pharmacotherapy — see Treatment Failure & Next Steps.
Special Populations
Pregnancy
OCD symptoms, particularly harm-related obsessions about the baby, commonly worsen in pregnancy and can be extremely distressing; patients with these obsessions are not at higher risk of actually harming their child than the general population, but the distress and associated guilt/depression are real and often unvoiced unless directly asked about. Screen for OCD before conception where possible, and repeat screening during pregnancy and especially postpartum.[2] Specialized CBT/ERP can be delivered throughout pregnancy and is preferred first-line where accessible. If symptoms are severe and functionally impairing, SSRI pharmacotherapy is appropriate — apply the same general principles used for depression in pregnancy (see Depression's Special Populations for the shared pregnancy risk-benefit framework); paroxetine carries higher associated risk than other SSRIs and should generally be avoided as a new start in pregnancy.[2]
Breastfeeding
Nonpharmacologic treatment is preferred first-line in the postpartum period wherever possible. If drug therapy is needed, escitalopram and sertraline are preferred, given minimal transfer into breast milk.[2] A patient with severe postpartum OCD can become so distressed by harm-related obsessions that she refuses to care for or be alone with the infant — this needs urgent psychiatric consultation (see Red Flags & Refer), not reassurance alone.
Children and adolescents
SSRIs are first-line pharmacotherapy for pediatric OCD, generally combined with specialized CBT/ERP adapted for the child's developmental level and involving the family directly (including active work on reducing family accommodation of rituals).[8] Titrate more conservatively than in adults — modest dose increases roughly every 3 weeks rather than weekly — and monitor closely for behavioural activation (agitation, disinhibition, increased impulsivity), which is more common in younger children and can be a late-onset adverse effect that emerges as anxiety decreases; if activation is not manageable with a dose adjustment, rotate to a different SSRI rather than pushing through it.[8] All antidepressants carry the same boxed warning regarding increased suicidality risk under age 25 discussed in Red Flags & Refer, and this applies with particular relevance to pediatric OCD given how commonly it is treated in this age group. Continue an effective medication for 6-12 months after stabilization before considering a gradual taper.[8] Fluvoxamine, fluoxetine, and sertraline have the most robust pediatric OCD evidence base; use adult titration principles adapted to lower starting doses and slower increases, with specialist input for dosing outside these three agents.
Older adults
Start SSRIs at a lower dose with slower titration than in a younger adult. Apply the citalopram/escitalopram QTc-prolongation caution with particular care in this age group, given a higher baseline prevalence of cardiac risk factors and polypharmacy. Clomipramine's anticholinergic and cardiovascular burden makes it a poor choice in most older patients — favour an SSRI or, for augmentation, aripiprazole/risperidone with close monitoring for orthostatic hypotension and falls risk.
Renal and hepatic impairment
Dose reduction may be needed for hepatically metabolized agents (most SSRIs, clomipramine) in significant hepatic impairment — start low and titrate slowly. No specific renal dose adjustment is required for most SSRIs at usual doses, but use caution with any agent in significant renal impairment given reduced overall clearance reserve; memantine's clearance can theoretically be reduced by urinary alkalizers (e.g., carbonic anhydrase inhibitors).
OCD-related disorders
Both are DSM-5-TR obsessive-compulsive and related disorders, treated with serotonergic medication as in OCD, but with real treatment differences worth knowing.
Hoarding disorder
Persistent difficulty discarding possessions regardless of actual value, driven by a perceived need to save items and distress at the thought of discarding them, resulting in clutter that compromises the intended use of living spaces. Hoarding disorder responds less robustly to SSRIs than classic OCD and needs a hoarding-specific CBT protocol (distinct from standard OCD-focused ERP) as a central part of treatment, not an adjunct — insight is often poor, and motivation-building work is typically needed before exposure-based strategies can proceed.[9] When hoarding is severe enough to pose a genuine safety hazard (fire, structural, sanitation, fall risk), this is itself a red flag requiring a coordinated response — see Red Flags & Refer.
Body dysmorphic disorder (BDD)
Preoccupation with 1 or more perceived defects in physical appearance that are not observable or appear only slight to others, accompanied by repetitive behaviours (mirror-checking, excessive grooming, skin-picking, reassurance-seeking) or mental acts (comparing one's appearance with others') in response to the preoccupation. SSRIs are first-line pharmacotherapy, generally requiring doses at or above the maximum used for OCD and a similarly long trial (12 weeks) before declaring failure — a genuinely full-dose, full-duration trial matters even more in BDD, since many patients presenting for pharmacotherapy have previously only received an inadequate trial.[10] BDD carries a real and often underrecognized suicide risk, which lowers the threshold for starting pharmacotherapy promptly rather than trialling psychotherapy alone first in more severely affected patients. Refractory cases may benefit from augmentation with a dopamine antagonist (including haloperidol in more severe or delusional-level presentations).[10] CBT for BDD uses its own disorder-specific protocol addressing appearance-related beliefs and behaviours, distinct from standard OCD ERP.
