Classifications: antihistamine; h1-receptor antagonist; Therapeutic: antihistamine; h1-receptor antagonist
Pregnancy Category: C
10 mg/mL injection; 2 mg/5 mL elixir; 4 mg tablet; ingredient in many oral combination products containing a decongestant, expectorant, and/or analgesic
Antihistamine that has less sedative effect than diphenhydramine. Competes with histamine for H1-receptor sites on effector cells in the bronchi and bronchioles, thus blocking histamine-mediated responses.
Effective against upper respiratory symptoms and allergic manifestations.
Symptomatic treatment of allergic manifestations. Also used in various cough mixtures and antihistamine-decongestant cold
Hypersensitivity to antihistamines; acute asthma; pregnancy (category C), newborns.
Older adults; prostatic hypertrophy; GI obstruction; asthma; narrow-angle glaucoma; COPD, cardiovascular or renal disease;
seizure disorders; hyperthyroidism; lactation.
Route & Dosage
Adult: PO 48 mg t.i.d. or q.i.d. or 812 mg of sustained release b.i.d. or t.i.d. SC/IM/IV 520 mg q612h (max: 40 mg/24 h)
Geriatric: PO 4 mg 12 times/d
Child: PO >6 y, 24 mg t.i.d. or q.i.d. or 812 mg of sustained release b.i.d. (max: 12 mg/24 h); <6 y, 0.5 mg/kg in 34 divided doses
- Give with meals or a snack to prevent gastric irritation.
- Give without further dilution or diluted to a 1:10 ratio with NS.
PREPARE: Direct: Give undiluted or diluted with 10 mL D5W or NS.
ADMINISTER: Direct: Give IV push slowly over 1 min to a recumbent patient.
INCOMPATIBILITIES Solution/additive: Radio-contrast media (diatrizoate, iothalamate), insulin, pentobarbital.
- Store in tightly covered container at 15°30° C (59°86° F) unless otherwise directed. Elixir
and parenteral form should be protected from light. Avoid freezing.
Adverse Effects (≥1%) Body as a Whole:
Hypersensitivity reaction (urticaria, increased sweating, agranulocytosis
). CNS: Sedation,
drowsiness, dizziness, headache, disturbed coordination. GI:
Dry mouth, throat, and nose, stomach upset, constipation
. Special Senses:
Ringing or buzzing in ears. Skin:
Diagnostic Test Interference
May cause false-negative allergy skin tests.
and other cns depressants
add to sedation.
39 h. Duration:
Up to 48 h. Distribution:
Crosses placenta. Elimination:
40% in urine within 72 h; 2% in feces. Half-Life:
Assessment & Drug Effects
- Drowsiness, sweating, transient hypotension, and syncope may follow IV administration; reaction to drug should be evaluated.
Keep physician informed.
- Note: Older adults tend to be particularly susceptible to drug's sedative effect, dizziness, and hypotension. Most symptoms respond
to reduction in dosage.
- Lab tests: Periodic CBC in patients receiving long-term therapy.
Patient & Family Education
- Acute hypersensitivity reaction can occur within minutes to hours after drug ingestion. Reaction is manifested by high fever,
chills, and possible development of ulcerations of mouth and throat, pneumonia, and prostration. Patient should seek medical
- Follow diligent mouth care. Sugarless gum, lemon drops, or frequent rinses with warm water may relieve dry mouth.
- Do not drive a car or perform other potentially hazardous activities until response to drug is known.
- Do not take alcoholic beverages or other CNS depressants (e.g., tranquilizers, sedatives, pain or sleeping medicines) without