Hyoscyamine
Pronunciation: hy-oh-SYE-a-meen.
- Generic name
- hyoscyamine sulfate
- Drug class
- Anticholinergic (antimuscarinic) / antispasmodic
- Form
- Tablet, sublingual tablet, or orally disintegrating tablet, typically 0.125 mg
- Route
- Oral (tablet, sublingual tablet, or orally disintegrating tablet)
- Legal status
- Prescription-only in the United States and Canada; note: current US labeling states the FDA has not approved this specific product's labeling (see regulatory note below)
Availability and supply rules vary by country
Trade names by country: United States · Canada · Australia
Australia: Donnatab (combination with atropine sulfate and hyoscine hydrobromide) (3) · Full directory
What hyoscyamine sulfate is and how it works
Hyoscyamine is an anticholinergic (antispasmodic) medicine used to reduce muscle spasm and excess secretions in conditions such as irritable bowel syndrome, bladder spasm, and certain stomach/gut disorders. Its current US labeling has not gone through a modern FDA drug-approval review, though it remains a genuine, widely available prescription medicine. (1)
Take hyoscyamine exactly as your prescriber or pharmacist directs. Do not exceed the maximum daily amount stated on your label, and tell your prescriber about any eye, bladder, bowel, or heart conditions before starting, since this medicine is contraindicated in several specific conditions.
Mechanism of action: how hyoscyamine sulfate works
Hyoscyamine is the pharmacologically active levorotatory isomer of atropine, a competitive antagonist at muscarinic acetylcholine receptors. It reduces smooth-muscle tone and motility in the GI and urinary tracts and reduces glandular (salivary, gastric, sweat) secretions. (1)
What hyoscyamine sulfate is used for
Irritable bowel syndrome and functional GI spasm
Used to help relieve cramping, spasm, and excess secretions associated with irritable bowel syndrome and other functional gastrointestinal disorders, and as adjunctive therapy for peptic ulcer disease. (1)
Bladder spasm and related urinary conditions
Used to help relieve spasm and irritability of the bladder, including in cystitis and neurogenic bladder disturbances. (1)
Other spasm-related and secretory conditions
Also used adjunctively (with narcotic pain medicine) for biliary and renal colic pain, for parkinsonism-related rigidity, and to reduce excess nasal secretions (rhinorrhoea) in acute rhinitis. (1)
Before taking hyoscyamine sulfate
Do not take / not appropriate for
- Do not take hyoscyamine if you have glaucoma. (all countries) (1)
- Do not take hyoscyamine if you have myasthenia gravis. (all countries) (1)
- Do not take hyoscyamine if you have a blockage of the urinary tract (for example from prostate enlargement) or a blockage or narrowing of the gastrointestinal tract, or paralytic ileus (a stalled bowel), or intestinal atony, particularly if you are elderly or debilitated. (all countries) (1)
- Do not take hyoscyamine if you have unstable heart/circulation status during acute bleeding, severe ulcerative colitis, or toxic megacolon. (all countries) (1)
Tell your clinician about
- Any history of glaucoma, myasthenia gravis, prostate enlargement, or bowel obstruction.
- Any heart disease, especially if unstable or with recent bleeding.
- Kidney, liver, or heart problems, which can increase your risk of side effects.
- Whether you are pregnant, planning pregnancy, or breastfeeding.
- All other medicines you take, especially other anticholinergic medicines, antidepressants, or antacids.
How to take hyoscyamine sulfate
- Take by mouth as directed by your prescriber or pharmacist, generally every 4 hours or as needed.
- Do not exceed the maximum daily amount stated on your product label or by your prescriber.
- If you also take antacids, take hyoscyamine before meals and the antacid afterward, since antacids can reduce how well hyoscyamine is absorbed.
- This medicine can cause drowsiness, dizziness, or blurred vision -- avoid driving or operating machinery until you know how it affects you.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3)
Missed dose
This medicine is often taken as needed rather than on a fixed schedule. If you take it on a fixed schedule and miss a dose, take it when you remember unless it is nearly time for your next dose -- do not double up. Ask your prescriber or pharmacist if you are unsure.
