Clemastine
Clemastine is an antihistamine used to relieve allergy symptoms and certain allergic skin reactions, available as an oral solution and tablet.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 4 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
📖 Clemastine: Patient Information Guide
A plain-language walkthrough of Clemastine — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.
🎯What it's used for▾
Clemastine is an antihistamine used to relieve allergic symptoms and treat certain allergic skin reactions. Supported uses across products include:
- Allergic rhinitis symptoms — sneezing, runny nose (rhinorrhea), nasal and eye itching (pruritus), and watery eyes (lacrimation) — in adults and children aged 6 and older (Clemastine Fumarate oral solution supports use in children aged 6–12; tablets are indicated for adults)
- Mild, uncomplicated urticaria (hives) — in adults, supported by Clemastine Fumarate tablets and Clemsza tablets, and by Clemastine Fumarate oral solution at the appropriate dose
- Mild, uncomplicated angioedema (allergic skin swelling) — same products and dosage level as for hives
⚙️How it works▾
Clemastine blocks H1 receptors — the specific sites in your body where histamine attaches during an allergic reaction. By occupying those receptor sites, it prevents histamine from triggering the chain of reactions that cause itching, swelling, redness, and congestion. It does not stop histamine from being released, but it does stop histamine from having its usual effect. Clemastine also has anticholinergic activity, meaning it has mild drying effects — helpful for a runny nose, but also responsible for side effects like dry mouth and urinary difficulties.
💊How it's taken▾
Clemastine is taken by mouth in either tablet or oral solution form. It is generally taken twice daily, though tablets may be taken up to three times daily as needed. Dosing is always individualized based on your age, the condition being treated, and how you respond.
- Clemastine Fumarate oral solution is measured in teaspoonfuls and is appropriate for adults and children aged 6 through 12
- Clemastine Fumarate tablets and Clemsza tablets are for adults; a single dose may be sufficient, repeated as needed up to three times per day maximum
Always follow your prescriber's instructions. Do not exceed the maximum daily amount listed for your specific product.
🤒Side effects — in detail▾
The most common side effect is drowsiness, which can be significant enough to require stopping treatment. Other frequently reported effects include:
- Dry mouth, nose, or throat
- Dizziness or disturbed coordination
- Headache
- Nausea, upset stomach, or constipation
- Blurred vision
- Difficulty or painful urination
- Restlessness or excitation (more common in children)
- Thickening of mucus in the airways
More serious reactions — including rapid heartbeat, severe allergic reactions (anaphylaxis), blood cell abnormalities, or convulsions — are rare but require immediate medical attention.
⚠️Warnings & precautions▾
- Drowsiness and impaired alertness: Clemastine can significantly impair your ability to drive or operate machinery. This risk is much greater if you also use alcohol, sedatives, or other CNS depressants.
- Certain pre-existing conditions: Use with considerable caution if you have narrow-angle glaucoma, an enlarged prostate, bladder obstruction, a stomach ulcer, or intestinal blockage — clemastine's anticholinergic effects can worsen these.
- Older adults: People around age 60 and older face a higher risk of dizziness, sedation, and low blood pressure with this medication.
- Children under 12: Safety and effectiveness of the tablet form have not been established for children under 12. The oral solution is specifically formulated for children aged 6–12 at appropriate doses.
- Pregnancy: There is not enough human data to confirm safety in pregnancy — discuss the risks and benefits with your doctor.
- Breastfeeding: Clemastine is contraindicated (must not be used) while breastfeeding, due to higher risks for infants, especially newborns and premature babies.
🔀What it interacts with▾
Clemastine can interact with several types of drugs and substances. Key interactions to know:
- Alcohol — adds to sedation and CNS depression; the combination can be significantly impairing
- Sedatives, tranquilizers, and hypnotics (sleep aids) — combined drowsiness is amplified
- Barbiturates — increased CNS depression when taken together
- MAO inhibitors (MAOIs) — a class of antidepressants that prolongs and intensifies clemastine's anticholinergic (drying) effects; this combination is contraindicated
- Other CNS depressants — any drug that causes sedation can add to clemastine's effects
This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.
