clemastine

General

Pronunciation
KLEM-as-teen [Pronunciation]

Trade Name(s)

• Dayhist Allergy

• Tavist Allergy

Pregnancy Category
Category B

Ther. class.
allergy, cold and cough remedies
antihistamines

Indications

Relief of allergic symptoms caused by histamine release including:

» Allergic rhinitis,

» Urticaria.

Action

Antagonizes the effects of histamine at H-receptor sites; does not bind to or inactivate histamine.

Therapeutic Effect(s):
Decreased symptoms of histamine excess (sneezing, rhinorrhea, nasal and ocular pruritus, ocular tearing, and redness).

Pharmacokinetics

Absorption: Well absorbed following oral administration.

Distribution: Enters breast milk in high concentrations.

Metabolism and Excretion: Extensively metabolized by the liver.

Half-life: Unknown.

TIME/ACTION PROFILE (antihistaminic effects)

ROUTE	ONSET	PEAK	DURATION
PO	15–60 min	1–2 hr	8–16 hr

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity;

• Angle-closure glaucoma;

• Lactation (avoid use);

• Known alcohol intolerance (liquid form).

Use Cautiously in:

• Acute asthma attacks;

• Liver disease;

• Prostatic hyperplasia;

• Hyperthyroidism;

• Hypertension;

• Geriatric patients (more susceptible to adverse reactions);

• Pregnancy or children <6 yr (safety not established).

Adverse Reactions/Side Effects

CNS: drowsiness, confusion, dizziness, paradoxical excitation (children).

EENT: blurred vision.

CV: hypertension, arrhythmias, hypotension, palpitations, tachycardia.

GI: dry mouth, constipation, nausea, obstruction, vomiting.

GU: urinary retention.

Derm: rash.

Resp: thick mucus.

*CAPITALS indicates life-threatening.
*italic indicates most frequent.

Interactions

Drug-Drug

• Additive CNS depression with other CNS depressants , including alcohol , opioid analgesics , and sedative/hypnotics .

• May antagonize effects of cholinergic agonists (e.g. donepezil ).

Drug-Natural Products
Concomitant use of kava-kava , valerian , skullcap , chamomile , or hops can increase CNS depression.

Route/Dosage

• PO (Adults): OTC labeling—1.34 mg (1 mg base) twice daily. Rx labeling—1.34 mg (1 mg base) twice daily; may increase up to 2.68 mg (2 mg base) 3 times daily..

• PO (Children 6–12 yr): 0.67–1.34 mg (0.5–1 mg base) twice daily. (not to exceed 4.02 mg/day (3 mg/day base)..

Availability

• Tablets: 1 mg^OTC[canada], 1.34 mg (1 mg base)^OTC, 2.68 mg (2 mg base)

• Syrup (citrus flavor): 0.67 mg/5 mLRx (0.67 mg clemastine fumarate = 0.5 mg base) (contains 5.5% alcohol)

Assessment

• Assess allergy symptoms (rhinitis, conjunctivitis, hives, urticaria) prior to and periodically throughout therapy.

• Assess lung sounds and character of bronchial secretions. Maintain fluid intake of 1500–2000 mL/day to decrease viscosity of secretions.

Lab Test Considerations

• May cause false-negative reactions on allergy skin tests; discontinue 3 days prior to testing.

Toxicity and Overdose

• Symptoms of toxicity in children include excitement, hyperreflexia, hallucinations, tremors, ataxia, fever, seizures, fixed dilated pupils, dry mouth, and facial flushing. The dose that causes seizures approximates the lethal dose. Adults are more likely to experience severe drowsiness.

Potential Nursing Diagnoses

• Ineffective airway clearance (Indications)

• Risk for injury (Adverse Reaction)

Implementation

PO: Administer with food or milk to decrease GI irritation.

Patient/Family Teaching

• Instruct patient to take medication as directed. Do not take more than recommended amount. Missed doses should be taken as soon as possible unless almost time for next dose. Do not double doses.

• May cause drowsiness. Caution patient to avoid driving or other activities requiring alertness until response to drug is known.

• Caution patient to avoid using alcohol or other CNS depressants concurrently with this drug.

• Advise patient that good oral hygiene, frequent rinsing of mouth with water, and sugarless gum or candy may help relieve dry mouth. Patient should notify dentist if dry mouth persists for >2 wk.

• Geriatric patients are at risk for orthostatic hypotension. Advise patient to change positions slowly.

• Instruct patient to contact health care professional if symptoms persist or if difficulty with urination; changes in vision; confusion; severe dry mouth, nose, and throat; or dizziness occurs. May be more common in geriatric patients. Parents should notify health care professional if their child has difficulty sleeping, becomes unusually excited or irritable, or develops shortness of breath or facial flushing.

Evaluation/Desired Outcomes

Decrease in allergic symptoms.