Pruritus

Clinical Snapshot

Pruritus is the sensation of itch, and like pain, it is a symptom that can arise from many different underlying processes rather than a single disease. Acute, localized itch (an insect bite, a brief contact reaction) rarely needs formal work-up. Chronic pruritus -- itch lasting six weeks or longer -- is different: it can be driven by a primary skin disease, but it is also a recognized presenting feature of systemic disease (renal, hepatic, hematologic, endocrine, or malignant), of a medication, of a neuropathic process, or of a psychiatric condition, and in a subset of patients no cause is ever identified despite a thorough work-up.^[1] The management principle that follows from this is simple to state and easy to skip in practice: identify and treat the underlying cause whenever one exists, and reserve purely symptomatic antipruritic therapy -- matched to the itch's likely mechanism, not applied reflexively -- for itch that persists despite this, or for which no treatable cause is found.

Recognize the Condition

What to look for on skin examination

The single most important branch point on examination is whether there is a primary skin lesion that explains the itch, or only secondary changes caused by scratching. Primary dermatologic disease (eczema, psoriasis, scabies, urticaria, a drug eruption) has its own characteristic morphology and is addressed as that specific diagnosis. When the skin shows only excoriations, lichenification (thickened, leathery skin from chronic rubbing), prurigo nodules, or is entirely normal, the itch itself is the primary problem and the visible skin changes are secondary to scratching -- this pattern should prompt a search for a systemic, neuropathic, psychogenic, or drug-related cause rather than a dermatologic diagnosis. Excoriation and lichenification are easy to misread as a primary inflammatory skin condition when they are actually the downstream result of chronic pruritus from an entirely different cause.

Categories of chronic pruritus

Dermatologic

Caused by a primary inflammatory or infectious skin disease -- atopic dermatitis, psoriasis, scabies, urticaria, xerosis/dry skin, contact dermatitis. Skin examination reveals the primary lesion; treat that specific diagnosis.

Systemic

Caused by an underlying non-dermatologic disease -- renal (uremic), hepatic/cholestatic, hematologic (including malignancy), endocrine, or infectious. Skin is normal apart from scratch-related secondary changes; see the differential table in Assessment & Diagnosis.

Neurological/neuropathic

Arises from damage or dysfunction of afferent itch pathways -- peripheral nerve, nerve root, or central nervous system. Classic examples include notalgia paresthetica, brachioradial pruritus, post-herpetic itch, and itch following nerve injury or stroke; typically localized to a specific dermatome or nerve territory.

Psychogenic/psychosomatic

Attributed to, or substantially amplified by, an underlying psychiatric condition (depression, anxiety, obsessive-compulsive disorder, delusional infestation) once organic causes have been reasonably excluded.

Mixed

Two or more of the above coexist and each contributes -- for example, xerosis layered on top of uremic pruritus in a patient with chronic kidney disease.

Pruritus of unknown origin

Chronic pruritus that remains unexplained despite a thorough, guideline-directed work-up. A diagnosis of exclusion, never a default first assumption.

^[1]

Risk Factors

Older age -- both because xerosis (dry skin) becomes more common and because the prevalence of chronic kidney disease, malignancy, and polypharmacy all rise with age.
Known chronic kidney disease, particularly hemodialysis-dependent end-stage renal disease.
Known cholestatic or other chronic liver disease.
Hematologic conditions -- iron deficiency, polycythemia vera, lymphoma (particularly Hodgkin lymphoma), and other myeloproliferative or lymphoproliferative disorders.
Thyroid dysfunction, either hyperthyroidism or hypothyroidism.
HIV infection.
New or recently changed medication, especially an opioid, or any of the drug classes listed in Common Errors to Avoid.
Personal or family history of atopic disease.
Underlying psychiatric illness, particularly depression, anxiety, or a somatoform pattern.
Xerosis from any cause, including low ambient humidity, frequent hot showers/baths, and harsh or fragranced cleansing products.
Pregnancy -- a distinct set of pregnancy-specific pruritic conditions exists and needs its own targeted evaluation; see Special Populations.

Red Flags & Refer

Pruritus without an obvious dermatologic or drug-related explanation can be the presenting feature of significant systemic disease. Escalate promptly for any of the following:

Unintentional weight loss, fevers or chills, drenching night sweats, or palpable lymphadenopathy -- these warrant urgent work-up for lymphoma or another malignancy rather than continued symptomatic itch treatment.
Jaundice, scleral icterus, dark urine, or pale stool -- suggests cholestatic liver disease and needs prompt hepatic assessment.
Signs or a known history of significant renal impairment (edema, uremic symptoms, established advanced chronic kidney disease) -- confirm the itch is being appropriately attributed and managed within the patient's renal care.
Hepatosplenomegaly on examination.
Pallor, fatigue, or other features suggesting anemia or a hematologic disorder.
New pruritus, particularly of the palms and soles and worse at night, in a pregnant patient -- raises concern for intrahepatic cholestasis of pregnancy, which carries fetal risk and needs prompt obstetric assessment; this is outside the scope of routine symptomatic itch management.
Extensive skin involvement, erosions, blistering, or a marked adverse impact on quality of life or sleep -- refer to dermatology.
Generalized pruritus persisting despite an adequate trial of general skin care and appropriate first-line therapy, with no cause identified on initial work-up -- refer for further systemic investigation rather than repeatedly escalating symptomatic treatment alone.

