Diphenhydramine
Nytol, others | |
AHFS/Drugs.com | Monograph |
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MedlinePlus | a682539 |
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ATC code | |
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Pharmacokinetic data | |
Bioavailability | 40–60%[4] |
Protein binding | 98–99% |
Metabolism | Liver (CYP2D6, others)[8][9] |
Elimination half-life | Range: 2.4–13.5 h[5][4][6] |
Excretion | Urine: 94%[7] Feces: 6%[7] |
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Diphenhydramine (DPH) is an
Common side effects include sleepiness, poor coordination and an upset stomach.[10] Its use is not recommended in young children or the elderly.[10][11] There is no clear risk of harm when used during pregnancy; however, use during breastfeeding is not recommended.[12] It is a first-generation H1-antihistamine and it works by blocking certain effects of histamine, which produces its antihistamine and sedative effects.[10][2] Diphenhydramine is also a potent anticholinergic, which means it also works as a deliriant at much higher than recommended doses as a result.[13] Its sedative and deliriant effects have led to some cases of recreational use.[14][2]
Diphenhydramine was first developed by
Medical uses
Diphenhydramine is a first-generation antihistamine used to treat a number of conditions including
Allergies
Diphenhydramine is effective in treatment of allergies.[22] As of 2007[update], it was the most commonly used antihistamine for acute allergic reactions in the emergency department.[23]
By injection it is often used in addition to epinephrine for anaphylaxis,[24] although as of 2007[update] its use for this purpose had not been properly studied.[25] Its use is only recommended once acute symptoms have improved.[22]
Topical formulations of diphenhydramine are available, including creams, lotions, gels, and sprays. These are used to relieve itching and have the advantage of causing fewer systemic effects (e.g., drowsiness) than oral forms.[26]
Movement disorders
Diphenhydramine is used to treat akathisia and Parkinson's disease–like extrapyramidal symptoms caused by antipsychotics.[27] It is also used to treat acute dystonia including torticollis and oculogyric crisis caused by first generation antipsychotics.
Sleep
Because of its
Diphenhydramine has also been used off-prescription by parents in an attempt to make their children sleep and to sedate them on long-distance flights.[30] This has been met with criticism, both by doctors and by members of the airline industry, because sedating passengers may put them at risk if they cannot react efficiently to emergencies,[31] and because the drug's side effects, especially the chance of a paradoxical reaction, may make some users hyperactive. Addressing such use, the Seattle Children's hospital argued, in a 2009 article, "Using a medication for your convenience is never an indication for medication in a child."[32]
The
Nausea
Diphenhydramine also has antiemetic properties, which make it useful in treating the nausea that occurs in vertigo and motion sickness. However, when taken above recommended doses, it can cause nausea (especially above 200 mg).[35]
Special populations
Diphenhydramine is not recommended for people older than 60 and children younger than six, unless a physician is consulted.
Diphenhydramine is excreted in breast milk.[40] It is expected that low doses of diphenhydramine taken occasionally will cause no adverse effects in breastfed infants. Large doses and long-term use may affect the baby or reduce breast milk supply, especially when combined with sympathomimetic drugs, such as pseudoephedrine, or before the establishment of lactation. A single bedtime dose after the last feeding of the day may minimize harmful effects of the medication on the baby and on the milk supply. Still, non-sedating antihistamines are preferred.[41]
Paradoxical reactions to diphenhydramine have been documented, particularly in children, and it may cause excitation instead of sedation.[42]
Topical diphenhydramine is sometimes used especially for people in hospice. This use is without indication and topical diphenhydramine should not be used as treatment for nausea because research has not shown that this therapy is more effective than others.[43]
There were no documented cases of clinically apparent acute liver injury caused by normal doses of diphenhydramine.[44]
Adverse effects
The most prominent side effect is sedation. A typical dose creates driving impairment equivalent to a blood-alcohol level of 0.10, which is higher than the 0.08 limit of most drunk-driving laws.[23]
Diphenhydramine is a potent
Some individuals experience an
Conditions such as restlessness or akathisia can worsen from increased levels of diphenhydramine, especially with recreational dosages.[42] Normal doses of diphenhydramine, like other first generation antihistamines, can also make symptoms of restless legs syndrome worse.[49] As diphenhydramine is extensively metabolized by the liver, caution should be exercised when giving the drug to individuals with hepatic impairment.
