diphenhydramine (Benadryl, Alledryl, Allergival)
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Introduction
Tradename: Benadryl. (diphenhydramine hydrochloride)
Indications
- allergies
- atopy
- anaphylaxis
- cold symptoms
- cough
- nausea/vomiting
- motion sickness, vertigo
- insomnia
- extrapyramidal signs[6]
Dosage
- antihistamine: 25-50 mg PO/IM/IV every 6 hours
- antitussive: 25 mg PO every 4 hours PRN
- nausea/vomiting: 25-50 mg PO/IM/IV every 6 hours
- motion sickness: 25-50 mg PO/IM/IV every 6 hours
- sleep aid: 50-100 mg PO QHS
- extrapyramidal signs: 25-50 mg PO TID-QID
Tabs: 25 & 50 mg
Children: 5 mg/kg/day. Elixir 12.5 mg/5 mL.
Pharmacokinetics
- oral dose undergoes 1st pass metabolism with 40-60% of drug reaching systemic circulation
- sedative effects occur within 1-3 hours after single dose
- 1/2life is 3-9 hours in healthy adults
- metabolized by the liver
- eliminated in the urine
elimination via liver
elimination via kidney
1/2life = 5-8 hours
Adverse effects
(anti-cholinergic effects)
- dry mouth
- blurred vision
- dizziness (rare)
- sedation
- urinary retention
- constipation
- seizures (rare)[4]
- cognitive decline, delirium in the elderly
- hallucinations
- sleepiness
- difficulty walking
- dizziness
- inability to speak
- unconsciousness[5]
- seizures, coma, death, heart problems[7]
- drug adverse effects of parasympatholytics
- drug adverse effects of H1 receptor antagonists
- drug adverse effects of psychotropic agents
- drug adverse effects of sedatives
Drug interactions
- other CNS depressants
- MAO inhibitors intensify anti-cholinergic effects
Laboratory
Mechanism of action
- H1 receptor antagonist
- anticholinergic agent
- antiemetic agent
- acts on vomiting center
- anti-motion sickness properties
- anesthetic
More general terms
- H1 receptor antagonist (antihistamine)
- ethanolamine
- sedative/hypnotic (tranquilizer)
- parasympatholytic (anticholinergic, antimuscarinic agent)
- anti-emetic
- antipruritic agent
More specific terms
Additional terms
Component of
- diphenhydramine/pramoxine/shampoo
- choline salicylate/diphenhydramine/phenylephrine
- choline salicylate/diphenhydramine
- camphor/diphenhydramine/zinc acetate
- brompheniramine/dextromethorphan/diphenhydramine/phenylephrine
- aspirin/citrate/diphenhydramine
- allantoin/diphenhydramine/fexofenadine
- acetaminophen/aspirin/citrate/diphenhydramine
- acetaminophen/aspirin/caffeine/diphenhydramine
- acetaminophen/aspirin/caffeine/citrate/diphenhydramine
- diphenhydramine/zinc/zinc acetate
- diphenhydramine/pramoxine
- diphenhydramine/phenylephrine/pseudoephedrine
- diphenhydramine/phenol
- diphenhydramine/menthol
- diphenhydramine/lidocaine/nystatin
- diphenhydramine/guaifenesin/phenylephrine
- cortisol/diphenhydramine/nystatin/tetracycline
- cortisol/diphenhydramine/nystatin
- codeine/diphenhydramine/phenylephrine/phosphate
- clemastine/diphenhydramine/pseudoephedrine
- citrate/diphenhydramine/pseudoephedrine
- carbetapentane/diphenhydramine/phenylephrine
- benzyl alcohol/calamine/diphenhydramine
- benzethonium/diphenhydramine/zinc acetate
- aspirin/citrate/diphenhydramine/nov protein
- aluminum hydroxide/diphenhydramine/lidocaine/magnesium hydroxide/simethicone
- allantoin/diphenhydramine
- acetaminophen/diphenhydramine/phenylephrine/pseudoephedrine
- acetaminophen/diphenhydramine/guaifenesin/phenylephrine
- acetaminophen/diphenhydramine/doxylamine
- acetaminophen/dextromethorphan/diphenhydramine/pseudoephedrine
- acetaminophen/dextromethorphan/diphenhydramine/guaifenesin/phenylephrine
- acetaminophen/citrate/diphenhydramine
- acetaminophen/chlorpheniramine/diphenhydramine/pseudoephedrine
- acetaminophen/chlorpheniramine/diphenhydramine/phenylephrine
- diphenhydramine/zinc acetate
- diphenhydramine/magnesium salicylate
- carbetapentane/diphenhydramine
- diphenhydramine/ibuprofen (Advil PM)
- citrate/diphenhydramine/ibuprofen
- diphenhydramine/salicylate
- diphenhydramine/pseudoephedrine
- diphenhydramine/hydrocodone/phenylephrine
- diphenhydramine/huntingtin/hydrocodone/phenylephrine
- diphenhydramine/guaifenesin
- acetic acid/diphenhydramine
- diphenhydramine/phenylephrine
- diphenhydramine/tripelennamine
- cortisol/diphenhydramine
- dextromethorphan/diphenhydramine/phenylephrine
- codeine/diphenhydramine/phenylephrine
- calamine/diphenhydramine
- aspirin/diphenhydramine
- acetaminophen/dextromethorphan/diphenhydramine
- acetaminophen/aspirin/diphenhydramine
- acetaminophen/diphenhydramine/pseudoephedrine
- acetaminophen/diphenhydramine
- acetaminophen/diphenhydramine/phenylephrine
- brompheniramine/diphenhydramine
- brompheniramine/diphenhydramine/phenylephrine
- acetaminophen/dextromethorphan/diphenhydramine/phenylephrine
- Benadryl/Carafate/Mylanta
- dimenhydrinate (Dramamine)
- magic mouthwash
- suppository anti-emetic combination (BRD)
- intravenous anti-emetic combination
References
- ↑ The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- ↑ Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
- ↑ Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995
- ↑ 4.0 4.1 Medications Can Cause Seizures Prescriber's Letter 10(3):16 2003 Detail-Document#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=190320&pb=PRL (subscription needed) http://www.prescribersletter.com
- ↑ 5.0 5.1 FDA Medwatch Benadryl Extra Strength Itch Stopping Gel: Packaging Changes to Reduce Use Errors http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm211792.htm
- ↑ 6.0 6.1 Deprecated Reference
- ↑ 7.0 7.1 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