- Drugs List
- Therapeutic Indications
- Precautions and Warnings
- Pregnancy and Lactation
- Side Effects
Oral formulations of diphenhydramine hydrochloride.
Insomnia (short-term treatment)
Individual brands may vary in their dosage recommendations and maximum daily dosage.
25mg to 50mg at bedtime or if unable to sleep.
20mg to 50mg three or four times a day. Do not exceed 300mg in any 24 hour period.
Side effects are more likely to occur in the elderly. Use the normal adult dose cautiously but reduce if necessary.
Children over 16 years
25mg to 50mg at bedtime or after retiring if sleep is not forthcoming.
Children over 12 Years
(See Dosage; Adults)
Children 6 to 12 years
10mg three times a day.
Children 1 to 5 years
5mg to 10mg three times a day.
Children under 1 year
5mg three times a day.
2 weeks prior to estimated delivery date
Precautions and Warnings
Children under 16 years
Within 2 weeks of discontinuing MAOIs
Benign prostatic hyperplasia
Bladder outflow obstruction
Central nervous system depression
Chronic obstructive pulmonary disease
Glucose-galactose malabsorption syndrome
Hereditary fructose intolerance
Moderate hepatic impairment
Moderate renal impairment
Stenosing peptic ulcer
Advise patient drowsiness may affect ability to drive or operate machinery
Not all available brands are licensed for all indications
Some formulations contain lactose
Some formulations contain sucrose
Tolerance may develop with continued use
Not licensed for all indications in all age groups
Should not be taken with other cough or cold medicine
Advise patient to avoid alcohol during treatment
Advise patient not to exceed stated dose
Advise patient to consult a doctor if symptoms persist despite treatment
Pregnancy and Lactation
Use diphenhydramine with caution in pregnancy.
The majority of published human and animal data suggests that diphenhydramine does not cause complications in pregnancy. Some sources, however, have indentified a statistical association with cleft palate following first trimester exposure. Premature infants exposed within two weeks of birth may be at risk of toxicity.
The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Use diphenhydramine with caution in breastfeeding.
Small amounts of antihistamines are excreted in breast milk.
Data is limited in humans but expected breast milk concentrations are not thought to be sufficiently high to affect a nursing infant.
The Drug and Lactation Database (LactMed) states that small, occasional doses of diphenhydramine would not be expected to cause any adverse effects in the breastfed infants. Larger doses or more prolonged use may cause effects in the infant or decrease the milk supply. The non-sedating antihistamines are preferred alternatives.
Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1
Difficulty in micturition
Thickening of bronchial secretions
It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.
The following number will direct the caller to the relevant local centre (0844) 892 0111
Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Last Full Review Date: November 2017.
Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 10th edition (2015) ed. Briggs, G., Freeman, R. Wolters Kluwer Health, Philadelphia.
Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 3rd edition (2015) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.
Summary of Product Characteristics: Galpharm One a Night Nightcalm. Galpharm International. Revised November 2015.
Summary of Product Characteristics: Histergan/NightAid/Paxidorm/Sleep Aid tablets 25mg. Norma Chemicals Ltd. Revised March 2017.
Summary of Product Characteristics: Lunox Sleep Aid 25mg tablets. Crescent Pharma Limited. Revised April 2016.
Summary of Product Characteristics: Lunox Max Strength Sleep Aid 50mg tablets. Crescent Pharma Limited. Revised June 2016.
Summary of Product Characteristics: Nytol One-A-Night. Omega Pharma Ltd. Revised January 2016.
Summary of Product Characteristics: Nytol Original. Omega Pharma Ltd. Revised January 2016.
Summary of Product Characteristics: Nytol Simply Sleep Hot Chocolate 50mg Powder for Oral Solution. Omega Pharma Ltd. Revised January 2017.
NICE Evidence Services Available at: www.nice.org.uk Last accessed: 15 June 2017
US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
Available at: https://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT
Diphenhydramine; Last revised: 7 September 2013
Last accessed: 15 March 2017
The Norwegian Porphyria Centre (NAPOS).
Available at: https://www.drugs-porphyria.com/languages/UnitedKingdom/s1.php?l=gbr
Last accessed: 15 March 2017
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Medscape UK | Univadis prescription drug monographs & interactions are based on FDB Multilex Content
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