Side effects are quite common with the use of atropine and its congeners; are due to facets of its action other than for which it is being used. They cause inconvenience but are rarely serious.
SIDE EFFECTS AND TOXICITY
Side effects are quite
common with the use of atropine and its congeners; are due to facets of its
action other than for which it is being used. They cause inconvenience but are
rarely serious.
Belladonna poisoning
may occur due to drug overdose or consumption of seeds and berries of
belladonna/datura plant. Children are highly susceptible. Manifestations are
due to exaggerated pharmacological actions.
Dry mouth, difficulty
in swallowing and talking. Dry, flushed and hot skin (especially over face and
neck), fever, difficulty in micturition, decreased bowel sounds, a scarlet rash
may appear. Dilated pupil, photophobia, blurring of near vision, palpitation.
Excitement, psychotic
behaviour, ataxia, delirium, dreadful visual hallucinations.
Hypotension, weak and
rapid pulse, cardiovascular collapse with respiratory depression.
Convulsions and coma
occur only in severe poisoning.
Diagnosis Methacholine 5 mg or neostigmine 1 mg s.c. fails to induce typical muscarinic
effects.
Treatment If poison has been ingested, gastric lavage should be done with tannic acid (KMnO4
is ineffective in oxidizing atropine). The patient should be kept in a dark
quiet room. Cold sponging or ice bags are applied for reducing body
temperature. Physostigmine 1–3 mg s.c. or i.v. antagonises both central and
peripheral effects, but has been found to produce hypotension and arrhythmias
in some cases. As such, its utility is controversial. Neostigmine does not
antagonise the central effects.
Other
general measures (maintenance of blood volume, assisted respiration, diazepam
to control convulsions) should be taken as appropriate.
Contraindications
Atropinic drugs are absolutely
contraindicated in individuals with a narrow iridocorneal angle—may precipitate
acute congestive glaucoma. However, marked rise in intraocular tension is rare in
patients with wide angle glaucoma.
Caution
is advocated in elderly males with prostatic hypertrophy—urinary retention can
occur.
Interactions
§ Absorption of most
drugs is slowed because atropine delays gastric emptying. This results in
slower absorption and greater peripheral degradation of levodopa—less of it
reaches the brain. This does not occur when a peripheral decarboxylase
inhibitor is combined.
§ On the other hand,
extent of digoxin and tetracycline absorption may be increased due to longer
transit time in the g.i.t.
§ Antacids interfere
with absorption of anticholinergics.
§ Antihistaminics, tricyclic
antidepressants, phenothiazines, disopyramide, pethidine
§ have anticholinergic
property—additive side effects occur with atropinic drugs.
§ MAO inhibitors
interfere with metabolism of anticholinergic antiparkinsonian drugs — delirium
may occur.
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