Anticholinergic use later in life is associated with an increased risk for cognitive decline and dementia among older people.[50]
Contraindications
Diphenhydramine is contraindicated in premature infants and neonates, as well as people who are breastfeeding. It is a pregnancy Category B drug. Diphenhydramine has additive effects with alcohol and other CNS depressants. Monoamine oxidase inhibitors prolong and intensify the anticholinergic effect of antihistamines.[51]
Overdose
Diphenhydramine is one of the most commonly misused over-the-counter drugs in the United States.[52] In cases of extreme overdose, if not treated in time, acute diphenhydramine poisoning may have serious and potentially fatal consequences. Overdose symptoms may include:[53]
- Abdominal pain
- Abnormal speech (inaudibility, forced speech, etc.)
- Acute megacolon
- Anxiety/nervousness
- Coma
- Death
- Delirium
- Disorientation
- Dissociation
- Euphoria or dysphoria
- Extreme drowsiness
- Flushed skin
- Hallucinations (auditory, visual, tactile, etc.)
- Heart palpitations
- Inability to urinate
- Motor disturbances
- Muscle spasms
- Seizures
- Severe dizziness
- Severe mouth and throat dryness
- Tremors
- Vomiting
Acute poisoning can be fatal, leading to cardiovascular collapse and death in 2–18 hours, and in general is treated using a symptomatic and supportive approach.
Interactions
Alcohol may increase the drowsiness caused by diphenhydramine.[57][58]
Pharmacology
Pharmacodynamics
Site | Ki (nM) | Species | Ref |
---|---|---|---|
SERT | ≥3,800 | Human | [60][61] |
NET | 960–2,400 | Human | [60][61] |
DAT | 1,100–2,200 | Human | [60][61] |
5-HT2C | 780 | Human | [61] |
α1B | 1,300 | Human | [61] |
α2A | 2,900 | Human | [61] |
α2B | 1,600 | Human | [61] |
α2C | 2,100 | Human | [61] |
D2 |
20,000 | Rat | [62] |
H1 | 9.6–16 | Human | [63][61] |
H2 | >100,000 | Canine | [64] |
H3 | >10,000 | Human | [61][65][66] |
H4 | >10,000 | Human | [66] |
M1 | 80–100 | Human | [67][61] |
M2 | 120–490 | Human | [67][61] |
M3 | 84–229 | Human | [67][61] |
M4 | 53–112 | Human | [67][61] |
M5 | 30–260 | Human | [67][61] |
VGSC |
48,000–86,000 | Rat | [68] |
hERG |
27,100 ( IC50 ) |
Human | [69] |
Values are Ki (nM), unless otherwise noted. The smaller the value, the more strongly the drug binds to the site. |
Diphenhydramine, available in various salt forms,[70] such as citrate,[71][72] hydrochloride,[73] and salicylate,[74] exhibits distinct molecular weights and pharmacokinetic properties. Specifically, diphenhydramine hydrochloride and diphenhydramine citrate possess molecular weights of 291.8 g/mol[75] and 447.5 g/mol,[76] respectively. These variations in molecular weight influence the dissolution rates and absorption characteristics of each salt form. Consequently, a dose of 25 mg diphenhydramine hydrochloride is therapeutically equivalent to 38 mg of diphenhydramine citrate. As such, dosage adjustments are necessary to account for these differences when switching between salt forms.[77]
Diphenhydramine, while traditionally known as an antagonist, acts primarily as an inverse agonist of the histamine H1 receptor.[78] It is a member of the ethanolamine class of antihistaminergic agents.[37] By reversing the effects of histamine on the capillaries, it can reduce the intensity of allergic symptoms. It also crosses the blood–brain barrier and inversely agonizes the H1 receptors centrally.[78] Its effects on central H1 receptors cause drowsiness.