Monitoring & Follow-Up
Track response with the Y-BOCS (or a brief validated alternative such as the 6-item Brief Obsessive Compulsive Scale) at the 4-week, 12-week, and other key clinical decision points rather than relying on unstructured impression alone.[2] Reassess specifically at week 4: minimal improvement at this point makes a strong full response by 12 weeks substantially less likely, but does not by itself justify stopping early — continue the planned full-duration trial at the maximum tolerated dose unless adverse effects require a change, since meaningful further gains commonly continue to accrue between weeks 6 and 12.[11][2] If augmentation is added, reassess its specific contribution at 4 weeks.
If treatment is successful, continue for at least 1 year before considering any dose reduction — relapse rates after early discontinuation are high, and this applies to medication monotherapy in particular.[2] Wait for a period of sustained psychosocial stability before attempting discontinuation, individualize the decision to continue long-term therapy, and taper any antidepressant gradually rather than stopping abruptly, warning the patient to report early signs of relapse during the taper. After a course of specialized CBT/ERP, some patients can maintain stability after a carefully monitored SRI taper — this is a reasonable goal to discuss once ERP has been completed, not a default assumption for every patient.[2]
At every follow-up, monitor for ongoing suicidal ideation (especially in patients under 25 and at any dose change), adherence, and — specifically for the antipsychotic augmentation agents — weight, metabolic parameters, and extrapyramidal symptoms. A community pharmacist is well positioned to catch the two most common, entirely preventable causes of apparent treatment failure: a patient who never reached an adequate dose, and a patient who stopped a trial well before the 8-12 week mark because early benefit felt underwhelming.
Common Errors to Avoid
- Declaring an SSRI trial a failure before 8-12 weeks at the maximum tolerated dose — the single most common, entirely avoidable cause of apparent "SSRI failure" in OCD is a trial that was simply never adequate in dose or duration, not a genuine non-response.[12]
- Using the depression trial-duration rule (4-6 weeks) for OCD instead of the correct, longer 8-12 week rule.
- Stopping dose escalation at the standard depression/anxiety target dose instead of continuing to the OCD-specific maximum tolerated dose.
- Switching to a new SRI after only a partial response instead of augmenting — and, conversely, augmenting after a genuine zero response instead of switching first.
- Attempting a third sequential SRI monotherapy trial instead of moving to antipsychotic augmentation after 2 adequate SRI trials have failed.
- Recommending low-intensity self-help CBT or a stepped-care approach as a substitute for specialized, subtype-specific CBT/ERP — this is not evidence-based for OCD and risks avoidable undertreatment.
- Treating medication and ERP as competing options rather than combining them whenever possible — combination meaningfully outperforms either alone.
- Using benzodiazepines or lithium as OCD monotherapy — neither is effective for core OCD symptoms; reserve them for a specific comorbid indication (e.g., severe comorbid anxiety or a mood disorder).
- Missing a reversible medication or substance trigger (a new stimulant, dopamine agonist, or serotonin-dopamine antagonist) in a patient with new-onset obsessive-compulsive symptoms.
- Treating body dysmorphic disorder at standard depression-range SSRI doses instead of the higher, OCD-range doses it actually requires.
- Missing severe hoarding as a home-safety issue because it was framed only as a psychiatric symptom rather than also flagged for practical safety triage.
- Not screening explicitly for suicidal ideation at SSRI initiation and at every dose change, particularly in patients under 25.
- Stopping an SSRI or clomipramine abruptly instead of tapering gradually.
Clinical Decision Algorithm
Drug Tables
How to use this table: Doses are adult doses and require patient-specific confirmation, including renal/hepatic adjustment — see Special Populations for pediatric, pregnancy/breastfeeding, and older-adult dosing considerations. Select any drug name to open its complete Pharmasist Drug Database page.
