Dexchlor, Mylaramine
Classifications: antihistamine; h1-receptor antagonist;
Therapeutic: antihistamine
; h1-receptor antagonist
Prototype: Diphenhydramine
Pregnancy Category: B


2 mg tablets; 4 mg, 6 mg sustained release tablets; 2 mg/5 mL syrup


H1-receptor antagonist that competes for H1-receptor sites on cells, thus blocking histamine release.

Therapeutic Effect

Has high antihistamine effects and moderate anticholinergic effects.


Perennial and seasonal allergic rhinitis, other manifestations of allergy, and vasomotor rhinitis. Also as adjunct to epinephrine in treatment of anaphylactic reactions.


Hypersensitivity to antihistamines of similar class; closed-angle glaucoma; acute asthmatic attack, lower respiratory tract symptoms, newborns, premature infants, children <2 y.

Cautious Use

Increased intraocular pressure; prostatic hypertrophy; hyperthyroidism; asthma, COPD; renal, hepatic, and cardiovascular disease; serious GI disorders; older adults; pregnancy (category B), lactation.

Route & Dosage

Allergic Rhinitis
Adult: PO 2 mg q4–6h or 4–6 mg of repeat-action tablets h.s. or q8–10h during the day
Child: PO 2–5 y, 0.5 mg q4–6h (max: 3 mg/24 h); 6–11 y, 1 mg  q4–6h (max: 6 mg/24 h) or 4 mg of repeat-action tablets h.s.


  • Ensure that sustained release form of drug is not chewed or crushed. It must be swallowed whole.
  • Give regular tablet whole or crushed and taken with fluid or mixed with food.
  • Give medication with food, water, or milk to lessen GI distress.
  • Store at 15°–30° C (59°–86° F) unless otherwise directed.

Adverse Effects (≥1%)

CNS: Drowsiness, dizziness, weakness, headache, excitation, neuritis, disturbed coordination, insomnia, euphoria, paresthesias. Special Senses: Vertigo, tinnitus, acute labyrinthitis; blurred vision. CV: Palpitations, tachycardia, hypotension, extrasystoles. GI: Nausea, vomiting, anorexia, dry mouth, constipation, diarrhea. Urogenital: Difficulty in urinating, urinary retention, urinary frequency, early menses. Hematologic: Agranulocytosis (rare), hemolytic or hypoplastic anemia. Skin: Skin eruptions, photosensitivity.

Diagnostic Test Interference

In common with other antihistamines, dexchlorpheniramine may interfere with skin tests for allergy; discontinue dexchlorpheniramine at least 72 h before tests.


Drug: Alcohol and other cns depressants, mao inhibitors compound CNS depression.


Absorption: Readily from GI tract. Onset: 15–30 min. Peak: 3 h. Distribution: Small amounts into breast milk. Metabolism: In liver. Elimination: In urine within 24 h.

Nursing Implications

Assessment & Drug Effects

  • Supervise ambulation and take safety precautions, especially with older adult patients.
  • Monitor I&O and assess for difficulty voiding (e.g., frequency or retention).

Patient & Family Education

  • Swallow timed or sustained release tablet whole. Do not break, crush, or chew.
  • Do not drive or engage in other potentially hazardous activities until reaction to drug is known.
  • Ask physician about the use of alcohol, tranquilizers, sedatives, or other CNS depressants because the effects of dexchlorpheniramine will be additive.
  • Discontinue dexchlorpheniramine about 4 d before skin tests for allergies, since it can make test results inaccurate.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2023 Last Updated On: 01/30/2023 (0)
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