GlaxoSmithKline Consumer Healthcare

Pregnancy

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.

Lactation

Diphenhydramine has been detected in breast milk, but the effect of this on breastfed infants is unknown. Nytol is not recommended for use during lactation. Consult a doctor before use.

Nytol 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 post-marketing use is unknown, but these reactions are likely to be uncommon (occurring in > 1/1,000 to <1/100) or rare (occurring in < 1/1,000).

General disorders and administration site conditions:

Common: fatigue

Immune system disorders:

Unknown: Hypersensitivity reactions including rash, urticaria, dyspnoea and angioedema

Psychiatric disorders*:

Unknown: confusion, paradoxical excitation (e.g. increased energy, restlessness, nervousness)

* The elderly are more prone to confusion and paradoxical excitation.

Nervous system disorders:

Common: sedation, drowsiness, disturbance in attention, unsteadiness, dizziness,

Unknown: convulsions, headache, paraesthesia, dyskinesias

Eye disorders:

Unknown: blurred vision

Cardiac disorders:

Unknown: tachycardia, palpitations

Respiratory, thoracic and mediastinal disorders:

Unknown: thickening of bronchial secretions

Gastrointestinal disorders:

Common: dry mouth

Unknown: gastrointestinal disturbance including nausea, vomiting

Musculoskeletal and connective tissue disorders:

Unknown: muscle twitching

Renal and urinary disorders:

Unknown: urinary difficulty, urinary retention

Overdose is likely to result in effects similar to those listed under adverse reactions. Additional symptoms may include mydriasis, fever, flushing, agitation, tremor, dystonic reactions, hallucinations and ECG changes. Large overdose may cause rhabdomyolysis, convulsions, delirium, toxic psychosis, arrhythmias, coma and cardiovascular collapse.

Treatment should be supportive and directed towards specific symptoms.  Convulsions and marked CNS stimulation should be treated with parenteral diazepam.

The name of the medicincal product has changed from Nytol to Nytol Original 25mg Tablets.

Section 4.5, has been re-worded and now states the following:

Diphenhydramine may potentiate the sedative effects of alcohol and other CNS depressants (e.g. tranquillizers, hypnotics and anxiolytics).

Monoamine oxidase inhibitors (MAOI) 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.