Dosing and uses of Clemastine
Adult dosage forms and strengths
tablet
- 1.34mg
- 2.68mg
syrup
- 0.67mg/5mL
Allergic Rhinitis
1.34 mg PO q12hr; not to exceed 8.04 mg/day for syrup or 2.68 mg/24 hours for tablets
Urticaria
2.68 mg PO qDay-q8hr; not to exceed 8.04 mg/day
Angioedema
2.68 mg PO qDay-q8hr; not to exceed 8.04 mg/day
Other Indications & Uses
Perennial & seasonal allergic & vasomotor rhinitis, relief of symptoms from colds, urticaria, angioedema, anaphylactic reactions, pruritus, allergic conjunctivitis
Pediatric dosage forms and strengths
tablet
- 1.34mg
- 2.68mg
syrup
- 0.67mg/5mL
Allergic Rhinitis
<6 years old: 0.05 mg/kg/day as clemastine base or 0.335-0.67 mg/day clemastine fumarate (0.25-0.5 mg base/day) divided q8-12hr; not to exceed 1.34 mg (1 mg base)
6-12 years old: 0.67-1.34 mg clemastine fumarate (0.5-1 mg base) q12hr; not to exceed 4.02 mg/day (3 mg/day base)
>12 years old: As in adults
Urticaria
<6 years old: 0.05 mg/kg/day as clemastine base or 0.335-0.67 mg/day clemastine fumarate (0.25-0.5 mg base/day) divided q8-12hr; not to exceed 1.34 mg (1 mg base)
6-12 years old: 0.67-1.34 mg clemastine fumarate (0.5-1 mg base) q12hr; not to exceed 4.02 mg/day (3 mg/day base)
>12 years old: As in adults
Geriatric dosage forms and strengths
Administer lower doses to patients >60 years
Nonanticholinergic antihistamines should be considered first when treating allergic reactions (Beers Criteria)
Avoid use in elderly because of high incidence of anticholinergic effects
Clearance reduced with advanced age, greater risk of confusion, dry mouth, constipation, and other anticholinergic effects and toxicity
May exacerbate existing lower urinary conditions or benign prostatic hyperplasia
Allergic Rhinitis
1.34 mg PO q12hr; not to exceed 8.04 mg/day for syrup or 2.68 mg/24 hours for tablets
Urticaria
2.68 mg PO qDay-q8hr; not to exceed 8.04 mg/day
Angioedema
2.68 mg PO qDay-q8hr; not to exceed 8.04 mg/day
Clemastine adverse (side) effects
Varies in incidence & severity with the individual drug; also individual patients vary in susceptibility
Frequency not defined
CNS depression
Drowsiness
Sedation ranging from mild drowsiness to deep sleep (most frequent)
Dizziness
Lassitude
Disturbed coordination
Muscular weakness
Restlessness, insomnia, tremors, euphoria, nervousness, delirium, palpitation, seizures is less common
Epigastric distress
Anorexia
Nausea
Vomiting
Diarrhea
Constipation
Cholestasis, hepatitis, hepatic failure, hepatic function abnormality, jaundice is rare
Eczema, pruritus, inflammation, papular rash, erythema on exposed skin may occur with topical formulation
Tachycardia, palpitation ECG changes (eg, widened QRS) Arrhythmias (eg, extrasystole, heart block)
Hypotension
Hypertension
Dizziness, sedation, and hypotension may occur in geriatric patients
Dryness of mouth, nose, and throat
Dysuria
Urinary retention
Impotence
Vertigo
Visual disturbances
Blurred vision
Diplopia; tinnitus
Acute labyrinthitis
Insomnia
Tremors
Nervousness
Irritability
Facial dyskinesia
Tightness of the chest
Thickening of bronchial secretions
Wheezing
Nasal stuffiness
Sweating
Chills
Early menses
Toxic psychosis
Headache
Faintness
Paresthesia
Agranulocytosis
Hemolytic anemia
Leukopenia
Thrombocytopenia
Pancytopenia
Warnings
Contraindications
Documented hypersensitivity
Lower respiratory disease, eg, asthma (controversial)
Preemies & neonates
Nursing women
Caution
Caution in narrow angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal obstruction, or bladder neck obstruction
Pregnancy and lactation
Pregnancy category: B
Lactation: enters breast milk/not recommended
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Clemastine
Mechanism of action
Histamine H1-receptor antagonist in blood vessels, respiratory tract, and gastrointestinal tract
Pharmacokinetics
Onset: 5-7 hr
Duration: 8-12 hr
Peak Plasma Time: 2-5 hr
Vd: 800 L
Metabolism: Hepatic
Bioavailability: ~40%
Half-life elimination: 21 hr
Excretion: Urine
Sedation: Low to moderate
Antihistamine activity: Low to moderate
Anticholinergic activity: High
Antiemetic effects: Low to moderate
