diphenhydrAMINE

General

**BEERS Drug**

(oral, parenteral)

Pronunciation:
dye-fen-hye-dra-meen


Trade Name(s)

  • Aller-Aide Canadian Tradename
  • Allerdryl Canadian Tradename
  • Allergy Formula Canadian Tradename
  • AllerMax
  • Allernix Canadian Tradename
  • Banophen
  • Benadryl Dye-Free Alergy
  • Benadryl Allergy
  • Benadryl
  • Benylin Canadian Tradename
  • Calmex Canadian Tradename
  • Compoz
  • Compoz Nighttime Sleep Aid
  • Dimetane Allergy Canadian Tradename
  • Diphen AF
  • Diphen Cough
  • Diphenhist Canadian Tradename
  • Dormex Canadian Tradename
  • Dormiphen Canadian Tradename
  • Genahist
  • 40 Winks
  • Hyrexin-50
  • Insomnal Canadian Tradename
  • Maximum Strength Nytol
  • Maximum Strength Sleepinal
  • Midol PM
  • Miles Nervine
  • Nadryl Canadian Tradename
  • Nighttime Sleep Aid
  • Nytol
  • Scot-Tussin Allergy DM
  • Siladril
  • Silphen
  • Sleep-Eze 3
  • Sleepwell 2-night
  • Sominex
  • Snooze Fast
  • Sominex
  • Tusstat
  • Twilite
  • Unisom Nighttime Sleep-Aid

Ther. Class.
allergy, cold and cough remedies
antihistamines
antitussives

Indications

  • Relief of allergic symptoms caused by histamine release including:

    • Anaphylaxis,
    • Seasonal and perennial allergic rhinitis,
    • Allergic dermatoses.
  • Parkinson's disease and dystonic reactions from medications.
  • Mild nighttime sedation.
  • Prevention of motion sickness.
  • Antitussive (syrup only).

Action

  • Antagonizes the effects of histamine at H1 -receptor sites; does not bind to or inactivate histamine.
  • Significant CNS depressant and anticholinergic properties.

Therapeutic Effect(s):

  • Decreased symptoms of histamine excess (sneezing, rhinorrhea, nasal and ocular pruritus, ocular tearing and redness, urticaria).
  • Relief of acute dystonic reactions.
  • Prevention of motion sickness.
  • Suppression of cough.

Pharmacokinetics

Absorption: Well absorbed after oral or IM administration but 40–60% of an oral dose reaches systemic circulation due to first-pass metabolism.

Distribution: Widely distributed. Crosses the placenta; enters breast milk.

Metabolism and Excretion: 95% metabolized by the liver.

Half-life: 2.4–7 hr.

TIME/ACTION PROFILE (antihistaminic effects)

ROUTEONSETPEAKDURATION
PO15–60 min2–4 hr4–8 hr
IM20–30 min2–4 hr4–8 hr
IVrapidunknown4–8 hr

Contraindication/Precautions

Contraindicated in:

  • Hypersensitivity;
  • Acute attacks of asthma;
  • Lactation;
  • Known alcohol intolerance (some liquid products).

Use Cautiously in:

  • Severe liver disease;
  • Angle-closure glaucoma;
  • Seizure disorders;
  • Prostatic hyperplasia;
  • Peptic ulcer;
  • May cause paradoxical excitation in young children;
  • Hyperthyroidism;
  • OB:  Safety not established;
  • Geri:  Appears on  Beers list. Geriatric patients are more susceptible to adverse drug reactions and anticholinergic effects (delirium, acute confusion, dizziness, dry mouth, blurred vision, urinary retention, constipation, tachycardia); dose ↓ or nonanticholinergic antihistamine recommended.

Adverse Reactions/Side Effects

EENT: blurred vision, tinnitus

CV: hypotension, palpitations

GI: anorexia, dry mouth, constipation, nausea

GU: dysuria, frequency, urinary retention

Derm: photosensitivity

Neuro: drowsiness, dizziness, headache, paradoxical excitation (increased in children)

Resp: chest tightness, thickened bronchial secretions, wheezing

Local: pain at IM site

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

Drug-Natural Products:

Concomitant use of  kava-kava,  valerian, or  chamomile  can ↑ CNS depression.

Route/Dosage

PO (Adults and Children >12 yr): Antihistaminic/antiemetic/antivertiginic– 25–50 mg every 4–6 hr, not to exceed 300 mg/day.   Antitussive– 25 mg every 4 hr as needed, not to exceed 150 mg/day.   Antidyskinetic– 25–50 mg every 4 hr (not to exceed 400 mg/day).   Sedative/hypnotic– 50 mg 20–30 min before bedtime.

