clemastine

Absorption: Well absorbed following oral administration.

Distribution: Widely distributed to tissues.

Metabolism/Excretion: Extensively metabolized by the liver.

Half-Life: 21 hr.

Time/Action Profile ⬆ ⬇

(antihistaminic effects)

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

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Angle-closure glaucoma;
Known alcohol intolerance (liquid form);
Lactation: Lactation.

Use Cautiously in:

Acute asthma attacks;
Liver disease;
Prostatic hyperplasia;
Hyperthyroidism;
Hypertension;
OB: 2nd-generation antihistamines are preferred in pregnancy;
Pedi: Children <6 yr (safety and effectiveness not established);
Geri: Older adults are more susceptible to adverse reactions.

Adv. Reactions/Side Effects ⬆ ⬇

CV: hypertension, arrhythmias, hypotension, palpitations, tachycardia

Derm: rash

EENT: blurred vision

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

GU: urinary retention

Neuro: drowsiness, confusion, dizziness, paradoxical excitation (children)

Resp: thick mucus

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:

Kava-kava, valerian, skullcap, chamomile, or hops can ↑ risk of 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 ↑ 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 ⬆ ⬇

(Generic available)

Tablets: 2.68 mg (2 mg base)
Syrupcitrus flavor: 0.67 mg/5 mL (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 during therapy.
Assess lung sounds and character of bronchial secretions. Maintain fluid intake of 1500–2000 mL/day to ↓ viscosity of secretions.

Lab Test Considerations:

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

Implementation ⬆ ⬇

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

Patient/Family Teaching ⬆ ⬇

Explain purpose and side effects of medication. Advise patient to read Patient Information before starting therapy.
Instruct patient not to take more than recommended amount. Take missed doses as soon as possible unless almost time for next dose.
Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult health care professional before taking other medications.
Caution patient to avoid using alcohol or other CNS depressants, including opioids, concurrently with this drug.
May cause drowsiness. Caution patient to avoid driving or other activities requiring alertness until response to drug is known.
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.
Caution patient of risk for orthostatic hypotension and to change positions slowly, especially older adults.
Instruct patient to notify health care professional of difficulty with urination, change in vision, confusion, severe dry mucous membranes, or dizziness.
Advise parent or caretaker of risk for paradoxical reaction in children and to notify health care professional if the child has difficulty sleeping, becomes unusually excited or irritable, or develops shortness of breath or facial flushing.
Advise women of reproductive potential to notify health care professional if pregnancy is planned or suspected and to avoid use during breastfeeding.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