diphenhydramine hydrochloride Nursing Considerations & Management


Generic Name : diphenhydramine hydrochloride

Brand Name:

  • Oral: Allerdryl (CAN), AllerMax Caplets, Banophen, Banophen Allergy, Benadryl Allergy, Diphen AF, Diphenhist, Diphenhist Captabs, Genahist, Siladryl, Silphen Cough
  • Oral prescription preparations: Benadryl, Tusstat
  • Parenteral preparations: Benadryl

Classification: Antihistamine, Anti-motion sickness drug, Sedative-hypnotic, Antiparkinsonian, Cough suppressant

Pregnancy Category B



  • 25–50 mg q 4–8 hr PO.
  • Motion sickness: Give full dose prophylactically 30 min before exposure to motion, and repeat before meals and at bedtime.
  • Nighttime sleep aid: 25–50 mg PO at bedtime.
  • Cough suppression: 25 mg q 4 hr PO, not to exceed 150 mg in 24 hr.


  • 10–50 mg IV or deep IM or up to 100 mg if required. Maximum daily dose is 400 mg.


  • 12.5–25 mg tid–qid PO or 5 mg/kg/day PO or 150 mg/m2 per day PO. Maximum daily dose 300 mg.
  • Motion sickness: Give full dose prophylactically 30 min before exposure to motion and repeat before meals and at bedtime.
  • Cough suppression:
    • 2–6 yr: 6.25 mg q 4 hr, not to exceed 25 mg in 24 hr.
    • 6–12 yr: 12.5 mg q 4 hr PO, not to exceed 75 mg in 24 hr.


  • 5 mg/kg/day or 150 mg/m2 per day IV or by deep IM injection. Maximum daily dose is 300 mg divided into four doses.
  • More likely to cause dizziness, sedation, syncope, toxic confusional states, and hypotension in elderly patients; use with caution.
  • Diphenhydramine blocks histamine H1-receptors on effector cells of the GI tract, blood vessels and respiratory tract. It also causes sedation and has some anticholinergic action.
  • Relief of symptoms associated with perennial and seasonal allergic rhinitis; vasomotor rhinitis; allergic conjunctivitis; mild, uncomplicated urticaria and angioedema; amelioration of allergic reactions to blood or plasma; dermatographism; adjunctive therapy in anaphylactic reactions
  • Active and prophylactic treatment of motion sickness
  • Nighttime sleep aid
  • Parkinsonism (including drug-induced parkinsonism and extrapyramidal reactions), in the elderly intolerant of more potent drugs, for milder forms of the disorder in other age groups, and in combination with centrally acting anticholinergic antiparkinsonian drugs
  • Syrup formulation: Suppression of cough due to colds or allergy
  • CNS depression, dizziness, headache, sedation; paradoxical stimulation in children; dryness of mouth, thickened respiratory secretion, blurring of vision, urinary retention; GI disturbances; blood dyscrasias.
  • Hypersensitivity ; neonates, lactation.
  • History: Allergy to any antihistamines, narrow-angle glaucoma, stenosing peptic ulcer, symptomatic prostatic hypertrophy, asthmatic attack, bladder neck obstruction, pyloroduodenal obstruction, third trimester of pregnancy, lactation
  • Physical: Skin color, lesions, texture; orientation, reflexes, affect; vision examination; P, BP; R, adventitious sounds; bowel sounds; prostate palpation; CBC with differential
  • Administer with food if GI upset occurs.
  • Administer syrup form if patient is unable to take tablets.
  • Monitor patient response, and arrange for adjustment of dosage to lowest possible effective dose.
Teaching points
  • Take as prescribed; avoid excessive dosage.
  • Take with food if GI upset occurs.
  • Avoid alcohol; serious sedation could occur.
  • These side effects may occur: Dizziness, sedation, drowsiness (use caution driving or performing tasks requiring alertness); epigastric distress, diarrhea or constipation (take drug with meals); dry mouth (use frequent mouth care, suck sugarless lozenges); thickening of bronchial secretions, dryness of nasal mucosa (use a humidifier).
  • Report difficulty breathing, hallucinations, tremors, loss of coordination, unusual bleeding or bruising, visual disturbances, irregular heartbeat.