Selective serotonin reuptake inhibitors (SSRIs) — 1st line
All 6 agents are considered comparably effective for OCD; selection is guided by tolerability and interaction profile, not superior efficacy of one over another. OCD requires notably higher target doses and a longer (8-12 week) trial at the maximum tolerated dose than depression or generalized anxiety before a trial can be judged to have failed.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Citalopram | Initial: 10-20 mg PO daily Usual: 20-40 mg PO daily Off-label/specialist: Above 40 mg/day with QTc precautions | GI upset, dry mouth, diaphoresis, headache, dizziness, insomnia, sexual dysfunction, weight gain, rare SIADH with hyponatremia; dose-related QTc prolongation | Concurrent use with MAOIs, linezolid, or methylene blue is contraindicated (serotonin syndrome risk); use caution combining with other serotonergic agents. Increased GI bleeding risk with NSAIDs/antiplatelet agents. Avoid combining with other QTc-prolonging drugs. | Off-label dosing above 40 mg/day requires screening for QTc risk factors and periodic ECG monitoring if used. |
| Escitalopram | Initial: 5-10 mg PO daily Usual: 10-20 mg PO daily Off-label/specialist: Above 20 mg/day with QTc precautions | Same profile as citalopram; dose-related QTc prolongation | Concurrent use with MAOIs, linezolid, or methylene blue is contraindicated (serotonin syndrome risk); use caution combining with other serotonergic agents. Increased GI bleeding risk with NSAIDs/antiplatelet agents. Avoid combining with other QTc-prolonging drugs. | Off-label dosing above 20 mg/day requires screening for QTc risk factors and periodic ECG monitoring if used. |
| Fluoxetine | Initial: 10-20 mg PO daily Usual: 40-80 mg PO daily Maximum: 80 mg/day | GI upset, insomnia, anxiety/activation on initiation, sexual dysfunction, weight gain | Concurrent use with MAOIs, linezolid, or methylene blue is contraindicated (serotonin syndrome risk); use caution combining with other serotonergic agents. Increased GI bleeding risk with NSAIDs/antiplatelet agents. Avoid combining with other QTc-prolonging drugs. Potent CYP2D6 inhibitor. | Longer half-life (4-6 days) than other SSRIs allows a more rapid taper; needs a longer washout before starting an MAOI. |
| Fluvoxamine | Initial: 50-100 mg PO daily Usual: 200-300 mg PO daily Maximum: 300 mg/day | GI upset (prominent), somnolence, headache, sexual dysfunction, weight gain | Concurrent use with MAOIs, linezolid, or methylene blue is contraindicated (serotonin syndrome risk); use caution combining with other serotonergic agents. Increased GI bleeding risk with NSAIDs/antiplatelet agents. Avoid combining with other QTc-prolonging drugs. Potent CYP1A2 inhibitor. | Review CYP1A2-dependent medications (theophylline, clozapine, tizanidine) before starting. |
| Paroxetine | Initial (immediate-release): 10-20 mg PO daily Usual (immediate-release): 40-60 mg PO daily Maximum (immediate-release): 60 mg/day Controlled-release: 25-50 mg PO daily | GI upset, anticholinergic effects (dry mouth, constipation), somnolence, sexual dysfunction, weight gain, discontinuation symptoms | Concurrent use with MAOIs, linezolid, or methylene blue is contraindicated (serotonin syndrome risk); use caution combining with other serotonergic agents. Increased GI bleeding risk with NSAIDs/antiplatelet agents. Avoid combining with other QTc-prolonging drugs. Potent CYP2D6 inhibitor. | Shortest SSRI half-life — highest discontinuation-symptom risk with abrupt stop. Avoid starting in pregnancy. |
| Sertraline | Initial: 50-100 mg PO daily Usual: 200 mg PO daily Supratherapeutic/specialist: Up to 400 mg/day | GI upset, insomnia, sexual dysfunction, weight gain | Concurrent use with MAOIs, linezolid, or methylene blue is contraindicated (serotonin syndrome risk); use caution combining with other serotonergic agents. Increased GI bleeding risk with NSAIDs/antiplatelet agents. Avoid combining with other QTc-prolonging drugs. Weak CYP2D6 inhibitor. | Preferred SSRI in pregnancy/breastfeeding. Supratherapeutic dosing up to 400 mg/day used under specialist direction with informed consent for confirmed non-response at 200 mg/day. |
Tricyclic antidepressant — 2nd-line monotherapy