PO (Children  6–12 yr): Antihistaminic/antiemetic/antivertiginic– 12.5–25 mg every 4–6 hr (not to exceed 150 mg/day).  Antidyskinetic– 1–1.5 mg/kg every 6–8 hr as needed (not to exceed 300 mg/day).  Antitussive– 12.5 mg every 4 hr (not to exceed 75 mg/day).   Sedative/hypnotic– 1 mg/kg/dose 20–30 min before bedtime (not to exceed 50 mg).

PO (Children  2–6 yr): Antihistaminic/antiemetic/antivertiginic– 6.25–12.5 mg every 4–6 hr (not to exceed 37.5 mg/day).  Antidyskinetic– 1–1.5 mg/kg every 4–6 hr as needed (not to exceed 300 mg/day).  Antitussive– 6.25 mg every 4 hr (not to exceed 37.5 mg/24 hr).   Sedative/hypnotic– 1 mg/kg/dose 20–30 min before bedtime (not to exceed 50 mg).

IM IV (Adults): 25–50 mg every 4 hr as needed (may need up to 100-mg dose, not to exceed 400 mg/day).

IM IV Children: 1.25 mg/kg (37.5 mg/m2 ) 4 times daily (not to exceed 300 mg/day).

Topical (Adults and Children ≥2 yr): Apply to affected area up to 3–4 times daily.

Availability (generic available)

Capsules: 25 mgRx, OTC, 50 mgRx, OTC

Tablets: 12.5 mgRx, OTC Canadian Tradename, 25 mgRx, OTC, 50 mgRx, OTC

Chewable tablets (grape flavor): 25 mgRx, OTC

Orally disintegrating strips (cherry and grape flavor): 12.5 mgRx, OTC, 25 mgOTC

Orally disintegrating tablets: 12.5 mgOTC, 25 mgOTC, 50 mgRx, OTC

Elixir (cherry and other flavors): 12.5 mg/5 mLRx, OTC

Syrup (cherry and raspberry flavor): 6.25 mg/5 mLRx, OTC Canadian Tradename, 12.5 mg/5 mLRx, OTC

Cream: 1%Rx, OTC, 2%Rx, OTC

Topical gel: 2%OTC

Topical spray: 2%OTC

Topical stick: 2%OTC

Injection: 50 mg/mL

In Combination with: analgesics, decongestants, and expectorants, in OTC pain, sleep, cough, and cold preparations. See combination drugs.

Assessment

  • Diphenhydramine has multiple uses. Determine why the medication was ordered and assess symptoms that apply to the individual patient. Geri:  Appears in the  Beers list.  May cause sedation and confusion due to increased sensitivity to anticholinergic effects. Monitor carefully, assess for confusion, delirium, other anticholinergic side effects and fall risk. Institute measures to prevent falls.
  • Prevention and Treatment of Anaphylaxis: Assess for urticaria and for patency of airway.
  • Allergic Rhinitis: Assess degree of nasal stuffiness, rhinorrhea, and sneezing.
  • Parkinsonism and Extrapyramidal Reactions: Assess movement disorder before and after administration.
  • Insomnia: Assess sleep patterns.
  • Motion Sickness: Assess nausea, vomiting, bowel sounds, and abdominal pain.
  • Cough Suppressant: Assess frequency and nature of cough, lung sounds, and amount and type of sputum produced. Unless contraindicated, maintain fluid intake of 1500–2000 mL daily to decrease viscosity of bronchial secretions.
  • Pruritus: Assess degree of itching, skin rash, and inflammation.

Lab Test Considerations:

May ↓ skin response to allergy tests. Discontinue 4 days before skin testing.

Potential Diagnoses

Implementation

  • Do not confuse Benadryl with benazepril. Do not confuse diphenhydramine with dimenhydrinate.

    • When used for insomnia, administer 20 min before bedtime and schedule activities to minimize interruption of sleep.
    • When used for prophylaxis of motion sickness, administer at least 30 min and preferably 1–2 hr before exposure to conditions that may precipitate motion sickness.
  • PO 

    Administer with meals or milk to minimize GI irritation. Capsule may be emptied and contents taken with water or food.

    • Orally disintegrating tablets and strips should be left in the package until use. Remove from the blister pouch. Do not push tablet through the blister; peel open the blister pack with dry hands and place tablet on tongue. Tablet will dissolve rapidly and be swallowed with saliva. No liquid is needed to take the orally disintegrating tablet.
  • IM Administer 50 mg/mL into well-developed muscle. Avoid subcut injections.
  • Topical Apply a thin coat and rub gently until absorbed. Only for topical use; avoid ingestion.

