Clemastine

Mechanism-of-action class: Histamine H1 Receptor Antagonists.

• Clemastine Fumarate Syrup is indicated for the relief of symptoms associated with allergic rhinitis such as sneezing, rhinorrhea, pruritus and lacrimation. Clemastine Fumarate Syrup is indicated for use in pediatric populations (age 6 years through 12) and adults (see DOSAGE AND ADMINISTRATION ).ICD-10: J30.9

• Antihistamines are contraindicated in patients hypersensitive to the drug or to other antihistamines of similar chemical structure (see PRECAUTIONS- Drug Interactions ). Antihistamines should not be used in newborn or premature infants .contraindicated

DOSAGE SHOULD BE INDIVIDUALIZED ACCORDING TO THE NEEDS AND RESPONSE OF THE PATIENT. Pediatric Children aged 6 to 12 years For Symptoms of Allergic Rhinitis The starting dose is 1 teaspoonful (0.5 mg clemastine) twice daily. Since single doses of up to 2.25 mg clemastine were well tolerated by this age group, dosage may be increased as required, but not to exceed 6 teaspoonfuls daily (3 mg clemastine). For Urticaria and Angioedema The starting dose is 2 teaspoonfuls (1 mg clemastine) twice daily, not to exceed 6 teaspoonfuls daily (3 mg clemastine). Adults and Children 12 Years and Over For Symptoms of Allergic Rhinitis The starting dose is 2 teaspoonfuls (1 mg clemastine) twice daily. Dosage may be increased as required, but not to exceed 12 teaspoonfuls daily (6 mg clemastine). For Urticaria and Angioedema The starting dose is 4 teaspoonfuls (2 mg clemastine) twice daily, not to exceed 12 teaspoonfuls daily (6 mg clemastine).

Antihistamines should be used with considerable caution in patients with: narrow angle glaucoma, stenosing peptic ulcer, pyloroduodenal obstruction, symptomatic prostatic hypertrophy, and bladder neck obstruction. Use with CNS Depressants Clemastine has additive effects with alcohol and other CNS depressants (hypnotics, sedatives, tranquilizers, etc.). Use in Activities Requiring Mental Alertness Patients should be warned about engaging in activities requiring mental alertness such as driving a car or operating appliances, machinery, etc. Use in the Elderly (approximately 60 years or older) Antihistamines are more likely to cause dizziness, sedation, and hypotension in elderly patients.

The most frequent adverse reactions are italicized: Nervous System Sedation , sleepiness , dizziness , disturbed coordination , fatigue, confusion, restlessness, excitation, nervousness, tremor, irritability, insomnia, euphoria, paresthesia, blurred vision, diplopia, vertigo, tinnitus, acute labyrinthitis, hysteria, neuritis, convulsions. Gastrointestinal System Epigastric distress , anorexia, nausea, vomiting, diarrhea, constipation. Respiratory System Thickening of bronchial secretions , tightness of chest and wheezing, nasal stuffiness. Cardiovascular System Hypotension, headache, palpitations, tachycardia, extrasystoles. Hematologic System Hemolytic anemia, thrombocytopenia, agranulocytosis. Genitourinary System Urinary frequency, difficult urination, urinary retention, early menses. General Urticaria, drug rash, anaphylactic shock, photosensitivity, excessive perspiration, chills, dryness of mouth, nose and throat. To report SUSPECTED ADVERSE REACTIONS, contact Allucent at 1-866-511-6754 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Pregnancy Teratogenic Effects Pregnancy Category B Oral reproduction studies performed with clemastine fumarate in rats and rabbits at doses up to 312 and 188 times the adult human doses respectively, have revealed no evidence of teratogenic effects. There are no adequate and well-controlled studies of clemastine fumarate in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used in pregnancy only if clearly needed.

Metabolism

Antihistamines are well-absorbed following oral administration. Chlorpheniramine maleate, clemastine fumarate, and diphenhydramine hydrochloride achieve peak blood levels within 2-5 hours following oral administration.