Assessment & Diagnosis

Differential diagnosis of systemic causes

This is the core of the pharmacist-relevant work-up once a primary skin disease has been reasonably excluded on examination.

Category	Representative causes	Clues on history/exam	Initial test(s)
Renal	Chronic kidney disease, particularly hemodialysis-dependent	Known CKD/end-stage renal disease; generalized itch, often worse around or after dialysis sessions	Serum creatinine/eGFR
Hepatic/cholestatic	Primary biliary cholangitis, primary sclerosing cholangitis, other cholestatic liver disease, biliary obstruction	Jaundice, dark urine, pale stool, right-upper-quadrant discomfort; itch classically affects palms/soles and worsens at night	Liver function tests including bilirubin; consider hepatobiliary imaging
Hematologic	Iron deficiency anemia, polycythemia vera, lymphoma (especially Hodgkin), other myelo-/lymphoproliferative disease	Aquagenic itch pattern (onset after a hot bath/shower) suggests polycythemia vera; pallor/fatigue suggests iron deficiency; weight loss/night sweats/lymphadenopathy suggests lymphoma	CBC with differential, ferritin; further testing directed by findings
Endocrine	Hypothyroidism, hyperthyroidism	Cold/heat intolerance, weight change, other thyroid symptoms	TSH
Infectious	HIV	Relevant risk factors, other systemic symptoms	HIV serology
Drug-induced	Opioids, ACE inhibitors/ARBs, beta-blockers, calcium channel blockers, hydrochlorothiazide, amiodarone, statins, antimalarials, allopurinol, penicillins, macrolides, trimethoprim/sulfamethoxazole, immune checkpoint inhibitors and other targeted cancer therapies, stimulants	Temporal relationship to a new or changed medication; itch can occur without any rash	Medication review; a supervised trial of stopping the suspected drug (at least 6 weeks) where feasible
Psychogenic/psychiatric	Depression, anxiety, delusional infestation, obsessive-compulsive spectrum conditions	Psychiatric comorbidity, clear correlation with stress, no organic cause found despite reasonable work-up	Clinical assessment; psychiatric referral when suspected
Neuropathic	Notalgia paresthetica, brachioradial pruritus, post-herpetic itch, nerve compression or injury	Localized distribution corresponding to a dermatome or specific nerve territory	Clinical; imaging only if a structural cause is suspected
Unknown origin	Diagnosis of exclusion	No cause identified despite a thorough, directed work-up	None further indicated once work-up above is complete and negative

History

Onset, duration, distribution (localized vs. generalized), and any temporal pattern (constant, worse at night, worse after bathing).
Full skin-care routine -- cleansing products, topical products applied, frequency and temperature of showers/baths, use of hot tubs.
Complete prescription, nonprescription, and recreational/illicit drug history, including anything started or changed in the weeks before the itch began.
Directed systemic-symptom review: unintentional weight loss, fevers, night sweats, fatigue, cold/heat intolerance, change in urine or stool colour.
Relevant travel or immigration history, given that some parasitic causes of itch are geographically restricted.
Psychosocial stressors, mood, anxiety, and sleep quality -- both as possible contributors and as consequences of chronic itch.

Physical examination

Full skin examination for a primary rash or lesion versus only secondary changes (excoriation, lichenification, prurigo nodules) or normal-appearing skin.
Test for dermatographism (stroke the skin firmly and look for a raised wheal a few minutes later) -- a positive test identifies a histamine-mediated itch mechanism that typically responds to antihistamines.
Look specifically for burrows to evaluate for scabies.
Assess for jaundice or abnormal pigmentation, lymphadenopathy, and hepatosplenomegaly.

When laboratory testing is, and is not, indicated

Laboratory work-up is appropriate once a primary dermatologic cause has been reasonably excluded, not as a routine reflex in every patient with itch -- a patient with a clear primary dermatosis should be treated for that diagnosis rather than sent for a broad systemic panel. When systemic work-up is indicated: CBC with differential, fasting glucose, liver function tests including bilirubin, renal function tests, chest x-ray, and HIV testing form the reasonable initial panel; TSH, calcium, serum protein electrophoresis, ferritin, and stool for ova and parasites (with a relevant travel history) can be added if this initial work-up is unrevealing and itch persists.^[1]

Treatment Targets

Identify and treat, or refer for treatment of, any underlying dermatologic, systemic, or drug-related cause -- this takes priority over purely symptomatic antipruritic therapy whenever a cause exists.
Reduce itch intensity and frequency to a level the patient finds tolerable, recognizing that complete elimination is not always achievable, particularly for pruritus of unknown origin.
Break the scratch-itch cycle to prevent secondary skin damage -- excoriation, lichenification, prurigo nodularis, and secondary skin infection.
Restore sleep quality, since itch is frequently worse at night and poor sleep in turn lowers the itch threshold.
Select the antipruritic option matched to the itch's likely mechanism rather than defaulting to the same agent for every patient, since efficacy differs substantially by cause.
Minimize treatment-related harm -- avoid prolonged topical corticosteroid use where there is no inflammatory component, and avoid escalating to a systemic agent with real toxicity before simpler, safer measures have had an adequate trial.