IV Administration

  • IV Push:   Diluent:  May be further diluted in 0.9% NaCl, 0.45% NaCl, D5W, D10W, dextrose/saline combinations, Ringer's solution, LR, and dextrose/Ringer's combinations. Concentration: 25 mg/mL.
  • Rate: Infuse at a rate not to exceed 25 mg/min.
  • Y-Site Compatibility:
    • acetaminophen
    • aldesleukin
    • alemtuzumab
    • MORE...
      • alfentanil
      • amifostine
      • amikacin
      • aminocaproic acid
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      • amphotericin B liposome
      • amsacrine
      • anidulafungin
      • argatroban
      • ascorbic acid
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      • azithromycin
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      • bleomycin
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      • butorphanol
      • calcium chloride
      • calcium gluconate
      • carboplatin
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      • caspofungin
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      • ciprofloxacin
      • cisatracurium
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      • cyanocobalamin
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      • digoxin
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      • doxorubicin
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      • ertapenem
      • erythromycin
      • esmolol
      • etoposide
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      • famotidine
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      • fentanyl
      • filgrastim
      • fluconazole
      • fludarabine
      • folic acid
      • fosphenytoin
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      • granisetron
      • hetastarch
      • hydromorphone
      • idarubicin
      • ifosfamide
      • imipenem/cilastatin
      • irinotecan
      • isoproterenol
      • ketamine
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      • lidocaine
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      • magnesium sulfate
      • mannitol
      • melphalan
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      • meropenem
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      • metoclopramide
      • metoprolol
      • metronidazole
      • midazolam
      • mitomycin
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      • morphine
      • moxifloxacin
      • multiple vitamins
      • mycophenolate
      • nalbuphine
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      • nicardipine
      • nitroglycerin
      • norepinephrine
      • octreotide
      • ondansetron
      • oxaliplatin
      • oxytocin
      • paclitaxel
      • palonosetron
      • pamidronate
      • papaverine
      • pemetrexed
      • penicillin G
      • pentamidine
      • phentolamine
      • phenylephrine
      • phytonadione
      • piperacillin/tazobactam
      • potassium acetate
      • potassium chloride
      • procainamide
      • prochlorperazine
      • promethazine
      • propofol
      • propranolol
      • protamine
      • pyridoxime
      • quinipristin/dalfopristin
      • remifentanil
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      • sodium acetate
      • succinylcholine
      • sufentanil
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      • theophylline
      • thiamine
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      • verapamil
      • vinblastine
      • vincristine
      • vinorelbine
      • vitamin B complex with C
      • voriconazole
      • zoledronic acid
  • Y-Site Incompatibility:
    • allopurinol
    • aminophylline
    • amphotericin B deoxycholate
    • MORE...
      • ampicillin
      • azathioprine
      • cefazolin
      • cefepime
      • cefotaxime
      • cefotetan
      • cefoxitin
      • ceftazidime
      • ceftriaxone
      • cefuroxime
      • chloramphenicol
      • dantrolene
      • dexamethasone
      • diazepam
      • diazoxide
      • fluorouracil
      • foscarnet
      • furosemide
      • ganciclovir
      • indomethacin
      • insulin
      • ketorolac
      • methylprednisolone
      • milrinone
      • nitroprusside
      • oxacillin
      • pantoprazole
      • pentobarbital
      • phenobarbital
      • phenytoin
      • sodium bicarbonate
      • trimethoprim/sulfamethoxazole

Patient/Family Teaching

Instruct patient to take medication as directed; do not exceed recommended amount. Caution patient not to use oral OTC diphenhydramine products with any other product containing diphenhydramine, including products used topically.

  • May cause drowsiness. Caution patient to avoid driving or other activities requiring alertness until response to drug is known.
  • May cause dry mouth. Inform patient that frequent oral rinses, good oral hygiene, and sugarless gum or candy may minimize this effect. Notify health care professional if dry mouth persists for more than 2 wk.
  • Teach sleep hygiene techniques (dark room, quiet, bedtime ritual, limit daytime napping, avoidance of nicotine and caffeine) to patients taking diphenhydramine to aid sleep.
  • Advise patient to use sunscreen and protective clothing to prevent photosensitivity reactions.
  • Caution patient to avoid use of alcohol and other CNS depressants concurrently with this medication.
  • Pedi:  Can cause excitation in children. Caution parents or caregivers about proper dose calculation; overdose, especially in infants and children, can cause hallucinations, seizures, or death. Caution parents to avoid OTC cough and cold products while breast feeding or to children <4 yr.
  • Geri:  Instruct older adults to avoid OTC products that contain diphenhydramine due to increased sensitivity to anticholinergic effects and potential for adverse reactions related to these effects.
  • Advise patients taking diphenhydramine in OTC preparations to notify health care professional if symptoms worsen or persist for more than 7 days.

Evaluation/Desired Outcomes

  • Prevention of, or decreased urticaria in, anaphylaxis or other allergic reactions.
  • Decreased dyskinesia in parkinsonism and extrapyramidal reactions.
  • Sedation when used as a sedative/hypnotic.
  • Prevention of or decrease in nausea and vomiting caused by motion sickness.
  • Decrease in frequency and intensity of cough without eliminating cough reflex.
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