PBZ-SR, Pelamine, Pyribenzamine 
Classifications: antihistamine; h1-receptor antagonist;
Therapeutic: antihistamine
; h1-receptor antagonist
Prototype: Diphenhydramine
Pregnancy Category: B


25 mg, 50 mg tablets; 100 mg sustained release tablets


Antihistamine with mild CNS depressant effects. Antagonizes histamine action (i.e., increased capillary permeability, edema formation, itching, and constriction of respiratory, GI, and vascular smooth muscle).

Therapeutic Effect

Has antihistamine, antitussive, anticholinergic, and local anesthetic action.


To relieve symptoms of various allergic conditions, to ameliorate reactions to blood or plasma, and in anaphylaxis as adjunct to epinephrine and other standard measures after acute symptoms have been controlled. Also to provide oral mucous membrane analgesia in young children with herpetic gingiva-stomatitis.


Narrow-angle glaucoma; symptomatic prostatic hypertrophy; bladder neck obstruction; GI obstruction or stenosis; lower respiratory tract symptoms, including asthma; within 14 d of MAO inhibitor therapy. Safe use in neonates and premature infants is not established.

Cautious Use

History of asthma; convulsive disorders; increased intraocular pressure; hyperthyroidism; cardiovascular disease; hypertension; diabetes mellitus; pregnancy (category B), lactation.

Route & Dosage

Allergic Conditions
Adult: PO 25–50 mg q4–6h or 100 mg sustained release q8–12h (max: 600 mg/d)
Child: PO 5 mg/kg/d in 4–6 divided doses (max: 300 mg/d)


  • Give with or immediately after meals or food or with a glass of milk or water to lessen GI adverse effects.
  • Do not use sustained release formulation (100 mg) with children of any age.
  • Do not crush, break, or chew sustained release tablets. These must be swallowed whole.
  • Store in tight, light-resistant containers.

Adverse Effects (≥1%)

Respiratory: Thickened bronchial secretions, wheezing, sensation of chest tightness. Special Senses: Blurred vision, diplopia. Urogenital: Urinary hesitancy or retention; dysuria. CV: Palpitation, tachycardia, mild hypotension or hypertension, cardiovascular collapse. CNS: Drowsiness, dizziness, tinnitus, vertigo, fatigue, headache; disturbed coordination, tingling, tremors, euphoria, nervousness, restlessness, insomnia, hallucinations, excitement. GI: Epigastric distress, anorexia, nausea, vomiting, constipation or diarrhea, dry mouth, nose, and throat. Hematologic: Leukopenia, hemolytic anemia. Skin: Skin rash, urticaria, photosensitivity. Body as a Whole: Anaphylactic shock, fever, ataxia, athetosis, convulsions, coma.


Drug: Alcohol and other cns depressants add to CNS depression; mao inhibitors may intensify anticholinergic effects.


Absorption: Readily from GI tract. Onset: 15–30 min. Peak: 2–3 h. Duration: 4–6 h (up to 8 h with sustained release). Distribution: Crosses placenta; distributed into breast milk. Metabolism: In liver. Elimination: In urine.

Nursing Implications

Assessment & Drug Effects

  • Assist older adults during ambulation; dizziness, sedation, and hypotension are more likely to occur in this age group.
  • Lab tests: Obtain periodic blood cell counts during long-term therapy with antihistamines.

Patient & Family Education

  • Void just before taking drug if urinary hesitancy is a problem.
  • Do not drive or engage in potentially hazardous activities until response to drug is known. Mild to moderate drowsiness, blurred vision, and dizziness occur in some patients.
  • Be aware that the effects of antihistamines may be augmented by concomitant use of alcohol or other CNS depressants.
  • Do not take OTC preparations without consulting physician.
  • Discontinue antihistamines within 4 d before skin testing procedure for allergy because drug may interfere with reactions and obscure test results.

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: 10/03/2022 (0)
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