Choose Initial Treatment

Direct treatment rule

Every patient, regardless of cause should be started on general skin-care measures (see Non-Pharmacologic Treatment) as foundational therapy -- these are not optional adjuncts, they measurably reduce itch on their own and make every other treatment work better.

When an identifiable underlying dermatologic, systemic, or drug-related cause is found, treat that cause directly -- topical and systemic antipruritics are adjunctive symptom control while the underlying problem is addressed, not a substitute for addressing it.

Itch with a visible inflammatory skin component (redness, and often tenderness, at the itchy site) responds to a topical corticosteroid matched to site and severity, or a topical calcineurin inhibitor for sensitive sites (face, skin folds, genitals) where a corticosteroid should be minimized.

Do not use a topical corticosteroid for itch without visible inflammation -- it will not help pruritus that is not due to skin inflammation, and it exposes the patient to atrophy and other local corticosteroid adverse effects for no benefit.

Mild, localized itch without inflammation responds reasonably to a topical antipruritic (menthol/camphor lotion, or topical capsaicin for a genuinely localized neuropathic pattern such as notalgia paresthetica).

Nonsedating oral antihistamines are only reliably effective for histamine-mediated itch -- urticaria, dermatographism, mastocytosis. For most other causes of chronic pruritus the evidence for benefit is weak, and a nonsedating antihistamine should not be relied on as first-line therapy outside these histamine-mediated presentations.^[1]

Generalized or moderate-to-severe itch persisting despite topical measures and treatment of any identified cause should move to a systemic agent selected by the itch's likely mechanism: a gabapentinoid for neuropathic or uremic itch, a bile acid sequestrant (then rifampin, then naltrexone if refractory) for cholestatic itch, an updosed nonsedating antihistamine for histamine-mediated itch, and mirtazapine or a sedating antihistamine at bedtime for nocturnal or refractory itch -- see Pharmacologic Treatment Options and the Systemic Therapy Selection algorithm.

Non-Pharmacologic Treatment

Hydrate the skin. Dry skin (xerosis) from low ambient humidity, hot showers, or harsh soap frequently worsens itch of any cause. Use a fragrance-free, pH-neutral synthetic detergent cleanser rather than traditional alkaline soap, take lukewarm (not hot) showers or baths limited to 5-10 minutes, and use an indoor humidifier in dry conditions.
Apply moisturizer immediately after bathing, while the skin is still slightly damp, to trap hydration. Ointment-based moisturizers are more occlusive and effective for very dry skin; creams are lighter and often better tolerated for daily use over larger areas.
Minimize friction and irritation. Pat the skin dry rather than rubbing; apply topical products by dabbing. Choose soft, loose-fitting cotton clothing and avoid wool or rough synthetic fabrics. Rinse laundry detergent thoroughly and use fragrance-free laundry and personal-care products.
Avoid known aggravating factors -- prolonged hot showers/baths, hot tubs and saunas, spicy foods, caffeine, alcohol, and excessive heat/humidity. A brief symptom diary can help an individual patient identify their own specific triggers.
Break the scratch-itch cycle. Scratching provides brief relief but perpetuates and worsens itch, and causes the secondary skin damage (excoriation, lichenification, infection risk) that then itches on its own. Keep fingernails and toenails short and smooth; a light covering of clothing over an itchy area reduces unintentional scratching; cool compresses applied for about 20 minutes, several times daily, help acute localized flares.
Address nighttime itch specifically, since pruritus is frequently worse at night. Apply moisturizer or a topical antipruritic just before bed, use lightweight bedclothes, keep the bedroom cool, and consider a sedating antihistamine at bedtime when sedation itself (not a true antipruritic effect) is the goal -- see Pharmacologic Treatment Options.
Colloidal oatmeal bath preparations can be soothing as an adjunct for generalized itch.
For patients with a substantial psychological or stress component, structured approaches such as habit-reversal training, relaxation techniques, and education on the itch-scratch cycle can meaningfully help, though access to these programs is often limited.

