WARNINGS
Antihistamines
should be used with considerable caution in patients with narrow-angle
glaucoma, stenosing peptic ulcer, pyloroduodenal obstruction,
symptomatic prostatic hypertrophy or bladder-neck obstruction.
Local necrosis has
been associated with the use of subcutaneous or intradermal use of
intravenous diphenhydramine.
Use in Pediatric Patients
In
pediatric patients, especially, antihistamines in overdosage may cause
hallucinations, convulsions or death.
As in
adults, antihistamines may diminish mental alertness in
pediatric patients. In the young pediatric patient,
particularly, they may produce excitation.
Use in the Elderly (approximately 60 years or older)
Antihistamines are more likely to cause dizziness, sedation and
hypotension in elderly patients.
PRECAUTIONS
General
Diphenhydramine hydrochloride has an atropine-like action and,
therefore, should be used with caution in patients with a
history of bronchial asthma, increased intraocular pressure,
hyperthyroidism, cardiovascular disease or hypertension. Use
with caution in patients with lower respiratory disease,
including asthma.
Information for Patients
Patients
taking diphenhydramine hydrochloride should be advised that this
drug may cause drowsiness and has an additive effect with
alcohol.
Patients
should be warned about engaging in activities requiring mental
alertness, such as driving a car or operating appliances,
machinery, etc.
Drug Interactions
Diphenhydramine hydrochloride has additive effects with alcohol
and other CNS depressants (hypnotics, sedatives, tranquilizers,
etc.)
MAO
inhibitors prolong and intensify the anticholinergic (drying)
effects of antihistamines.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Long-term
studies in animals to determine mutagenic and carcinogenic
potential have not been performed.
Pregnancy
Teratogenic Effects—Pregnancy Category B
Reproduction studies have been performed in rats and
rabbits at doses up to 5 times the human dose and have
revealed no evidence of impaired fertility or harm to
the fetus due to diphenhydramine hydrochloride. There
are, however, no adequate and well-controlled studies in
pregnant women. Because animal reproduction studies are
not always predictive of human response, this drug
should be used during pregnancy only if clearly
needed.
Pediatric Use
Diphenhydramine should not be used in neonates and premature infants (see
CONTRAINDICATIONS).
Diphenhydramine may diminish mental alertness, or in the young pediatric patient, cause excitation. Overdosage may cause hallucinations, convulsions or death (see
WARNINGS
and
OVERDOSAGE).
See also
DOSAGE AND ADMINISTRATION
section.
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