Overdose
Seek urgent medical attention if too much has been taken, especially with symptoms such as severe confusion, hallucinations, a very fast heartbeat, difficulty urinating, or very high body temperature. (1)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms.
Dry mouth.
What to notice: Dry mouth.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Blurred vision and dilated pupils.
What to notice: Blurred vision and dilated pupils.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Difficulty urinating or urinary retention.
What to notice: Difficulty urinating or urinary retention.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Constipation, nausea, or vomiting.
What to notice: Constipation, nausea, or vomiting.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Drowsiness, dizziness, or headache.
What to notice: Drowsiness, dizziness, or headache.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Rapid heartbeat or palpitations.
What to notice: Rapid heartbeat or palpitations.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)
Serious warnings
Signs of heat prostration (overheating) — high caution
Symptoms: Fever, hot and flushed skin, or heat-related illness, especially in hot weather or with strenuous activity -- this medicine reduces sweating.
Action: Avoid excessive heat and exertion, and seek prompt medical attention for suspected heat illness. (1)
Confusion, hallucinations, or unusual behaviour (especially in older adults) — high caution
Symptoms: New confusion, agitation, hallucinations, or disorientation after starting or increasing the dose.
Action: Contact your prescriber promptly. These effects usually resolve within 12-48 hours of a clinician-directed adjustment, but should always be reported rather than managed alone. (1)
Diarrhoea as a possible sign of incomplete bowel obstruction — high caution
Symptoms: New or worsening diarrhoea, especially if you have an ileostomy or colostomy.
Action: Contact your prescriber promptly, as this can be an early sign of bowel obstruction rather than ordinary diarrhoea. (1)
Severe urinary retention or eye pain — emergency
Symptoms: Inability to urinate, or sudden eye pain with visual disturbance (a possible sign of a narrow-angle glaucoma emergency).
Action: Seek emergency medical care immediately. (1)
Interactions
- Other anticholinergic medicines, tricyclic antidepressants, MAO inhibitors, phenothiazines, haloperidol, and amantadine can add to hyoscyamine's anticholinergic effects (dry mouth, blurred vision, confusion, urinary retention). (1)
- Antacids can reduce how well hyoscyamine is absorbed -- take hyoscyamine before meals and any antacid afterward if both are used. (1)
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
No formal animal reproduction studies have been performed. This medicine should be used in pregnancy only if clearly needed, as judged by your prescriber. (1) (2) (3)
Breastfeeding
Hyoscyamine passes into breast milk. Use with caution while breastfeeding, and discuss with your prescriber. (1) (2) (3)
Children
Used in children 2 years and older for certain conditions, at lower weight-based doses than adults, under a prescriber's direction. (1) (2) (3)
Elderly
Older adults are more susceptible to confusion, hallucinations, and other anticholinergic effects, and to reduced kidney clearance of the drug -- lower starting doses and closer monitoring are prudent. (1) (2) (3)
Hepatic_impairment
Increased risk of side effects with liver problems -- discuss with your prescriber. (1) (2) (3)
Renal_impairment
This medicine is substantially cleared by the kidneys, so reduced kidney function increases the risk of side effects -- your prescriber may use a lower dose. (1) (2) (3)
Source_ids
Monitoring
Before starting
- Screening for glaucoma, myasthenia gravis, urinary or GI obstruction, and cardiovascular stability
During treatment
- Watching for anticholinergic side effects such as urinary retention, constipation, or confusion, especially in older adults.
- Watching for diarrhoea that could indicate incomplete bowel obstruction rather than ordinary GI upset.
- Monitoring kidney function where relevant.
Storage
Store at controlled room temperature, 20-25°C (68-77°F); brief excursions between 15-30°C (59-86°F) are permitted. Keep in a tight, light-resistant container with a child-resistant closure, out of reach of children.
Professional information
Clinician-facing context only, sourced from current US marketed labeling (not an FDA-approved label -- see regulatory status note) and Health Canada/TGA sources; verify against current local prescribing information.