Pharmacologic Treatment Options

Drug / intervention	Role	Dose / use	Important adverse effects	Teaching points
Triamcinolone acetonide 0.1% cream Preferred	Topical corticosteroid for itch with a visible inflammatory component	Apply thin film 1-2 times daily; limit continuous use to 2-3 weeks on thin-skinned sites	Local burning, atrophy/striae with prolonged use, especially on the face or skin folds	Only indicated when the skin is genuinely inflamed. Not for itch without redness.
Pimecrolimus 1% cream Preferred	Non-steroidal option for inflammatory itch on sensitive sites (face, folds, genitals)	Apply twice daily to affected area	Transient burning/stinging at application site, usually improves within days	Avoid excess alcohol intake, which can cause transient facial flushing/burning at the site.
Camphor/menthol topical lotion Preferred	Mild, non-inflammatory, or localized itch of any cause	Apply to affected area(s) up to 3-4 times daily as needed	Local burning/stinging sensation on application (expected), rare contact dermatitis	Cooling effect reduces the sensation of itch. Avoid in children under 2 years and on broken skin.
Capsaicin cream Special situation	Localized neuropathic itch (notalgia paresthetica, brachioradial pruritus) or uremic itch	Apply to affected area at least 3-4 times daily	Marked burning/stinging on initial application, improves with continued regular use	Must be used consistently to work -- initial burning causes many patients to stop before benefit appears.
Cetirizine Preferred	Histamine-mediated itch: urticaria, dermatographism, mastocytosis	10 mg PO once daily; can be updosed up to 4-fold per current urticaria guidance if inadequate response	Mild sedation at standard dose, more at updosed regimens	Limited efficacy for chronic itch that is not histamine-mediated -- do not rely on this class outside urticarial presentations.
Hydroxyzine Alternative	Nocturnal itch of any cause, via sedation rather than a specific antipruritic effect	25-50 mg PO at bedtime	Marked sedation, anticholinergic effects, caution in older adults	Helps sleep despite ongoing itch; it is the sedation, not H1 blockade of the itch mechanism, doing the work for most non-histaminergic causes.
Gabapentin Preferred	Neuropathic or uremic itch	Uremic pruritus: 100 mg PO after each hemodialysis session, titrate cautiously. Other neuropathic itch: start 300 mg PO at bedtime, titrate to 900-1800 mg/day divided	Sedation, dizziness, peripheral edema; renal dose adjustment required	Genuine efficacy evidence for neuropathic and uremic itch, unlike antihistamines for these causes.
Cholestyramine Preferred	Cholestatic/hepatic itch, 1st-line systemic agent	Start 4 g PO once or twice daily, titrate as tolerated to a usual maximum of 16 g/day divided	GI upset, constipation, interferes with absorption of other oral drugs and fat-soluble vitamins	Separate from other oral medications by at least 2-4 hours.
Rifampin Special situation	Cholestatic itch refractory to a bile acid sequestrant	150-300 mg PO twice daily, with slow up-titration and baseline/periodic liver enzyme monitoring	Hepatotoxicity, orange discolouration of body fluids, numerous CYP450 drug interactions	Restrict to patients with normal baseline AST/ALT and monitor closely given hepatotoxicity risk.
Naltrexone Special situation	Cholestatic itch refractory to a bile acid sequestrant and rifampin	Start 12.5 mg PO daily, titrate gradually to a usual target of 50 mg PO daily	Opioid-withdrawal-like reaction on initiation, hepatotoxicity (monitor LFTs)	Contraindicated in patients taking opioid analgesics -- will precipitate withdrawal.
Mirtazapine Special situation	Nocturnal, paraneoplastic, or otherwise refractory itch	15 mg PO at bedtime, may increase to 30-45 mg/day based on response	Sedation, weight gain, dry mouth	Evidence is from small studies/case series; a reasonable option once first-line measures have failed.
Difelikefalin Special situation	Moderate-to-severe uremic pruritus in hemodialysis-dependent CKD	0.5 mcg/kg IV bolus into the dialysis venous line at the end of each hemodialysis session	Dizziness, gait disturbance, hyperkalemia, falls (especially in older patients)	Nephrology/dialysis-unit initiated; the only Health Canada-approved therapy specifically for this indication.

Every drug on this table is chosen to match a specific itch mechanism. Applying a nonsedating antihistamine to non-histaminergic itch, or a topical corticosteroid to non-inflammatory itch, is a common and avoidable reason symptomatic treatment appears to fail.^[1]

Special Populations

Pregnancy: a distinct group of pregnancy-specific pruritic conditions exists -- pruritic urticarial papules and plaques of pregnancy, prurigo of pregnancy, pemphigoid gestationis, intrahepatic cholestasis of pregnancy, and pruritic folliculitis of pregnancy -- and their specific assessment and treatment is outside the scope of this chapter; any pregnant patient with new pruritus, particularly with a palms/soles pattern worse at night, needs prompt evaluation for intrahepatic cholestasis of pregnancy given fetal risk (see Red Flags & Refer). For pruritus of the causes covered in this chapter: general skin-care measures, colloidal oatmeal baths, and limited topical use of menthol or camphor are all considered low risk in pregnancy given minimal systemic absorption at these concentrations. Cetirizine and loratadine are the preferred nonsedating antihistamines in pregnancy; fexofenadine and desloratadine are reasonable alternatives. If a sedating first-generation antihistamine is wanted for sleep, chlorpheniramine, diphenhydramine, and hydroxyzine have the most accumulated safety experience in pregnancy. Cholestyramine and colestipol are not systemically absorbed and do not pose a direct fetal risk, but prolonged use can reduce maternal absorption of fat-soluble vitamins -- monitor with extended use. Rifampin is used in pregnancy for tuberculosis with no clear signal of fetal harm, though prophylactic vitamin K around delivery is standard when it is used for that indication; extrapolate this caution if used for cholestatic itch. Data on gabapentin, pregabalin, and naltrexone in human pregnancy are insufficient to establish safety -- avoid unless the benefit clearly outweighs the uncertainty, and prefer better-characterized options first. There is no safety information available for difelikefalin in pregnancy.^[1]