Antihistamine overdosage reactions may vary from central nervous system depression to stimulation. In children, stimulation predominates initially in a syndrome which may include excitement, hallucinations, ataxia, incoordination, muscle twitching, athetosis, hyperthermia, cyanosis convulsions, tremors, and hyperreflexia followed by postictal depression and cardio-respiratory arrest. Convulsions in children may be preceded by mild depression. Dry mouth, fixed dilated pupils, flushing of the face, and fever are common. In adults, CNS depression, ranging from drowsiness to coma, is more common. The convulsant dose of antihistamines lies near the lethal dose. Convulsions indicate a poor prognosis. In both children and adults, coma and cardiovascular collapse may occur. Deaths are reported especially in infants and children. There is no specific therapy for acute overdosage with antihistamines. The latent period from ingestion to appearance of toxic effects is characteristically short (1/2-2 hours). General symptomatic and supportive measures should be instituted promptly and maintained for as long as necessary. Since overdoses of other classes of drugs (i.e.

• Jan 31, 1992ANDAANDA073283Genus
• Jun 30, 1994ANDAANDA073399Genus
• Dec 17, 1997ANDAANDA074884New Heightsrx

1. 1Dyspnoea1088.2%
2. 2Pyrexia1007.6%
3. 3Off Label Use836.3%
4. 4Erythema785.9%
5. 5Nausea765.7%
6. 6Diarrhoea745.6%
7. 7Constipation675.1%
8. 8Rash675.1%
9. 9Sepsis644.8%
10. 10Fatigue614.6%
11. 11Pneumonia614.6%
12. 12Toxic Epidermal Necrolysis604.5%
13. 13Vomiting574.3%
14. 14Abdominal Pain544.1%
15. 15Covid-19513.9%

Recent PubMed references pinned to Clemastine as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

• Clemastine fumarate promotes myelin repair in a nonhuman primate model of demyelination characterized by absent spontaneous remyelination.
  Proceedings of the National Academy of Sciences of the United States of America · 2026 · Sarrazin N, Arab R, Cordano C, et al.
  PMID 41719338DOI 10.1073/pnas.2520161123
• The Cambridge Centre for Myelin Repair trial Two (CCMR Two): a trial protocol for a phase 2a, randomised, double-blind, placebo-controlled clinical trial of the ability of the combination of metformin and clemastine to promote remyelination in people with relapsing-remitting multiple sclerosis already on disease-modifying therapy.
  Trials · 2025 · Riboni-Verri G, McMurran CE, Mukherjee T, et al.
  PMID 41361285DOI 10.1186/s13063-025-09254-2
• Evaluating the effects of pro-myelinating drugs on motor function and myelination in a zebrafish model of genetic leukoencephalopathy.
  Neuroscience letters · 2025 · Banerjee S, Berry Y, Fisher E, et al.
  PMID 40456507DOI 10.1016/j.neulet.2025.138280
• Clemastine fumarate accelerates accumulation of disability in progressive multiple sclerosis by enhancing pyroptosis.
  The Journal of clinical investigation · 2025 · Kocot J, Kosa P, Ashida S, et al.
  PMID 40371642DOI 10.1172/JCI183941
• Clemastine enhances myelin formation in the striatum and medial prefrontal cortex and improves sociability in a neonatal rat hypoxic-ischemic model.
  Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie · 2025 · Feng Y, Ma X, Zong X, et al.
  PMID 40058153DOI 10.1016/j.biopha.2025.117916
• Emerging therapeutic application of clemastine: a review of recent patents updates.
  Naunyn-Schmiedeberg's archives of pharmacology · 2025 · Soni S, Kaur G
  PMID 40055203DOI 10.1007/s00210-025-03978-3
• Clemastine attenuates subarachnoid haemorrhage pathology in a mouse model via Nrf2/SQSTM1-mediated autophagy.
  British journal of pharmacology · 2025 · Zou Y, Tao Z, Li P, et al.
  PMID 40052261DOI 10.1111/bph.17465
• Clemastine enhances exercise-induced motor improvement in hypoxic ischemic rats.
  Brain research · 2025 · Goto T, Tsurugizawa T, Komaki Y, et al.
  PMID 39362477DOI 10.1016/j.brainres.2024.149257

