Hyoscyamine Side Effects

For the Consumer

Applies to hyoscyamine: oral conventional tablets and sublingual tablets, oral extended-release capsules and tablets, oral oral solution and elixir, oral orally disintegrating tablets, parenteral injection

Side effects include:

Most adverse effects are manifestations of pharmacologic effects at muscarinic-cholinergic receptors and usually are reversible when therapy is discontinued.

Severity and frequency of adverse effects are dose related and individual intolerance varies greatly; adverse effects occasionally may be obviated by a reduction in dosage but this also may eliminate potential therapeutic effects.

Adverse effects include dry mouth, urinary hesitancy and retention, blurred vision, tachycardia, palpitations, mydriasis, increased ocular tension, loss of taste, headache, nervousness, drowsiness, weakness, fatigue, dizziness, insomnia, nausea, vomiting, impotence, constipation, bloated feeling, abdominal pain, diarrhea, allergic reactions or drug idiosyncrasies, urticaria and other dermal manifestations, ataxia, speech disturbance, mental confusion and/or excitement (especially in geriatric patients), short-term memory loss, hallucinations, and decreased sweating.

For Healthcare Professionals

Applies to hyoscyamine: compounding powder, injectable solution, oral capsule extended release, oral liquid, oral solution, oral spray, oral tablet, oral tablet chewable, oral tablet disintegrating, oral tablet extended release, sublingual tablet

Cardiovascular

Cardiovascular side effects have included tachycardia, premature ventricular depolarizations, and ventricular tachycardia.^[Ref]

Gastrointestinal

Gastrointestinal side effects due to the anticholinergic effects of hyoscyamine have commonly included dry mouth and mucous membranes. Other reported side effects include delayed gastric emptying time, reduced gastric acid secretion, constipation, and gastroesophageal reflux.^[Ref]

General

Hyoscyamine toxicity (anticholinergic side effects) often presents as fever, tachycardia, agitation, and dry skin/mucous membranes.^[Ref]

Genitourinary

Genitourinary complications include urinary retention (due to anticholinergic effects on the urinary sphincter), which is common and dose-related, and impotence in male patients.^[Ref]

Hypersensitivity

Hypersensitivity reactions to hyoscyamine are rare. Reactions can include urticaria, eczema, papillary hyperplasia, mucopurulent discharge, eosinophilia, pruritus, edema, hypotension, abdominal pain, tachypnea, nausea and vomiting.^[Ref]

Nervous system

Nervous system side effects have included lethargy and somnolence. Higher doses may be associated with mental confusion and/or excitement. The elderly appear to be more prone to the anticholinergic effects of hyoscyamine on the CNS.^[Ref]

Ocular

Ocular side effects due to the anticholinergic activity of hyoscyamine have included inhibition of the iris sphincter muscle (possibly resulting in mydriasis), follicular conjunctivitis, and inhibition of the ciliary muscle (which can produce blurred vision). All muscarinic antagonists can precipitate glaucoma.^[Ref]

Endocrine

Endocrine side effects have included inhibition of exocrine sweat glands. This is usually not clinically significant except when perspiration becomes a major factor in body temperature control.^[Ref]

Not all side effects for hyoscyamine may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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