Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2017 Publisher: Norma Chemicals Ltd., 51-53 Stert Street, Abingdon, Oxfordshire OX14 3JF United Kingdom
Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.
Contraindicated for use in patients with the following conditions: stenosing peptic ulcer, pyloroduodenal obstruction.
When used as a sleep aid: Sedation of children under the age of 16 should only be under medical direction, consequently use as a sedative in this age group is contraindicated.
Diphenhydramine should be used with caution in patients with myasthenia gravis,epilepsy or seizure disorders, prostatic hypertrophy, urinary retention, narrow-angle glaucoma, asthma, bronchitis and chronic obstructive pulmonary disease (COPD), moderate to severe hepatic impairment and moderate to severe renal impairment.
Tolerance may develop with continuous use. Seek medical advice if sleeplessness persists, as insomnia may be a symptom of a serious underlying medical illness.
May increase the effects of alcohol, therefore alcohol should be avoided. Avoid use of other antihistamine-containing preparations, including topical antihistamines and cough and cold medicines.
Use with caution in the elderly, who are more likely to experience side-effects. Avoid use in elderly patients with confusion.
Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not take this medicine.
Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.
Diphenhydramine may potentiate the sedative effects of alcohol and other CNS depressants (e.g. tranquillizers, hypnotics and anxiolytics).
Monoamine oxidase inhibitors (MAOIs) prolong and intensify the anticholinergic effects of diphenhydramine. The product should be used with caution with MAOIs or within 2 weeks of stopping an MAOI.
As diphenhydramine has some antimuscarinic activity, the effects of some anticholinergic drugs (e.g. atropine, tricyclic antidepressants) may be potentiated therefore medical advice should be sought before taking diphenhydramine with such medicines.
Diphenhydramine is an inhibitor of the cytochrome p450 isoenzyme CYP2D6. Therefore, there may be a potential for interaction with drugs which are primarily metabolised by CYP2D6, such as metoprolol and venlafaxine.
Diphenhydramine should not be used in patients receiving any of the above drugs unless directed by a doctor.
Diphenhydramine crosses the placenta. Because animal reproduction studies are not always predictive of human response and since there is inadequate experience with use of diphenhydramine in pregnant women, the potential risk for humans is unknown. Use of sedating antihistamines during the third trimester may result in reactions in the newborn or premature neonates. This drug is not recommended during pregnancy. Consult a doctor before use.
Diphenhydramine has been detected in breast milk, but the effect of this on breastfed infants is unknown. Diphenhydramine is not recommended for use during lactation. Consult a doctor before use.
Diphenhydramine is a hypnotic and will produce drowsiness or sedation soon after the dose has been taken. It may also cause dizziness, blurred vision, cognitive and psychomotor impairment. These can seriously affect the patient’s ability to drive and use machines. If affected, do not drive or operate machinery.
Specific estimation of the frequency of adverse events for OTC products is inherently difficult (particularly numerator data). Adverse reactions which have been observed in clinical trials and which are considered to be common (occurring in >1/100 to <1/10) or very common (occurring in >1/10) are listed below by MedDRA System Organ Class. The frequency of other adverse reactions identified during postmarketing use is unknown, but these reactions are likely to be uncommon (occurring in >1/1,000 to <1/100) or rare (occurring in <1/1000).
| System Organ Class | Very Common ≥1/10 | Common ≥1/100, <1/10 | Uncommon ≥1/1,000, <1/100 | Rare ≥1/10,000, <1/1000 | Very Rare <1/10,000 | Not known (cannot be estimated from available data) |
|---|---|---|---|---|---|---|
| Cardiac Disorders | tachycardia, palpitations, arrhythmias | |||||
| Eye Disorders | blurred vision | |||||
| General disorders and administration site conditions | fatigue | |||||
| Gastrointestinal Disorders | dry mouth | gastrointestinal disturbance including nausea, vomiting | ||||
| Immune System Disorders | hypersensitivity reactions including rash, urticaria, dyspnoea and angioedema | |||||
| Musculoskeletal and connective tissue Disorders | muscle twitching | |||||
| Nervous System Disorders | sedation, drowsiness, disturbance in attention, unsteadiness, dizziness | convulsions, headache, paraesthesia, dyskinesias | ||||
| Psychiatric Disorders | confusion, paradoxical excitation (e.g. increased energy, restlessness, nervousness), depression, sleep disturbances * The elderly are more prone to confusion and paradoxical excitation. | |||||
| Renal and urinary disorders | urinary difficulty, urinary retention | |||||
| Respiratory, thoracic and mediastinal disorders | thickening of bronchial secretions |
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme, website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.
Incompatible with barbiturates and iodo compounds in solution.
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