Breastfeeding

General measures remain first-line, and care should be taken to keep an infant's skin away from any area treated with a topical product. Colloidal oatmeal baths, and limited topical menthol/camphor use, are considered low risk given minimal systemic absorption. Oral second-generation antihistamines (cetirizine, desloratadine, fexofenadine, loratadine) are compatible with breastfeeding. Occasional use of a first-generation antihistamine is generally fine; larger or prolonged doses can cause infant drowsiness or reduce milk supply. Cholestyramine and colestipol are considered safe. Gabapentin produces low levels in breast milk, though infant monitoring is reasonable; data on pregabalin are more limited. Rifampin levels in milk are low and it is used routinely in breastfeeding patients being treated for tuberculosis. Naltrexone transfers minimally into breast milk and is not generally considered a reason to avoid breastfeeding, though data remain limited. There is no safety information available for difelikefalin in breastfeeding.

Pediatrics

Camphor-containing topical products should be avoided in children under 2 years of age -- camphor absorbed through infant skin has been associated with systemic toxicity, including seizures. Topical corticosteroid potency and duration should be minimized in children generally, given a higher surface-area-to-weight ratio and correspondingly greater systemic absorption risk than in adults.

Renal and hepatic impairment

Gabapentin and pregabalin both require dose reduction in renal impairment given renal elimination -- confirm current renal function before dosing and reduce accordingly; this is especially relevant since renal impairment is itself one of the leading indications for a gabapentinoid in this chapter. Rifampin requires baseline and periodic liver enzyme monitoring given its hepatotoxicity risk, and should be avoided or used with particular caution in patients with significant baseline hepatic impairment -- discuss with the prescribing team when itch is hepatic in origin and the liver is already compromised.

Monitoring & Follow-Up

Reassess itch severity, sleep quality, and overall impact on daily function at every follow-up -- these are the practical measures of whether treatment is working, more so than any single lab value. Confirm adherence to general skin-care measures before assuming a pharmacologic option has failed. Monitor for adverse effects specific to the agent in use: skin atrophy and thinning with topical corticosteroid use (examine the treated area), renal function and sedation/dizziness with gabapentinoid dosing, liver enzymes with rifampin or naltrexone, and for signs of opioid withdrawal if naltrexone is started in a patient who may be taking an opioid for another reason. Periodically trial tapering or discontinuing symptomatic antihistamine therapy to confirm ongoing need rather than continuing indefinitely by default. Watch for emergence of red-flag features that were not present at initial assessment -- new weight loss, jaundice, or lymphadenopathy warrants the same urgent work-up described in Red Flags & Refer even in a patient already being treated symptomatically.

Treatment Failure / Next Step

Reconfirm the working diagnosis and that adherence to the current regimen, including general skin-care measures, has genuinely been adequate before concluding a drug has failed.
Confirm a topical corticosteroid is not being used for itch without an inflammatory component -- this will not work and should be stopped rather than escalated.
Re-review the medication list for a drug started or changed around the time itch began, including anything added since the last visit.
If no systemic work-up has yet been done, or it was limited, revisit the differential-diagnosis table in Assessment & Diagnosis and pursue directed testing based on any clues that have since emerged.
If a topical-only approach has had an adequate trial without benefit, move to a systemic agent selected by the itch's likely mechanism -- gabapentinoid for neuropathic/uremic, bile acid sequestrant progressing to rifampin then naltrexone for cholestatic, updosed antihistamine for histamine-mediated, mirtazapine for nocturnal/refractory.
If a gabapentinoid has not yet been tried for a neuropathic or uremic pattern, or the itch is not clearly histamine-mediated, this is a reasonable next step given genuine trial evidence versus continued reliance on an antihistamine.
Refer to dermatology for consideration of phototherapy, or to the relevant specialist (nephrology, hepatology, hematology, psychiatry) when the itch is clearly tied to their domain and remains refractory.
For pruritus that remains unexplained and refractory despite a complete, guideline-directed work-up and adequate sequential drug trials, refer for specialist reassessment of the diagnosis itself -- pruritus of unknown origin is a diagnosis of exclusion that should be revisited periodically, not a permanent label applied once and never reconsidered.

