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diphenhydramine (Benadryl, Alledryl, Allergival)

Tradename: Benadryl. (diphenhydramine hydrochloride) Indications: - allergies - allergic conjunctivitis, allergic rhinitis - pruritus, urticaria - atopy - anaphylaxis - cold symptoms - nasal congestion, rhinorrhea, sneezing - cough - nausea/vomiting - motion sickness, vertigo - insomnia - extrapyramidal signs [6] Dosage: 1) antihistamine: 25-50 mg PO/IM/IV every 6 hours 2) antitussive: 25 mg PO every 4 hours PRN 3) nausea/vomiting: 25-50 mg PO/IM/IV every 6 hours 4) motion sickness: 25-50 mg PO/IM/IV every 6 hours 5) sleep aid: 50-100 mg PO QHS 6) extrapyramidal signs: 25-50 mg PO TID-QID Tabs: 25 & 50 mg Children: 5 mg/kg/day. Elixir 12.5 mg/5 mL. Pharmacokinetics: 1) oral dose undergoes 1st pass metabolism with 40-60% of drug reaching systemic circulation 2) sedative effects occur within 1-3 hours after single dose 3) 1/2life is 3-9 hours in healthy adults 4) metabolized by the liver 5) eliminated in the urine Adverse effects: (anti-cholinergic effects) 1) dry mouth 2) blurred vision 3) dizziness (rare) 4) sedation 5) urinary retention 6) constipation 7) seizures (rare) [4] 8) cognitive decline, delirium in the elderly Overdose: 1) hallucinations 2) sleepiness 3) difficulty walking 4) dizziness 5) inability to speak 6) unconsciousness [5] 7) seizures, coma, death, heart problems [7] Drug interactions: 1) other CNS depressants 2) MAO inhibitors intensify anti-cholinergic effects Laboratory: 1) specimen: serum 2) methods: GLC Mechanism of action: 1) H1 receptor antagonist 2) anticholinergic agent 3) antiemetic agent a) acts on vomiting center b) anti-motion sickness properties 4) anesthetic

Interactions

drug interactions drug adverse effects (more general classes)

Related

chemoreceptor trigger zone (CTZ) parkinsonism

Specific

bromodiphenhydramine

General

antipruritic agent anti-emetic ethanolamine H1 receptor antagonist (antihistamine) parasympatholytic (anticholinergic, antimuscarinic agent) sedative/hypnotic (tranquilizer)

Properties

MISC-INFO: elimination route LIVER KIDNEY 1/2life 5-8 HOURS therapeutic-range 9-112 NG/ML toxic-range >0.5 UG/ML >1.96 UMOL/L pregnancy-category B - <1st trimester> safety in lactation -

Database Correlations

PUBCHEM correlations

References

  1. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
  2. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
  3. Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995
  4. Medications Can Cause Seizures Prescriber's Letter 10(3):16 2003 Detail-Document#: 190320 (subscription needed) http://www.prescribersletter.com
  5. FDA Medwatch Benadryl Extra Strength Itch Stopping Gel: Packaging Changes to Reduce Use Errors http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm211792.htm
  6. Deprecated Reference
  7. FDA Medwatch. Sept 24, 2020 Benadryl (diphenhydramine): Drug Safety Communication - Serious Problems with High Doses of the Allergy Medicine. https://www.fda.gov/safety/medical-product-safety-information/benadryl-diphenhydramine-drug-safety-communication-serious-problems-high-doses-allergy-medicine

Component-of

acetaminophen/aspirin/diphenhydramine acetaminophen/chlorpheniramine/diphenhydramine/phenylephrine acetaminophen/chlorpheniramine/diphenhydramine/pseudoephedrine acetaminophen/citrate/diphenhydramine acetaminophen/dextromethorphan/diphenhydramine acetaminophen/dextromethorphan/diphenhydramine/guaifenesin acetaminophen/dextromethorphan/diphenhydramine/guaifenesin/phenylephrine acetaminophen/dextromethorphan/diphenhydramine/phenylephrine acetaminophen/dextromethorphan/diphenhydramine/pseudoephedrine acetaminophen/diphenhydramine acetaminophen/diphenhydramine/doxylamine acetaminophen/diphenhydramine/guaifenesin/phenylephrine acetaminophen/diphenhydramine/phenylephrine acetaminophen/diphenhydramine/phenylephrine/pseudoephedrine acetaminophen/diphenhydramine/pseudoephedrine acetic acid/diphenhydramine allantoin/diphenhydramine aluminum hydroxide/diphenhydramine/lidocaine/magnesium hydroxide/simethicone aspirin/citrate/diphenhydramine/nov protein aspirin/diphenhydramine Benadryl/Carafate/Mylanta benzethonium/cortisol/diphenhydramine benzethonium/diphenhydramine/zinc acetate benzyl alcohol/calamine/diphenhydramine brompheniramine/dextromethorphan/diphenhydramine brompheniramine/diphenhydramine brompheniramine/diphenhydramine/phenylephrine calamine/diphenhydramine carbetapentane/diphenhydramine carbetapentane/diphenhydramine/phenylephrine citrate/diphenhydramine/ibuprofen citrate/diphenhydramine/pseudoephedrine clemastine/diphenhydramine/pseudoephedrine codeine/diphenhydramine/phenylephrine codeine/diphenhydramine/phenylephrine/phosphate cortisol/diphenhydramine cortisol/diphenhydramine/nystatin cortisol/diphenhydramine/nystatin/tetracycline cortisol/diphenhydramine/pramoxine dextromethorphan/diphenhydramine/guaifenesin dextromethorphan/diphenhydramine/guaifenesin/phenylephrine dextromethorphan/diphenhydramine/phenylephrine dimenhydrinate (Dramamine) diphenhydramine/guaifenesin diphenhydramine/guaifenesin/phenylephrine diphenhydramine/huntingtin/hydrocodone/phenylephrine diphenhydramine/hydrocodone/phenylephrine diphenhydramine/ibuprofen (Advil PM) diphenhydramine/lidocaine/nystatin diphenhydramine/magnesium salicylate diphenhydramine/menthol diphenhydramine/naproxen diphenhydramine/phenol diphenhydramine/phenylephrine diphenhydramine/phenylephrine/pseudoephedrine diphenhydramine/pramoxine diphenhydramine/pseudoephedrine diphenhydramine/salicylate diphenhydramine/tripelennamine diphenhydramine/zinc acetate diphenhydramine/zinc/zinc acetate intravenous anti-emetic combination magic mouthwash suppository anti-emetic combination (BRD)