Clomipramine is similarly effective to SSRIs in head-to-head evidence, but its adverse-effect burden and overdose lethality make it a reserved, not first, choice.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Clomipramine | Initial: 25 mg PO daily, increase Q3-5 days as tolerated Usual: 100-200 mg PO daily Maximum: 250 mg/day | Anticholinergic effects (dry mouth, blurred vision, constipation), sedation, weight gain, nausea, orthostatic hypotension, tachycardia/arrhythmias, anorgasmia/erectile dysfunction; CNS effects (agitation, confusion) on initiation | Increases effect of anticholinergic drugs and CNS depressants; increases warfarin effect; do not use with MAOIs concurrently; increases risk of seizures at higher doses | Screen for cardiac risk factors and baseline ECG in patients over 40 or with cardiac history before starting. Dangerous in overdose — use particular caution with active suicidal ideation. Generally avoided in cross-taper switches; use a defined washout instead. |
SNRI and NaSSA — 2nd-line monotherapy
Reasonable options after SSRI failure or intolerance, though generally regarded as somewhat less preferred than a genuine switch to a second SSRI.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Venlafaxine XR | Initial: 37.5-75 mg PO daily Usual: 112.5-225 mg PO daily Maximum: 300 mg/day | Nausea, sleep disturbance, dizziness, dry mouth, dose-related hypertension (especially ≥225 mg/day) | Use with MAOIs can cause a potentially fatal reaction (tremor, agitation, hyperthermia, hypertension); CYP2D6/CYP3A4 inhibitors increase levels | Believed to act via serotonin and norepinephrine reuptake inhibition; some evidence suggests switching SSRI-to-SSRI may outperform switching to venlafaxine after SSRI failure. |
| Mirtazapine | Initial: 30 mg PO at bedtime Usual: 30-60 mg PO at bedtime | Somnolence, increased appetite/weight gain, dizziness | Do not use with MAOIs; additive sedation with other CNS depressants; substrate of CYP1A2/2D6/3A4 | Weak monotherapy evidence — reasonable specifically when a patient cannot tolerate an SSRI, or as an augmentation option. |
Dopamine receptor antagonist/partial agonist augmentation — 1st-line augmentation for partial SSRI response
Titrate to the middle of the standard antipsychotic dosing range — higher than typical augmentation doses used in major depressive disorder. Reassess efficacy specifically at 4 weeks; weigh metabolic and movement-disorder adverse effects against benefit at every review, and do not continue indefinitely without reassessment.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Aripiprazole | Initial and usual: 10-15 mg PO daily | Akathisia, parkinsonism, dizziness, headache, GI upset, insomnia, somnolence, weight gain, lipid/glucose dysregulation | Strong CYP2D6/3A4 inducers (carbamazepine, rifampin, phenytoin) significantly decrease levels; strong CYP2D6/3A4 inhibitors (ketoconazole, quinidine, fluoxetine, paroxetine) significantly increase levels | Advise on antipsychotic-associated body-temperature dysregulation — hydration and sun protection. |
| Risperidone | Initial: 0.5 mg PO daily Titration: Increase by 0.5-1 mg every 3-7 days as tolerated Usual maximum: 3 mg/day | Somnolence, headache, weight gain, lipid/glucose dysregulation, orthostatic hypotension, rhinitis, dose-related hyperprolactinemia, EPS, QTc prolongation | CYP3A4 inhibitors (clarithromycin, erythromycin, grapefruit juice, ketoconazole, prednisone) increase levels; CYP3A4 inducers (carbamazepine, phenytoin, rifampin) decrease levels; may potentiate antihypertensive effect | Advise on antipsychotic-associated body-temperature dysregulation. Risk of intraoperative floppy iris syndrome in patients with prior exposure undergoing cataract surgery — flag this in the chart. |
Glutamate-modulating agents — 2nd/3rd-line augmentation after antipsychotic augmentation fails or is not tolerated
Preliminary evidence supports these agents added to an SSRI in refractory OCD. Lamotrigine and memantine are generally the best-tolerated of the group and are reasonable next options; topiramate has poorer tolerability but is a reasonable choice with comorbid migraine, binge-eating pattern, or antipsychotic-associated weight gain.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Lamotrigine | Weeks 1-2: 25 mg PO at bedtime Weeks 3-4: 50 mg PO at bedtime Week 5: 100 mg PO at bedtime Week 6 onward: 200 mg PO at bedtime | Benign rash (stop immediately if it occurs — risk of Stevens-Johnson syndrome), dizziness, drowsiness | Hormonal contraceptives may reduce lamotrigine levels by up to half; valproic acid increases lamotrigine levels (requires a slower titration schedule); carbamazepine/phenytoin decrease lamotrigine levels and lamotrigine may increase carbamazepine toxicity | The stepped titration schedule below is mandatory for rash-risk mitigation — never shortcut it. |