Common Errors to Avoid

Reflexively prescribing a nonsedating antihistamine for chronic itch that is not histamine-mediated -- the evidence for benefit outside urticaria/dermatographism/mastocytosis is weak, and this delays effective treatment.^[1]
Using a topical corticosteroid for itch without visible inflammation -- it will not relieve the itch and exposes the patient to atrophy risk for no benefit.
Assuming itch without a rash cannot be drug-induced -- several important causes of drug-induced pruritus, including opioids, occur without any visible skin eruption.
Stopping the diagnostic work-up after a single negative skin examination when systemic clues (weight loss, jaundice, lymphadenopathy, abnormal labs) are present -- these need active pursuit, not reassurance.
Ordering a broad systemic panel in a patient who already has a clear primary dermatologic explanation on examination -- unnecessary and delays the correct, targeted treatment.
Using a camphor-containing product in a child under 2 years of age.
Starting naltrexone in a patient taking an opioid analgesic without checking first -- precipitates withdrawal.
Neglecting fat-soluble vitamin status with prolonged bile acid sequestrant use.
Missing intrahepatic cholestasis of pregnancy in a pregnant patient with new pruritus, especially a palms/soles pattern worse at night -- this is a red flag requiring prompt obstetric assessment, not routine symptomatic treatment.
Not counselling on the scratch-itch cycle and practical measures (short nails, cool environment, avoiding hot showers) -- these meaningfully help regardless of the underlying cause and are frequently skipped in favour of jumping straight to a prescription.

Clinical Decision Algorithm

Initial assessment

New or chronic itch presentation

Examine the skin: is there a primary rash/lesion that explains the itch?

Primary skin finding present

Diagnose and treat the specific dermatologic cause; add topical antipruritic measures adjunctively

No primary skin finding (only secondary changes, or normal skin)

Screen history and examination for red-flag/systemic clues

Red flags present

Escalate per Red Flags & Refer; pursue targeted work-up for the suspected systemic cause

No red flags

Directed work-up per the systemic differential: CBC, LFTs with bilirubin, renal function, TSH, HIV, full medication review

Cause identified

Treat the underlying cause specifically (renal, hepatic, hematologic, endocrine, drug-induced) plus adjunctive antipruritic therapy

Work-up negative

General skin care plus a trial of topical antipruritic therapy

Persistent despite an adequate trial: move to systemic therapy selection (see Systemic Therapy Selection) or refer

Systemic therapy selection by itch phenotype

Generalized or moderate-to-severe pruritus persisting despite topical measures and treatment of any identified cause

Neuropathic or uremic pattern (CKD, notalgia paresthetica, brachioradial pruritus)

Gabapentin or pregabalin, renal-adjusted dose

Hemodialysis-dependent and refractory: difelikefalin at dialysis, nephrology-initiated

Cholestatic/hepatic pattern

Cholestyramine or colestipol, 1st line

Refractory: rifampin, then naltrexone if still refractory, monitoring liver enzymes throughout

Histamine-mediated/urticarial pattern (dermatographism, urticaria)

Nonsedating antihistamine, updosed up to 4-fold per current urticaria guidance if inadequate at standard dose

Nocturnal, refractory, or paraneoplastic pattern

Mirtazapine at bedtime, or a sedating antihistamine for sleep (sedation-mediated benefit, not a true antipruritic effect)

No improvement across an adequate trial of the matched option: reassess the diagnosis, confirm adherence, and refer to dermatology or the relevant specialist

Drug Tables

How to use this table: doses are adult doses and require patient-specific confirmation, including renal/hepatic adjustment. Select any drug name to open its complete Pharmasist Drug Database page. Every agent here is grouped by the itch mechanism it is actually evidence-based for -- see Choose Initial Treatment before selecting from this table.^[1]

Topical antipruritics / counterirritants

First-choice topical option for mild, non-inflammatory itch of any origin.

Drug	Dosage	Adverse effects	Comments
Camphor/menthol topical lotion	Adults and children 2 years and older: Apply to affected area(s) up to 3-4 times daily as needed	Local burning/stinging on application (expected), rare contact dermatitis	Avoid in children under 2 years and on broken skin. Cooling effect reduces itch sensation without treating the underlying cause.

Topical corticosteroids

Only appropriate when the itch has a visible inflammatory component (redness, sometimes tenderness). Choice of potency depends on site, severity, and anticipated duration of use; not recommended for chronic, generalized, or long-term use.

Drug	Dosage	Adverse effects	Comments
Triamcinolone acetonide 0.1% cream	Adults and children: Apply a thin film 1-2 times daily	Local burning, dryness; atrophy, striae, and telangiectasia with prolonged or inappropriate use, especially on the face or skin folds	Limit continuous use to 2-3 weeks on thin-skinned sites (face, neck, folds, genitals); reassess before continuing longer on the trunk/limbs.

Topical calcineurin inhibitors

Non-steroidal option for inflammatory itch, particularly useful on sensitive sites where a corticosteroid should be minimized.

Drug	Dosage	Adverse effects	Comments
Pimecrolimus 1% cream	Adults and children 3 months and older: Apply twice daily to affected area	Transient burning/stinging/tingling at the application site, usually improving within days	Effective for itch of a variety of origins with an inflammatory component.
Tacrolimus ointment 0.03%/0.1%	Pediatric, 2 years and older: 0.03% ointment, apply twice daily Adults, 16 years and older: 0.03% or 0.1% ointment, apply twice daily	Transient burning/stinging/tingling at the application site, usually improving within days	Effective for itch of a variety of origins with an inflammatory component. Not linked to a monograph on this platform -- the formulation and Canadian pediatric-vs-adult strength selection should be confirmed against the current product monograph before use.