Diphenhydramine is a potent
Diphenhydramine also acts as an intracellular
Biological target | Mode of action | Effect |
---|---|---|
H1 receptor | Inverse agonist | Allergy reduction; Sedation |
mACh receptors | Antagonist |
Anticholinergic; Antiparkinson
|
Sodium channels | Blocker | Local anesthetic |
Pharmacokinetics
Oral bioavailability of diphenhydramine is in the range of 40% to 60%, and peak plasma concentration occurs about 2 to 3 hours after administration.[4]
The primary route of metabolism is two successive
The
Chemistry
Diphenhydramine is a
Detection in body fluids
Diphenhydramine can be quantified in blood, plasma, or serum.[86] Gas chromatography with mass spectrometry (GC-MS) can be used with electron ionization on full scan mode as a screening test. GC-MS or GC-NDP can be used for quantification.[86] Rapid urine drug screens using immunoassays based on the principle of competitive binding may show false-positive methadone results for people having ingested diphenhydramine.[87] Quantification can be used to monitor therapy, confirm a diagnosis of poisoning in people who are hospitalized, provide evidence in an impaired driving arrest, or assist in a death investigation.[86]
History
Diphenhydramine was discovered in 1943 by George Rieveschl, a former professor at the University of Cincinnati.[88][89] In 1946, it became the first prescription antihistamine approved by the U.S. FDA.[90]
In the 1960s, diphenhydramine was found to weakly inhibit reuptake of the neurotransmitter serotonin.[80] This discovery led to a search for viable antidepressants with similar structures and fewer side effects, culminating in the invention of fluoxetine (Prozac), a selective serotonin reuptake inhibitor (SSRI).[80][91] A similar search had previously led to the synthesis of the first SSRI, zimelidine, from brompheniramine, also an antihistamine.[92]
In 1975, diphenhydramine was still available only by prescription in the U.S. and required medical supervision.[93]
Society and culture
Diphenhydramine is deemed to have limited abuse potential in the United States owing to its potentially serious side-effect profile and limited euphoric effects, and is not a controlled substance. Since 2002, the U.S. FDA has required special labeling warning against use of multiple products that contain diphenhydramine.[94] In some jurisdictions, diphenhydramine is often present in postmortem specimens collected during investigation of sudden infant deaths; the drug may play a role in these events.[95][96]
Diphenhydramine is among prohibited and controlled substances in the
Recreational use
Although diphenhydramine is widely used and generally considered to be safe for occasional usage, multiple cases of abuse and addiction have been documented.[14] Because the drug is cheap and sold over the counter in most countries, adolescents without access to more sought-after illicit drugs, are particularly at risk.[99] People with mental health problems—especially those with schizophrenia—are also prone to abuse the drug, which is self-administered in large doses to treat extrapyramidal symptoms caused by the use of antipsychotics.[100]
Recreational users report calming effects, mild euphoria, and hallucinations as the desired effects of the drug.[100][101] Research has shown that antimuscarinic agents, including diphenhydramine, "may have antidepressant and mood-elevating properties".[102] A study conducted on adult males with a history of sedative abuse found that subjects who were administered a high dose (400 mg) of diphenhydramine reported a desire to take the drug again, despite also reporting negative effects, such as difficulty concentrating, confusion, tremors, and blurred vision.[103]
In 2020, an Internet challenge emerged on social media platform TikTok involving deliberately overdosing on diphenhydramine; dubbed the Benadryl challenge, the challenge encourages participants to consume dangerous amounts of Benadryl for the purpose of filming the resultant psychoactive effects the hallucinations can include a visit from the "Hat Man" as recreational users call him, and has been implicated in several hospitalizations[104] and at least two deaths.[105][106][107]
Names
Diphenhydramine is sold under the brand name
Procter & Gamble markets an over-the-counter formulation of diphenhydramine as a sleep aid under the brand ZzzQuil.[109]
References
- ISBN 978-0-8247-4497-7.
- ^ PMID 29620065.
- ^ "Benylin Chesty Coughs (Original) - Summary of Product Characteristics (SmPC)". (emc). 24 February 2022. Archived from the original on 30 December 2022. Retrieved 29 December 2022.
- ^ S2CID 33541001.
- ^ a b AHFS Drug Information. Published by authority of the Board of Directors of the American Society of Hospital Pharmacists. 1990. Archived from the original on 14 January 2023. Retrieved 9 October 2017.
- ^ S2CID 25452263.
- ^ PMID 3962845.
- ^ PMID 19153052.
- ^ "Showing Diphenhydramine (DB01075)". DrugBank. Archived from the original on 31 August 2009. Retrieved 5 September 2009.
- ^ a b c d e f g h i "Diphenhydramine Hydrochloride". Drugs.com. American Society of Health-System Pharmacists. 6 September 2016. Archived from the original on 15 September 2016. Retrieved 28 September 2016.
- ^ PMID 27751669.
- ^ "Diphenhydramine Pregnancy and Breastfeeding Warnings". Drugs.com. Archived from the original on 2 October 2016. Retrieved 28 September 2016.
- ISBN 978-0-7817-2468-5. Archivedfrom the original on 8 September 2017.
- ^ S2CID 45490366.
- ISBN 978-3-527-64565-7. Archivedfrom the original on 2 October 2016.
- ^ "Benadryl". Ohio History Central. Archived from the original on 17 October 2016. Retrieved 28 September 2016.
- ^ "The Top 300 of 2021". ClinCalc. Archived from the original on 15 January 2024. Retrieved 14 January 2024.
- ^ "Diphenhydramine - Drug Usage Statistics". ClinCalc. Retrieved 14 January 2024.
- ^ "Diphenhydramine Hydrochloride Monograph". Drugs.com. The American Society of Health-System Pharmacists. Archived from the original on 15 June 2011.