📋Before taking it▾
- Do not use if you are breastfeeding — clemastine passes into breast milk and poses risks to infants, especially newborns and premature babies
- Do not use to treat asthma or other lower respiratory tract conditions
- Do not take if you are allergic to clemastine or chemically similar antihistamines
- Do not take if you are currently using an MAO inhibitor (MAOI) antidepressant
- Tell your prescriber if you have narrow-angle glaucoma, enlarged prostate, difficulty urinating, or bladder obstruction
- Tell your prescriber if you have a stomach ulcer or any bowel blockage
- If you are pregnant, discuss with your doctor — potential effects on the developing baby are not well established
- Older adults should be monitored closely for dizziness, low blood pressure, and sedation
🚑If you take too much▾
Taking too much clemastine can affect the nervous system — in adults, this most often means heavy drowsiness up to coma; in children, overstimulation (excitement, hallucinations, muscle twitching, seizures) can occur first, followed by serious depression of the nervous system. Signs of overdose can appear within 30 minutes to 2 hours of ingestion. If you suspect an overdose, seek emergency medical care immediately — there is no specific antidote, and treatment focuses on supportive care and managing symptoms.
📡Pharmacodynamics — effects in the body▾
Clemastine works by blocking H1 histamine receptors throughout the body. This reduces the classic allergy responses that histamine drives: capillary leakiness (which causes swelling), the itch-and-flare reaction in the skin, and tightening of smooth muscles in the gut and airways. Its antihistamine effect peaks roughly 5–7 hours after a dose and can last 10–12 hours, and sometimes up to 24 hours. Clemastine also has anticholinergic (drying) properties and can cause sedation through effects on the central nervous system.
🔬Pharmacokinetics — how your body processes it▾
Clemastine is rapidly and well absorbed from the gastrointestinal tract after oral administration, with peak blood levels reached in about 2–4 hours. It is broken down (metabolized) primarily in the liver, and most of the drug and its metabolites are cleared through the urine. Small amounts can pass into breast milk. Its antihistamine effect can persist for 10–12 hours after a dose and in some people up to 24 hours.
📦How to store it▾
Store at 20° to 25°C (68° to 77°F) . Dispense in a tight, light-resistant container as defined in the USP, with a child-resistant closure (as required).
📄 Written from Clemastine’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →
Supplements & herbs that interact with Clemastine
72 supplements and herbal products have documented interactions with Clemastine in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 3
- Moderate · 57
- Minor · 12
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
🩺 Pharmacist Counseling Corner
Quick, plain-English answers to the questions patients ask most about Clemastine — the kind of thing our pharmacy team would talk through with you at the counter.
What is clemastine actually used for? ▾
Will this medication make me drowsy? ▾
Can I give clemastine to my child? ▾
Is there anything I should tell my doctor before taking clemastine? ▾
How long does clemastine take to work, and how long does it last? ▾
What should I do if I think I or someone else has taken too much? ▾
Is Clemastine available over the counter? ▾
When was Clemastine first available? ▾
Who makes Clemastine? ▾
💬 Answers drafted from Clemastine’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →
🧰 Keep exploring
💊 How Clemastine comes
Clemastine is available in 2 forms. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Oral solution
How this form is used
- Clemastine Fumarate oral solution treats allergic rhinitis symptoms (sneezing, runny nose, itching, watery eyes) in adults and children aged 6–12
- Clemastine Fumarate oral solution treats mild, uncomplicated hives (urticaria) and skin swelling (angioedema)
- Clemastine Fumarate oral solution is measured in teaspoonfuls and taken by mouth
- Clemastine Fumarate oral solution is generally taken twice daily; dosage is individualized — follow your prescriber's guidance
- Clemastine Fumarate oral solution: do not exceed the maximum daily teaspoonful amount recommended for your age group
Tablet
How this form is used
- Clemastine Fumarate tablets and Clemsza tablets treat allergic rhinitis symptoms (sneezing, runny nose, itching, watery eyes)
- Clemastine Fumarate tablets and Clemsza tablets treat mild, uncomplicated hives (urticaria) and skin swelling (angioedema)
- Clemastine Fumarate tablets and Clemsza tablets are swallowed by mouth
- Many patients respond to a single dose as needed, but tablets should not be taken more than three times daily
- Dosage is individualized — follow your prescriber's instructions and do not exceed the maximum daily amount
📊 Clemastine across the U.S. market
How Clemastine appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
FDA-listed product records by dose form (tablet variants merged) — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
Also listed with the FDA, not a patient dose form: Powder (4) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
📈 How widely Clemastine is used
A general measure of how commonly Clemastine is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Clemastine is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Clemastine prescribed? Of the 1,594 medications we measure, Clemastine ranks #1,109 by Medicaid prescriptions — more than 30% of them.