United States
Indication: GI/bladder spasm, adjunctive peptic ulcer therapy, and related conditions (as marketed, not FDA-approved labeling)
Dose summary: Adults and children 12+: 0.125-0.25 mg every 4 hours or as needed, max 1.5 mg/24h. Children 2 to <12: half to 1 tablet (approx. 0.0625-0.125 mg) every 4 hours or as needed, max 6 tablets/24h, weight-based.
Renal context: Substantial renal elimination; use lower doses and monitor in renal impairment. (1)
Hepatic guidance
Increased risk of adverse effects with hepatic impairment; use with caution.
Overdose note
Overdose produces an anticholinergic toxidrome: dry flushed skin, hyperthermia, tachycardia, mydriasis, urinary retention, agitation, delirium, and possibly seizures or coma in severe cases; manage supportively with continuous cardiac and temperature monitoring. (1)
Frequently asked questions
Is hyoscyamine an FDA-approved medicine?
Hyoscyamine sulfate products such as Levsin have a long marketing history in the United States under a grandfathered ('DESI') framework rather than a modern FDA drug-approval review. Current labeling states the FDA has not found the drug safe and effective and has not approved that specific labeling. It remains a genuine, prescription-only medicine that is widely dispensed in US pharmacies, but this regulatory nuance is worth knowing. (1)
Is hyoscyamine the same as hyoscine (scopolamine) or hyoscine butylbromide (Buscopan)?
No. Hyoscyamine, hyoscine (scopolamine), and hyoscine butylbromide are related belladonna-alkaloid anticholinergic medicines but are chemically and clinically distinct, with different approved uses and regulatory status in different countries. (1)
Is hyoscyamine available in the UK, Europe, Australia, and New Zealand?
Its availability outside North America is limited and uneven: in Australia it is only found as an ingredient in a combination product (Donnatab), and no standalone licensed hyoscyamine product could be confirmed in the United Kingdom, European Union, or New Zealand at the time of this review. It is confirmed available in the United States and Canada. (1) (2) (3)
What is the mechanism of action of hyoscyamine sulfate?
Hyoscyamine is the pharmacologically active levorotatory isomer of atropine, a competitive antagonist at muscarinic acetylcholine receptors. It reduces smooth-muscle tone and motility in the GI and urinary tracts and reduces glandular (salivary, gastric, sweat) secretions. (1)
What is the generic name of Hyoscyamine?
The generic name is hyoscyamine sulfate. (1)
What class of drug is hyoscyamine sulfate?
Hyoscyamine is classed as: Anticholinergic (antimuscarinic) / antispasmodic. (1)
References
- LEVSIN (hyoscyamine sulfate) tablets -- current DailyMed labelingU.S. Food and Drug Administration / DailyMed (NIH), current marketed labeling, Viatris Specialty LLC · United States · accessed 2026-07-30 · source 1
- Hyoscyamine sulfate -- Health Canada Drug Product Database listingHealth Canada Drug Product Database (DPD) · Canada · accessed 2026-07-30 · source 2
- DONNATAB tablet (hyoscyamine sulfate dihydrate + atropine sulfate monohydrate + hyoscine hydrobromide) -- ARTG registrationTherapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-30 · source 3
Brand names by country
Single-ingredient hyoscyamine sulfate names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- Hyoscyamine Sulfate TAB.125 mg · bryant ranch prepack
- Hyoscyamine Sulfate SL.125 mg · acella pharmaceuticals, llc
- Hyosyne.125 mg/5mL, .125 mg/mL · atlantic biologicals corp.
- Hyoscyamine sulfate Sublingual.125 mg · chartwell rx, llc
- OSCIMIN.125 mg · larken laboratories, inc.
- Levsin.125 mg · viatris specialty llc
- Levbid.375 mg · viatris specialty llc
- Digenyx.125 mg · puretek corporation
- NuLev.125 mg · viatris specialty llc
- Levsin SL.125 mg · viatris specialty llc
Canada
- Hyoscyamine sulfate (generic) (2)Health Canada DPD listed confirmed · not specified in fetched source · various
Australia
- Donnatab (combination with atropine sulfate and hyoscine hydrobromide) (3)TGA ARTG registered 1997-07-08 confirmed combination product only · not specified in fetched source · Haleon Australia Pty Ltd