Substance P / neurogenic-acting topical agents

For genuinely localized neuropathic itch, or as an adjunct in other itch types; must be used consistently to work.

Drug	Dosage	Adverse effects	Comments
Capsaicin cream	Adults: Apply to affected area at least 3-4 times daily	Marked burning/stinging/erythema on initial application, common but typically decreases with repeated regular use	Blocks C-fibre conduction and depletes substance P from peripheral sensory nerve endings; initial burning frequently causes early discontinuation before benefit appears -- counsel on this explicitly.

Oral antihistamines -- nonsedating

Reliably effective only for histamine-mediated itch (urticaria, dermatographism, mastocytosis); weak evidence for benefit in most other chronic pruritus.

Drug	Dosage	Adverse effects	Comments
Cetirizine	Adults: 10 mg PO once daily; may updose up to 4-fold per current urticaria guidance	Mild sedation at standard dose, more with updosing	Can be updosed up to 4-fold for inadequate response in chronic urticaria per current urticaria guidance.
Loratadine	Adults: 10 mg PO once daily	Generally minimal sedation at standard dose	Similar efficacy profile to cetirizine for histamine-mediated itch.
Desloratadine	Adults: 5 mg PO once daily	Generally minimal sedation at standard dose	Active metabolite of loratadine.
Fexofenadine	Adults: 180 mg PO once daily	Generally minimal sedation at standard dose	Least sedating agent in this class for patients where daytime alertness is a priority.

Evidence note: updosing a nonsedating antihistamine up to 4-fold for an inadequate response is supported by current international urticaria guidance.^[2]

Oral antihistamines -- sedating

Benefit for non-histaminergic chronic itch, particularly at night, is thought to come from sedation rather than a true antipruritic effect -- set expectations accordingly.

Drug	Dosage	Adverse effects	Comments
Hydroxyzine	Adults: 25-50 mg PO at bedtime	Marked sedation, anticholinergic effects (dry mouth, constipation, urinary retention); caution in older adults	Commonly used at bedtime for nocturnal itch of any cause.
Diphenhydramine	Adults: 25-50 mg PO at bedtime	Marked sedation, anticholinergic effects; caution in older adults	Alternative sedating option; similar rationale to hydroxyzine.

Gabapentinoids

Genuine evidence base for neuropathic and uremic itch, unlike antihistamines for these causes; both require renal dose adjustment.

Drug	Dosage	Adverse effects	Comments
Gabapentin	Uremic pruritus, hemodialysis: 100 mg PO after each hemodialysis session, titrate cautiously based on response/tolerability Other neuropathic/chronic pruritus: Start 300 mg PO at bedtime, titrate over days to weeks to 900-1800 mg/day in divided doses	Sedation, dizziness, peripheral edema, ataxia	Renal dose adjustment required.
Pregabalin	Adults: Start 25-75 mg PO once or twice daily, titrate over 1-2 weeks to a usual maintenance range of 150-300 mg/day in 2 divided doses	Sedation, dizziness, peripheral edema, weight gain	Renal dose adjustment required.

Evidence note: a systematic review of gabapentin specifically for uremic pruritus in hemodialysis patients supports starting at a low dose and titrating cautiously to balance effectiveness against adverse events^[3]; a broader systematic review and meta-analysis of 27 trials found a significant reduction in pruritus with gabapentin/pregabalin compared with control, with a favourable safety profile.^[4]

Bile acid sequestrants

First-line systemic agents for cholestatic/hepatic pruritus.

Drug	Dosage	Adverse effects	Comments
Cholestyramine	Adults: Start 4 g PO once or twice daily, titrate as tolerated to a usual maximum of 16 g/day in divided doses	GI upset, constipation, bloating; interferes with absorption of other oral drugs and fat-soluble vitamins	Separate from other oral medications by at least 2-4 hours.
Colestipol	Adults: Start 5 g PO once or twice daily, titrate as tolerated up to 20-30 g/day in divided doses	GI upset, constipation, bloating; interferes with absorption of other oral drugs and fat-soluble vitamins	Alternative bile acid sequestrant when cholestyramine is not tolerated.

Evidence note: bile acid sequestrant dosing for cholestatic pruritus reflects current AASLD practice guidance.^[5]

Rifamycin (cholestatic pruritus, refractory)

Second-line, after an adequate trial of a bile acid sequestrant; requires monitoring given hepatotoxicity risk.

Drug	Dosage	Adverse effects	Comments
Rifampin	Adults: 150-300 mg PO twice daily	Hepatotoxicity, orange discolouration of urine/tears/sweat, numerous CYP450 drug interactions	Restrict to patients with normal baseline AST/ALT; up-titrate slowly over about 2 weeks with monitoring.

Evidence note: rifampin dosing for cholestatic pruritus reflects current AASLD practice guidance.^[5]

Opioid receptor modulators

For cholestatic itch refractory to the above (naltrexone), and for uremic itch specifically approved for hemodialysis patients (difelikefalin).