The 10 most recently updated of 23 ClinicalTrials.gov registrations naming Clemastine as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• Clemastine Fumarate as Remyelinating Treatment in Internuclear Ophthalmoparesis and Multiple Sclerosis
  Terminated · Phase 3 · Interventional · 47 enrolled · Amsterdam UMC, location VUmc
  NCT05338450updated 2026-05-06
• A Treatment for a Form of Age-Related Central Auditory Processing Disorder Consisting of Clemastine Fumarate Plus Engineered Sound
  Recruiting · Phase 1 · Phase 2 · Interventional · 344 enrolled · University of Colorado, Denver
  NCT07304024updated 2026-04-30
• Clemastine Fumarate in the Treatment of Neurodevelopmental Delays in Williams Syndrome
  Completed · Phase 2 · Interventional · 28 enrolled · Qilu Hospital of Shandong University
  NCT06315699updated 2026-03-19
• Assessing Changes in Multi-parametric MRI in MS Patients Taking Clemastine Fumarate as a Myelin Repair Therapy
  Recruiting · Phase 1 · Phase 2 · Interventional · 74 enrolled · University of California, San Francisco
  NCT05359653updated 2026-03-11
• Assessment of Clemastine Fumarate as a Remyelinating Agent in Acute Optic Neuritis (ReCOVER)
  Recruiting · Phase 2 · Interventional · 90 enrolled · University of California, San Francisco
  NCT02521311updated 2026-03-11
• Assessing Changes in Multi-parametric MRI in Patients With Acute Demyelinating Lesions Taking Clemastine Fumarate as a Myelin Repair Therapy
  Not yet recruiting · Phase 1 · Phase 2 · Interventional · 44 enrolled · University of California, San Francisco
  NCT06065670updated 2026-03-11
• Clemastine Treatment in Individuals With Williams Syndrome
  Active not recruiting · Phase 2 · Interventional · 30 enrolled · Sheba Medical Center
  NCT06087757updated 2026-03-06
• CCMR Two: A Phase IIa, Randomised, Double-blind, Placebo-controlled Trial of the Ability of the Combination of Metformin and Clemastine to Promote Remyelination in People With Relapsing-remitting Multiple Sclerosis Already on Disease-modifying Therapy
  Completed · Phase 2 · Interventional · 70 enrolled · Cambridge University Hospitals NHS Foundation Trust
  NCT05131828updated 2025-12-11
• Assessment of Clemastine Fumarate as a Remyelinating Agent in Multiple Sclerosis
  Completed · Phase 2 · Interventional · 50 enrolled · University of California, San Francisco
  NCT02040298updated 2025-09-17
• Clemastine for Improving White Matter and Boosting Antidepressant Response in Late-life Depression
  Not yet recruiting · Phase 2 · Interventional · 80 enrolled · University of Illinois at Chicago
  NCT06591091updated 2025-09-04

Frequently asked questions

How does Clemastine work?

Mechanism-of-action class: Histamine H1 Receptor Antagonists.

What is Clemastine used for?

According to FDA labeling, Clemastine carries indications including: Clemastine Fumarate Syrup is indicated for the relief of symptoms associated with allergic rhinitis such as sneezing, rhinorrhea, pruritus and lacrimation. Clemastine Fumarate Syrup is indicated for use in pediatric populations (age 6 years through 12) and adults (see DOSAGE AND ADMINISTRATION ).. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What class of drug is Clemastine?

Clemastine is classified as Aminoalkyl ethers, Antihistamines for topical use, Histamine H1 Receptor Antagonists, Decreased Histamine Activity.

What are the brand names for Clemastine?

Clemastine is marketed under brand names including Clemasz, Clemsza, Dayhist-1, Tavist, Wal-Hist 12 HR Relief.

What are the contraindications for Clemastine?

Clemastine labeling lists contraindications including: Antihistamines are contraindicated in patients hypersensitive to the drug or to other antihistamines of similar chemical structure (see PRECAUTIONS- Drug Interactions ). Antihistamines should not be used in newborn or premature infants .. Always consult the full prescribing information and a clinician.