clemastine

Action and Spectrum

Actions and Spectrum 

clemastine inhibits histamine’s ability to attach to H1 histamine receptors, preventing the allergic reactions that histamine causes. 

By inhibiting acetylcholine’s ability to activate muscarinic receptors, clemastine demonstrates anticholinergic effect.  

Sneezing, itching, runny nose, and nasal congestion are just a few of the allergic rhinitis symptoms that clemastine is frequently used to treat. 

Drug Interaction

Adverse Reaction

Frequency not defined  

CNS depression 

Dysuria 

Urinary retention 

Disturbed coordination  

Anorexia  

Leukopenia 

Pancytopenia 

Impotence 

Vertigo 

Diarrhea  

Wheezing 

Chills 

Thrombocytopenia 

Muscular weakness 

Nervousness, delirium, palpitation, seizures, restlessness, insomnia, tremors, euphoria is less common 

Dizziness  

Visual disturbances 

Acute labyrinthitis 

Palpitation ECG changes, Arrhythmias, Tachycardia  

Tightness of the chest 

Hypotension 

Blurred vision 

Diplopia, tinnitus 

Hypertension  

Facial dyskinesia 

Nasal stuffiness 

Toxic psychosis 

Headache 

Sweating 

Thickening of bronchial secretions 

Hypotension, dizziness and sedation may occur in geriatric patients 

Dryness of mouth, throat and nose 

Lassitude  

Paresthesia 

Hemolytic anemia  

Early menses 

Faintness 

Agranulocytosis 

Nervousness 

Irritability 

Nausea 

Vomiting  

Cholestasis, hepatic function abnormality, jaundice, hepatitis, hepatic failure is rare 

Insomnia 

Tremors 

Pruritus, inflammation, rash, eczema, erythema on exposed skin may occur with topical formulation 

Constipation 

Epigastric distress 

Drowsiness 

Sedation ranging from mild drowsiness to deep sleep  

Black Box Warning

Black Box Warning 

None  

Contraindication / Caution

Contraindication/Caution: 

Contraindication: 

• clemastine should not be used in individuals who have a known hypersensitivity or allergy to clemastine. 

Caution: 

• When engaging in activities like driving that call for mental clarity, caution should be used.  
• For those who have glaucoma, clemastine may raise intraocular pressure, which can be harmful. In people like these, it should be applied with caution. 
• Precautions for pyloroduodenal blockage, prostatic hypertrophy, stenosing peptic ulcer, and narrow angle glaucoma. 

Pregnancy / Lactation

Pregnancy warnings:     

Pregnancy category: B 

Lactation: Enters human breast milk and it is not recommended  

Pregnancy Categories:         

Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 

Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women.  

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women. 

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits. 

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women. 

Category N: There is no data available for the drug under this category. 

Pharmacology

Pharmacology  

First-generation antihistamine with anticholinergic effects is clemastine.  

At H1 histamine receptors, clemastine functions as a competitive antagonist. 

Pharmacodynamics 

clemastine exhibits anticholinergic effects by blocking the action of acetylcholine on muscarinic receptors. The H1 histamine receptor is specifically blocked by clemastine. 

Sedation is produced when clemastine interacts with central histamine receptors after crossing the blood-brain barrier. 

Pharmacokinetics 

Absorption   

It is well absorbed from the gastrointestinal tract after oral administration. 

Distribution 

clemastine has a high plasma protein binding capacity, primarily binding to albumin. 

Metabolism 

clemastine undergoes extensive hepatic metabolism. 

Elimination and excretion 

clemastine and its metabolites are primarily eliminated through renal excretion. 

Adminstartion

Administration 

clemastine is administered orally in the form of tablets or syrup.

Patient Information Leaflet

Patient information leaflet 

Generic Name: clemastine 

Why do we use clemastine? 

clemastine is used to alleviate symptoms of allergic rhinitis, such as sneezing, itching, runny nose, and nasal congestion.   

clemastine is effective in relieving symptoms associated with hives, including itching, redness, and swelling.  

It can be used to alleviate symptoms of allergic conjunctivitis, such as redness, itching, and watering of the eyes.