DIPHENHYDRAMINE
Brand names Medinex, Nytol
Used in the following combined preparations Benylin, Caladryl, Guanor, Histalix, Propain, Uniflu
GENERAL INFORMATION
Diphenhydramine is one of the oldest antihistamines, having been in use for over 40 years. Like many other older antihistamines, diphenhydramine has a wide range of actions and can be used as an anti-emetic or antihistamine, but it is most widely used for its anticholinergic properties. Its primary use is in a range of cough and cold remedies. In tablet form it is used to treat hay fever.
Diphenhydramine is also an ingredient in creams and lotions used to treat urticaria, insect bites and stings, and skin allergies.
When it is taken by mouth, this drug has a marked sedative action and often causes drowsiness. Its sedative effect is used in over-the-counter preparations to relieve temporary sleep disorders.
INFORMATION FOR USERS
Follow instructions on the label. Call your doctor if symptoms worsen.
How taken
Tablets, liquid, cream, lotion.
Frequency and timing of doses
The frequency varies according to the preparation being used. Follow the instructions on the container.
Adult dosage range
For sleep disorders: 50mg at night. For other conditions: dosage varies according to the preparation being used.
Onset of effect
Within 45 minutes (by mouth).
Duration of action
4-6 hours.
Diet advice
None.
Storage
Keep in a closed container in a cool, dry place out of the reach of children.
Missed dose
Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.
Stopping the drug
Can be safely stopped as soon as you no longer need it.
Exceeding the dose
An occasional unintentional extra dose is unlikely to cause problems. Large overdoses may cause drowsiness or agitation. Notify your doctor.
QUICK REFERENCE
Drug group Antihistamine, anti-emetic, and drug for Parkinsonism
Overdose danger rating Medium
Dependence rating Low
Prescription needed No
Available as generic No
SPECIAL PRECAUTIONS
Be sure to consult your doctor or pharmacist before taken this drug if:
You have a long-term liver problem.
You have myasthenia gravis.
You have glaucoma.
You have urinary difficulties.
Pregnancy
No evidence of risk.
POSSIBLE ADVERSE EFFECTS
Drowsiness is the most common adverse effect of diphenhydramine. Other side effects,
such as dry mouth and blurred vision, are due to its anticholinergic action.
INTERACTIONS
Anticholinergic drugs are likely to increase the anticholinergic effects of diphenhydramine.
Sedatives
All sedatives are likely to enhance the sedative effect of this drug.
Breast-feeding
The drug passes into the breast milk, but at normal doses adverse effects on the baby are unlikely. Discuss with your doctor.
Infants and children
Not recommended for newborn or premature infants. Reduced dose necessary for older children.
Over 60
Reduced dose may be necessary. Increased likelihood of adverse effects.
Driving and hazardous work
Avoid such activities until you have learned how diphenhydramine affects you because the drug can cause drowsiness.
Alcohol
Avoid. Alcohol increases the sedative effects of this drug.
PROLONGED USE
The effect of this drug may become weaker with prolonged use over a period of weeks or months as the body adapts.