- ^ Brown HE, Stoklosa J, Freudenreich O (December 2012). "How to stabilize an acutely psychotic patient" (PDF). Current Psychiatary. 11 (12): 10–16. Archived from the original (PDF) on 14 May 2013.
- PMID 10456039.
- ^ a b American Society of Health-System Pharmacists. "Diphenhydramine Hydrochloride". Drugs.com. Archived from the original on 15 September 2016. Retrieved 2 August 2016.
- ^ S2CID 7596980.
- ISBN 978-0-07-170107-5.
- PMID 17253584.
- ^ "Diphenhydramine Topical". MedlinePlus. Archived from the original on 10 October 2020. Retrieved 9 October 2020.
- ISBN 978-0-07-176401-8.
- ^ Monson K, Schoenstadt A (8 September 2013). "Benadryl Addiction". eMedTV. Archived from the original on 4 January 2014.
- PMID 9709726.
- ^ Crier F (2 August 2017). "Is it wrong to drug your children so they sleep on a flight?". The Telegraph. Archived from the original on 11 January 2022. Retrieved 13 April 2020.
- ^ Morris R (3 April 2013). "Should parents drug babies on long flights?". BBC News. Archived from the original on 8 March 2021. Retrieved 13 April 2020.
- ^ Swanson WS (25 November 2009). "If It Were My Child: No Benadryl for the Plane". Seattle Children's. Archived from the original on 25 February 2021. Retrieved 13 April 2020.
- PMID 27998379.
- S2CID 250536370.
- from the original on 24 March 2016. Retrieved 10 March 2016.
- ISBN 978-1-56363-341-6.
- ^ ISBN 978-0-07-162442-8.
- ^ "High risk medications as specified by NCQA's HEDIS Measure: Use of High Risk Medications in the Elderly" (PDF). National Committee for Quality Assurance (NCQA). Archived from the original (PDF) on 1 February 2010.
- ^ "2012 AGS Beers List" (PDF). The American Geriatrics Society. Archived from the original (PDF) on 12 August 2012. Retrieved 27 November 2015.
- PMID 11456429.
- PMID 30000938.
- ^ S2CID 10856872.
- ABIM Foundation, American Academy of Hospice and Palliative Medicine, archivedfrom the original on 1 September 2013, retrieved 1 August 2013, which cites
- Smith TJ, Ritter JK, Poklis JL, Fletcher D, Coyne PJ, Dodson P, Parker G (May 2012). "ABH gel is not absorbed from the skin of normal volunteers". Journal of Pain and Symptom Management. 43 (5): 961–6. PMID 22560361.
- Weschules DJ (December 2005). "Tolerability of the compound ABHR in hospice patients". Journal of Palliative Medicine. 8 (6): 1135–43. PMID 16351526.
- Smith TJ, Ritter JK, Poklis JL, Fletcher D, Coyne PJ, Dodson P, Parker G (May 2012). "ABH gel is not absorbed from the skin of normal volunteers". Journal of Pain and Symptom Management. 43 (5): 961–6.
- from the original on 29 July 2021. Retrieved 21 June 2021.
- ^ "Diphenhydramine Side Effects". Drugs.com. Archived from the original on 24 January 2009. Retrieved 6 April 2009.
- ISBN 978-0-08-093289-7. Archivedfrom the original on 8 March 2021. Retrieved 4 March 2020.
- S2CID 32839996.
- PMID 6219138.
- ^ "Restless Legs Syndrome Fact Sheet". National Institute of Neurological Disorders and Stroke. Archived from the original on 28 July 2017. Retrieved 27 August 2019.
- PMID 25879993.
- from the original on 28 May 2022. Retrieved 27 December 2021.
- PMID 32491510.
- ^ "Diphenhydramine overdose". MedlinePlus Medical Encyclopedia. U.S. National Library of Medicine. Archived from the original on 30 May 2013.
- ^ ISBN 978-0-07-166833-0. Retrieved 19 March 2013.
- PMID 9918600.
- S2CID 5602304.
- ^ "Diphenhydramine and Alcohol / Food Interactions". Drugs.com. Archived from the original on 17 February 2013.
- PMID 10344773.
- ^ Roth BL, Driscol J. "PDSP Ki Database". Psychoactive Drug Screening Program (PDSP). University of North Carolina at Chapel Hill and the United States National Institute of Mental Health. Archived from the original on 20 April 2019. Retrieved 14 August 2017.
- ^ PMID 9537821.
- ^ PMID 23357028.
- S2CID 19420332.
- PMID 16782354.
- PMID 1703298.
