A1,
A2,
B,
C1,
C2,
D,
E,
F,
G-H,
I-K,
L,
M,
N,
O,
P1,
P2,
Q-R,
S,
T,
U-V,
W-Z
Clemastin Overdose, Contraindications and Information - Clemastine
Clemastin Overdose, Contraindications and Information - Clemastine
OVERDOSE
Antihistamine overdosage reactions may vary from central
nervous system depression
to stimulation. In children,
stimulation predominates
initially in a syndrome
which may include excitement, hallucinations, ataxia,
incoordination, muscle twitching, athetosis, hyperthermia,
cyanosis convulsions,
tremors, and hyperreflexia
followed by postictal
depression and cardio-respiratory
arrest. Convulsions in children may be preceded by mild depression.
Dry mouth, fixed dilated pupils, flushing of the face, and fever
are common. In adults, CNS
depression, ranging
from drowsiness to
coma, is more common. The
convulsant dose
of antihistamines lies near the lethal
dose. Convulsions indicate a p.o.
prognosis.
In both children and adults, coma
and cardiovascular
collapse may occur.
Deaths are reported especially in infants and children.
There is no specific
therapy for acute
overdosage with antihistamines. The latent
period from ingestion
to appearance of
toxic effects is characteristically
short (½ - 2 hours). General symptomatic
and supportive measures should be instituted promptly and maintained
for as long as necessary.
Since overdoses of other classes of drugs (i.e. tricyclic antidepressants)
may also present anticholinergic
symptomatology, appropriate
toxicological analysis should be performed as soon as possible to
identify the causative agent.
In the conscious
patient, vomiting
should be induced even
though it may have occurred spontaneously. If vomiting
cannot be induced, gastric
lavage is indicated. Adequate precautions must be taken to protect
against aspiration, especially in infants and children. Charcoal
slurry or other suitable
agents should be instilled into the stomach
after vomiting or lavage.
Saline cathartics or milk
of magnesia may be
of additional benefit. In the unconscious
patient, the airway
should be secured with a cuffed endotracheal t.b.
before attempting to evacuate
the gastric contents.
Intensive supportive and nursing
care is indicated, as for any comatose
patient.
If breathing is significantly
impaired, maintenance of an adequate airway and mechanical support
of respiration is
the most effective means of providing adequate oxygenation.
Hypotension is an early sign
of impending cardiovascular
collapse and should
be treated vigorously. Although general supportive measures are
important, specific
treatment with intravenous
infusion of a vasopressor
titrated to maintain adequate blood
pressure may be necessary.
Do not use with CNS stimulants.
Convulsions should be controlled by careful administration
of diazepam or a short-acting
barbiturate, repeated as necessary. Physostigmine may also be considered
for use in controlling centrally mediated convulsions. Ice packs
and cooling sponge baths,
not alcohol, can aid in
reducing the fever commonly
seen in children. A more detailed review of antihistamine
toxicology and overdose
management is available in Gosselin, RE., et. al., “Clinical Toxicology
of Commercial Products.”
CONTRAINDICATIONS
Antihistamines are contraindicated in patients hypersensitive
to the drug or to other antihistamines of similar chemical
structure (see DRUG
INTERACTIONS).
Antihistamines should not be used in newborn
or premature infants.
Because of the higher risk
of antihistamines for infants generally and for newborns and prematures
in particular, antihistamine
therapy is contraindicated
in nursing mothers (see
PRECAUTIONS: Nursing Mothers).
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