Aller-Chlor, Chlo-Amine, Chlor-Trimeton, Chlor-Tripolon , Novopheniram , Phenetron, Telachlor, Teldrin, Trymegan
Classifications: antihistamine (h1-receptor antagonist);
Therapeutic: antihistamine
; h1-receptor antagonist
Prototype: Diphenhydramine
Pregnancy Category: B first and second trimester; D third trimester


2 mg, 4 mg tablets; 8 mg, 12 mg sustained-release tablets; 2 mg/5 mL syrup


Antihistamine that competes with histamine for H1-receptor sites on effector cells; thus it prevents histamine action that promotes capillary permeability and edema formation and constrictive action on respiratory, gastrointestinal, and vascular smooth muscles. Produces less drowsiness than other H1-histamine antagonists.

Therapeutic Effect

Has effective antihistamine reaction resulting in decreasing allergic symptomatology.


Symptomatic relief of various uncomplicated allergic conditions; to prevent transfusion and drug reactions in susceptible patients, and as adjunct to epinephrine and other standard measures in anaphylactic reactions.


Hypersensitivity to antihistamines of similar structure; lower respiratory tract symptoms, narrow-angle glaucoma, obstructive prostatic hypertrophy or other bladder neck obstruction, GI obstruction or stenosis; pregnancy (category B in first and second trimester and category D in third trimester), premature and newborn infants; during or within 14 d of MAO INHIBITOR therapy.

Cautious Use

Convulsive disorders, increased intraocular pressure, hyperthyroidism, cardiovascular disease, hepatic disease; BPH; GI obstruction; hypertension, diabetes mellitus, history of bronchial asthma, COPD, older adult patients, patients with G6PD deficiency, lactation.

Route & Dosage

Symptomatic Allergy Relief
Adult: PO 2–4 mg t.i.d. or q.i.d. or 8–12 mg b.i.d. or t.i.d. (max: 24 mg/d)
Geriatric: PO 4 mg q.d. or b.i.d. or 8 mg sustained-release h.s.
Child: PO 6–12 y, 2 mg q4–6h (max: 12 mg/d); 2–6 y, 1 mg q4–6h


  • Give on an empty stomach for fastest response.
  • Sustained-release tablets should be swallowed whole and not crushed or chewed.
  • Ensure that chewable tablets are chewed or crushed before being swallowed with a liquid.

Adverse Effects (≥1%)

Body as a Whole: Sensation of chest tightness. CV: Palpitation, tachycardia, mild hypotension or hypertension. GI: Epigastric distress, anorexia, nausea, vomiting, constipation, or diarrhea. CNS: Drowsiness, sedation, headache, dizziness, vertigo, fatigue, disturbed coordination, tremors, euphoria, nervousness, restlessness, insomnia. Special Senses: Dryness of mouth, nose, and throat, tinnitus, vertigo, acute labyrinthitis, thickened bronchial secretions, blurred vision, diplopia. Urogenital: Urinary frequency or retention, dysuria.

Diagnostic Test Interference

Antihistamines should be discontinued 4 d before skin testing procedures for allergy because they may obscure otherwise positive reactions.


Drug: Alcohol (ethanol) and other cns depressants produce additive sedation and CNS depression.


Absorption: Well absorbed from GI tract; about 45% of dose reaches systemic circulation intact. Onset: Within 6 h. Peak: 2–6 h. Distribution: Highest concentrations in lung, heart, kidney, brain, small intestine, and spleen. Metabolism: By CYP3A4. Half-Life: 12–43 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor for CNS depression and sedation, especially when chlorpheniramine is given in combination with other CNS depressants.
  • Monitor BP in hypertensive patients since chlorpheniramine may elevate BP.

Patient & Family Education

  • Avoid driving a car and other potentially hazardous activities until drug response has been determined.
  • Avoid or minimize alcohol intake. Antihistamines have additive effects with alcohol.
  • Report any of the following: tinnitus or palpitations.
  • Consult physician before taking additional OTC drugs for allergy relief.

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

© 2006-2022 Last Updated On: 11/28/2022 (0)
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