- S2CID 25542667.
- ^ S2CID 123619.
- ^ PMID 1346637.
- ^ S2CID 18560451.
- S2CID 40355762.
- .
- S2CID 97766056.
- PMID 21439118.
- S2CID 45456788.
- S2CID 43642257.
- ^ "Diphenhydramine Hydrochloride". PubChem. U.S. National Library of Medicine.
- ^ "Diphenhydramine citrate". PubChem. U.S. National Library of Medicine.
- ^ Pope C (28 August 2023). "Diphenhydramine Hydrochloride vs Citrate: What's the difference?". drugs.com.
- ^ PMID 22021988.
- ^ Lopez AM (10 May 2010). "Antihistamine Toxicity". Medscape Reference. WebMD LLC. Archived from the original on 13 October 2010.
- ^ PMID 10511010.
- S2CID 45054719.
- PMID 16168438.
- PMID 4402747.
- S2CID 24989721.
- PMID 28967696.
- ^ ISBN 978-0-444-52214-6.
- S2CID 31581678.
- ^ Hevesi D (29 September 2007). "George Rieveschl, 91, Allergy Reliever, Dies". The New York Times. Archived from the original on 13 December 2011. Retrieved 14 October 2008.
- ^ "Benadryl". Ohio History Central. Archived from the original on 5 September 2015. Retrieved 13 August 2015.
- ^ Ritchie J (24 September 2007). "UC prof, Benadryl inventor dies". Business Courier of Cincinnati. Archived from the original on 24 December 2008. Retrieved 14 October 2008.
- from the original on 11 March 2016. Retrieved 19 March 2013.
- ISBN 978-0-19-515130-5.
- Newspapers.com.
- from the original on 5 November 2008.
- PMID 16419411.
- ISBN 978-0-9626523-7-0.
- ^ "List of prohibited and controlled drugs according to chapter 96 of the laws of Zambia". The Drug Enforcement Commission ZAMBIA. Archived from the original (DOC) on 16 November 2013. Retrieved 20 March 2013.
- ^ "Zambia". Country Information > Zambia. Bureau of Consular Affairs, U.S. Department of State. Archived from the original on 21 July 2015. Retrieved 17 July 2015.
- ^ Forest E (27 July 2008). "Atypical Drugs of Abuse". Articles & Interviews. Student Doctor Network. Archived from the original on 27 May 2013.
- ^ S2CID 46619422. Archived from the original(PDF) on 2 August 2020. Retrieved 23 December 2017.
- PMID 21186972.
- S2CID 31355546.
- .
- ^ "TikTok Videos Encourage Viewers to Overdose on Benadryl". TikTok Videos Encourage Viewers to Overdose on Benadryl. Archived from the original on 8 October 2020. Retrieved 9 October 2020.
- ^ "Dangerous 'Benadryl Challenge' on Tik Tok may be to blame for the death of Oklahoma teen". KFOR.com Oklahoma City. 28 August 2020. Archived from the original on 2 August 2021. Retrieved 9 October 2020.
- ^ "Teen's Death Prompts Warning on 'Benadryl Challenge'". www.medpagetoday.com. 25 September 2020. Archived from the original on 29 September 2020. Retrieved 9 October 2020.
- ^ "What is the Benadryl challenge? New TikTok challenge that's left 13-year-old dead". The Independent. 23 April 2023. Retrieved 23 April 2023.
- ^ "Childrens Benadryl Allergy (solution) Johnson & Johnson Consumer Inc., McNeil Consumer Healthcare Division". Drugs.com. Archived from the original on 29 July 2020. Retrieved 26 November 2019.
- ^ "Is P&G Preparing to Expand ZzzQuil?". Archived from the original on 11 February 2017. Retrieved 10 February 2017.
- ^ "Mother To Baby | Fact Sheets [Internet]: Diphenhydramine". National Library of Medicine. January 2023. Retrieved 16 April 2024.
Further reading
- Björnsdóttir I, Einarson TR, Gudmundsson LS, Einarsdóttir RA (December 2007). "Efficacy of diphenhydramine against cough in humans: a review". Pharmacy World & Science. 29 (6): 577–83. S2CID 8168920.
- Cox D, Ahmed Z, McBride AJ (March 2001). "Diphenhydramine dependence". Addiction. 96 (3): 516–7. PMID 11310441.
- Lieberman JA (2003). "History of the use of antidepressants in primary care" (PDF). Primary Care Companion J. Clinical Psychiatry. 5 (supplement 7): 6–10. Archived from the original (PDF) on 11 June 2014. Retrieved 19 March 2013.
External links
Media related to Diphenhydramine at Wikimedia Commons