| Memantine | Initial: 10 mg PO daily x 1 week Usual: 20 mg/day in 1-2 divided doses | Generally well tolerated; dizziness, headache, confusion, constipation, nausea/vomiting | Not metabolized via cytochrome P450; urinary alkalizers (e.g., carbonic anhydrase inhibitors) may theoretically reduce clearance | Favourable interaction profile relative to the antipsychotic augmentation agents. |
| Topiramate | Initial: 25 mg PO daily Titration: Increase by 25 mg every 1-2 weeks Usual range: 50-200 mg/day | Dizziness, ataxia, tremor, sedation, cognitive impairment, GI upset, weight loss, metabolic acidosis, nephrolithiasis, rare acute myopia/angle-closure glaucoma | CYP2C19 inhibitors (SSRIs, isoniazid, omeprazole, moclobemide) increase topiramate levels; phenytoin/carbamazepine decrease topiramate levels; reduces oral contraceptive effectiveness — add barrier contraception | Warn patients to seek emergency assessment immediately for acute eye pain, redness, or vision change (possible angle-closure glaucoma, resolves with discontinuation). Counsel on CNS-depressant effects relevant to driving. |
| Amantadine | Usual: 100 mg PO daily | Nausea, constipation, dry mouth, insomnia, anxiety, impaired concentration, livedo reticularis, orthostatic hypotension, ankle edema | Not metabolized via cytochrome P450 | Taper gradually — abrupt discontinuation carries a risk of a parkinsonism-hyperpyrexia-like syndrome. |
References
- Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) — American Psychiatric Association. American Psychiatric Publishing, 2022
- Canadian clinical practice guidelines for the management of anxiety, posttraumatic stress and obsessive-compulsive disorders — BMC Psychiatry, Canadian Anxiety Guidelines Initiative Group (Katzman MA, Bleau P, Blier P, Chokka P, Kjernisted K, Van Ameringen M, et al.). BMC Psychiatry 2014;14(Suppl 1):S1
- The Yale-Brown Obsessive Compulsive Scale. I. Development, use, and reliability — Archives of General Psychiatry (Goodman WK, Price LH, Rasmussen SA, et al.). Arch Gen Psychiatry 1989;46(11):1006-1011
- World Federation of Societies of Biological Psychiatry (WFSBP) guidelines for treatment of anxiety, obsessive-compulsive and posttraumatic stress disorders – Version 3, Part II: OCD and PTSD — World Journal of Biological Psychiatry (Bandelow B, Alaee A, Ansseau M, et al.). World J Biol Psychiatry 2023;24(2):118-134
- Specialty knowledge and competency standards for pharmacotherapy for adult obsessive-compulsive disorder — Psychiatry Research (Pittenger C, Brennan BP, Koran L, et al.). Psychiatry Res 2021;300:113853
- Meta-analysis of the dose-response relationship of SSRI in obsessive-compulsive disorder — Molecular Psychiatry (Bloch MH, McGuire J, Landeros-Weisenberger A, et al.). Mol Psychiatry 2010;15(8):850-855
- Cognitive behavioral therapy vs risperidone for augmenting serotonin reuptake inhibitors in obsessive compulsive disorder — JAMA Psychiatry (Simpson HB, Foa EB, Liebowitz MR, et al.). JAMA Psychiatry 2013;70(11):1190-1199
- Practice parameter for the assessment and treatment of children and adolescents with obsessive-compulsive disorder — Journal of the American Academy of Child & Adolescent Psychiatry (Geller DA, March J; AACAP Committee on Quality Issues). J Am Acad Child Adolesc Psychiatry 2012;51(1):98-113
- Cognitive behavioral therapy for hoarding disorder: a meta-analysis — Depression and Anxiety (Tolin DF, Frost RO, Steketee G, Muroff J). Depress Anxiety 2015;32(3):158-166
- Pharmacotherapy and psychotherapy for body dysmorphic disorder — Cochrane Database of Systematic Reviews (Ipser JC, Sander C, Stein DJ). Cochrane Database Syst Rev 2009;(1):CD005332
- Can early improvement be an indicator of treatment response in obsessive-compulsive disorder? Implications for early-treatment decision-making — Journal of Psychiatric Research (da Conceicao Costa DL, Shavitt RG, Castro Cesar RC, et al.). J Psychiatr Res 2013;47(11):1700-1707
- Evidence-based pharmacotherapy of obsessive-compulsive disorder — International Journal of Neuropsychopharmacology (Fineberg NA, Brown A, Reghunandanan S, Pampaloni I). Int J Neuropsychopharmacol 2012;15(8):1173-1191
- Atypical antipsychotic augmentation in SSRI treatment refractory obsessive-compulsive disorder: a systematic review and meta-analysis — BMC Psychiatry (Veale D, Miles S, Smallcombe N, et al.). BMC Psychiatry 2014;14(1):317
Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.