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Indications and Dosage
Oral
Allergic conditions Adult: 1 mg bid, increased up to Max 6 mg daily, if necessary. Max treatment duration: 14 days.
Child: 1-3 years 250-500 mcg bid; 3-6 years 500 mcg bid; 6-12 years 500-1000 mcg bid. |
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Administration
May be taken with or without food. May be taken w/ meals to reduce GI discomfort.
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Contraindications
Lower respiratory disease including asthma, porphyria. Premature infants, neonates and children <1 year. Lactation. Concomitant use with MAOIs.
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Special Precautions
Patients with history of asthma; CV diseases (e.g. hypertension, ischaemic heart disease); increased intra-ocular pressure or narrow-angle glaucoma; prostatic hypertrophy, bladder neck obstruction and/or genitourinary obstruction; pyloroduodenal obstruction including stenotic peptic ulcer; thyroid dysfunction; epilepsy or history of seizures. Children and elderly. Pregnancy.
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Adverse Reactions
Significant: CNS depression (e.g. sedation, dizziness, drowsiness).
Gastrointestinal disorders: Epigastric distress. General disorders and administration site conditions: Fatigue. Nervous system disorders: Headache. |
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Patient Counseling Information
This drug may cause dizziness, drowsiness, and visual disturbances, if affected, do not drive or operate machinery.
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Overdosage
Symptoms: CNS depression to stimulation, depressed level of consciousness, excitability, hallucinations, or convulsions. Anticholinergic symptoms (dry mouth, mydriasis, flushing, gastrointestinal reactions, and tachycardia) may occur. Management: Symptomatic treatment. Induce vomiting by giving a glass of water or milk. Perform gastric lavage with isotonic and 1/2 isotonic saline within 3 hours after ingestion. May give vasopressors in case of hypotension.
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Drug Interactions
May potentiate anticholinergic activity of atropine and TCAs.
Potentially Fatal: Severe sedation and CNS depression with other CNS depressants (e.g. MAOIs, hypnotics, anxiolytics, opioid analgesics). |
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Food Interaction
Avoid alcohol.
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Action
Description:
Mechanism of Action: Clemastine competitively blocks H1-receptors sites on effector cells of the gastrointestinal tract, blood vessels and respiratory tract. Onset: 2 hours. Duration: 10-12 hours, up to 24 hours. Pharmacokinetics: Absorption: Rapidly and almost completely absorbed from gastrointestinal tract. Bioavailability: Approx 40%. Time to peak plasma concentration: 2-4 hours. Distribution: Enters the breast milk. Volume of distribution: Approx 800 L. Plasma protein binding: 95%. Metabolism: Metabolised in the liver via O-dealkylation followed by alcohol degradation, aliphatic, aromatic, and direct oxidation. Subject to significant first pass metabolism. Excretion: Mainly via urine (approx 42% as metabolites). Elimination half-life: Approx 21 hours. |
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Chemical Structure
 Source: National Center for Biotechnology Information. PubChem Database. Clemastine, CID=26987, https://pubchem.ncbi.nlm.nih.gov/compound/Clemastine (accessed on Jan. 21, 2020) |
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Storage
Store between 20-25°C.
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MIMS Class
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ATC Classification
R06AA04 - clemastine ; Belongs to the class of aminoalkyl ethers used as systemic antihistamines.
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References
Anon. Clemastine. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 28/03/2019. Buckingham R (ed). Clemastine. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 28/03/2019. Clemastine Fumarate Tablet (Teva Pharmaceuticals USA, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 28/03/2019. Joint Formulary Committee. Clemastine. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 28/03/2019.
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