Drug	Dosage	Adverse effects	Comments
Naltrexone	Adults: Start 12.5 mg PO daily, titrate gradually to a usual target of 50 mg PO daily	Opioid-withdrawal-like reaction on initiation (nausea, cramping, anxiety), hepatotoxicity	Contraindicated with concurrent opioid analgesic use -- precipitates withdrawal. Monitor liver enzymes.
Difelikefalin	Adults on hemodialysis: 0.5 mcg/kg IV bolus into the venous line of the dialysis circuit at the end of each hemodialysis session	Dizziness, gait disturbance/falls, hyperkalemia, somnolence	Health Canada-approved specifically for moderate-to-severe pruritus associated with chronic kidney disease in adult hemodialysis patients; administered by the dialysis unit.

Evidence note: naltrexone dosing for cholestatic pruritus reflects current AASLD practice guidance^[5]; difelikefalin dosing reflects its Health Canada-approved regimen for hemodialysis-associated pruritus.^[6]

Antidepressants and serotonin-pathway agents

Options for nocturnal, cholestatic, paraneoplastic, or otherwise refractory itch; evidence is generally from smaller studies than for the agents above.

Drug	Dosage	Adverse effects	Comments
Mirtazapine	Adults: 15 mg PO at bedtime, may increase to 30-45 mg/day based on response	Sedation, increased appetite/weight gain, dry mouth	Reasonable option for nocturnal or refractory itch once first-line measures have failed.
Doxepin (oral, low dose)	Adults: 10-25 mg PO at bedtime	Sedation, anticholinergic effects; caution in older adults and with cardiac conduction abnormalities	Potent combined H1/H2 antihistaminic activity at low dose is thought to underlie its antipruritic effect distinct from its antidepressant use.
Sertraline	Adults: Start 25-50 mg PO once daily, titrate as tolerated to a usual antipruritic range of 75-100 mg/day	GI upset, insomnia or somnolence, sexual dysfunction	An option for cholestatic and paraneoplastic pruritus, generally better tolerated than doxepin/mirtazapine where sedation is undesirable.
Paroxetine	Adults: 20 mg PO once daily	GI upset, sedation, sexual dysfunction, discontinuation symptoms if stopped abruptly	Evidence specifically for non-dermatological (paraneoplastic, cholestatic, drug-induced) pruritus from a randomized controlled trial.
Ondansetron	Adults: 4-8 mg PO/IV, per current product dosing guidance	Headache, constipation, QT prolongation at higher doses	Evidence for benefit in chronic pruritus is inconsistent across trials -- a reasonable adjunct trial for cholestatic or opioid-induced itch rather than a reliable first choice.

Evidence note: mirtazapine dosing is based on small pilot-study evidence for nocturnal pruritus^[7]; sertraline is supported by current AASLD practice guidance for cholestatic pruritus^[5]; paroxetine dosing reflects a randomized controlled trial specifically in non-dermatological pruritus.^[8]

References

European S2k Guideline on Chronic Pruritus — Acta Dermato-Venereologica, in cooperation with the European Dermatology Forum (Weisshaar E, Muller S, Szepietowski JC, Dalgard F, Garcovich S, Kupfer J, Gimenez-Arnau A, Lambert J, Mettang T, Misery L, Savk E, Tschachler E, Wallengren J, Stander S). Acta Derm Venereol 2025;105:adv44220
The international EAACI/GA2LEN/EuroGuiDerm/APAAACI guideline for the definition, classification, diagnosis and management of urticaria — Allergy (Zuberbier T, Latiff AHA, Abuzakouk M, et al.). Allergy 2022;77(3):734-766
Gabapentin for uremic pruritus in hemodialysis patients: a qualitative systematic review — Canadian Journal of Kidney Health and Disease (Lau T, Leung S, Lau W). Can J Kidney Health Dis 2016;3:14
Efficacy and Safety of Pregabalin and Gabapentin for Pruritus: A Systematic Review and Meta-Analysis — Journal of Pain and Symptom Management. J Pain Symptom Manage 2024
Primary Biliary Cholangitis: 2018 Practice Guidance from the American Association for the Study of Liver Diseases — Hepatology, American Association for the Study of Liver Diseases (Lindor KD, Bowlus CL, Boyer J, Levy C, Mayo M). Hepatology 2019;69(1):394-419
Summary Basis of Decision - KORSUVA (difelikefalin) — Health Canada. Health Canada Summary Basis of Decision, 2022
Mirtazapine for reducing nocturnal itch in patients with chronic pruritus: a pilot study — Journal of the American Academy of Dermatology (Hundley JL, Yosipovitch G). J Am Acad Dermatol 2004;50(6):889-891
Paroxetine in the treatment of severe non-dermatological pruritus: a randomized, controlled trial — Journal of Pain and Symptom Management (Zylicz Z, Krajnik M, Sorge AA, Costantini M). J Pain Symptom Manage 2003;26(6):1105-1112

Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.