Utilization by Clemastine product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
clemastine fumarate 0.134 MG/ML Oral Solution Most dispensed
Summed across the 1 of 3 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 857430
clemastine fumarate 2.68 MG Oral Tablet
Summed across the 2 of 7 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 857461
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Clemastine, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 3 of 10 listed Clemastine NDCs with Medicaid activity.
🔍 Compare Clemastine products
A representative set of FDA-listed product records for Clemastine — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Oral solution | ||||
| 0.67 mg/5 mL | Oral | Ayurax, LLC × 2 listings | ANDA | View NDC → |
| 0.67 mg/5 mL | Oral | Chartwell RX, LLC | ANDA | View NDC → |
| 0.67 mg/5 mL | Oral | Genus Lifesciences | ANDA | View NDC → |
| 💊Tablet | ||||
| 2.68 mg | Oral | Genus Lifesciences | ANDA | View NDC → |
| 2.68 mg | Oral | IPG Pharmaceuticals, Inc. | ANDA | View NDC → |
| 2.68 mg | Oral | Teva Pharmaceuticals USA, Inc. | ANDA | View NDC → |
| 💊Bulk drug substance | ||||
| 1 g/g | — | AX Pharmaceutical Corp | BULK INGREDIENT FOR HUMAN PRESCRIPTION COMPOUNDING | View NDC → |
| 35 kg/35 kg | — | Nuray Chemicals Private Limited | BULK INGREDIENT | View NDC → |
| 1 g/g | — | Sekisui Medical Co., Ltd. | BULK INGREDIENT | View NDC → |
| 35 kg/35 kg | — | Sthree Chemicals Private Limited | BULK INGREDIENT | View NDC → |
Showing 11 of 11 products — FDA National Drug Code Directory. See every product, package size and price: browse all 11 Clemastine NDCs →
📈 What people report — real-world data (FDA FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Clemastine — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Clemastine in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
🏛️ The road to your pharmacy
How Clemastine went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
🚨 Recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
Source: openFDA drug enforcement (recall) reports.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 2578 3 dose forms · 4 strengths
-
Dose form (SCDF) Extended Release Oral Tablet RxCUI 562263No current FDA listingClinical drug / strength (SCD) 12 HR clemastine fumarate 1.34 MGRxCUI 857420 -
Dose form (SCDF) Oral Solution RxCUI 756627In current FDA listingsClinical drug / strength (SCD) fumarate 0.134 MG/MLRxCUI 857430 -
Dose form (SCDF) Oral Tablet RxCUI 371549In current FDA listings
Look up RxCUI 2578 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
📦 Supply & shortage status
Whether Clemastine is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
🏷️ Sold under these brand names
🏭 Manufacturers & labelers
RxNorm drug class
Clemastine belongs to the Antihistamines for topical use class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
🔬 Where this comes from
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How we combine label and product data
HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 4 FDA-filed SPL label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.
For canonical ingredient pages, bounded product-attributed indication and administration excerpts may be added to the AI evidence, and the generator is instructed to preserve available product, brand, route, and form qualifiers instead of treating one label as universal. Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. Genus Lifesciences is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.
This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.