Scopolamine butylbromide, also called hyoscine butylbromide or butylscopolamine bromide, is a quaternary ammonium anticholinergic and antispasmodic medicine. It relaxes smooth muscle in the gastrointestinal, biliary, urinary, and genital tracts, and is commonly used for abdominal cramps and spasmodic pain. Its best-known brand is Buscopan.
Unlike scopolamine hydrobromide, which crosses into the central nervous system and is used for motion sickness, scopolamine butylbromide is poorly absorbed and has limited central effects after oral use. This makes it suitable for targeted treatment of abdominal and pelvic smooth-muscle spasm, while reducing—but not eliminating—the risk of anticholinergic side effects.
Chemical Structure
“Scopolamine butylbromide” is the N-butyl bromide derivative of scopolamine. Its chemical name is (1R,2R,4S,5S,7R)-9-butyl-7-{[(2S)-3-hydroxy-2-phenylpropanoyl]oxy}-9-methyl-3-oxa-9-azatricyclo[3.3.1.0²,⁴]nonan-9-ium bromide.
Its molecular formula is C21H30BrNO4, and its molecular weight is approximately 440.37 g/mol. The CAS number is 149-64-4. The molecule contains a positively charged quaternary ammonium group, which limits passage through the blood-brain barrier and contributes to its predominantly peripheral action.
Scopolamine Butylbromide-Based Medicines
Common products containing this API include:
- Buscopan coated tablets.
- Buscopan IBS Relief 10 mg tablets.
- Buscopan Cramps 10 mg tablets.
- Buscopan 20 mg/mL injectable solution.
- Buscopan Plus tablets, containing hyoscine butylbromide and paracetamol.
- Generic hyoscine butylbromide 10 mg tablets.
- Generic hyoscine butylbromide injection.
- Generic hyoscine butylbromide suppositories.
Product availability and formulations differ by country. Some products have been discontinued in particular markets, and combination products should not be assumed equivalent to single-ingredient Buscopan.
Mechanism of Action
Scopolamine butylbromide blocks muscarinic acetylcholine receptors in smooth muscle. Acetylcholine normally activates parasympathetic pathways that cause contraction of gastrointestinal, biliary, urinary, and uterine smooth muscle. By blocking these receptors, the medicine reduces spasm and cramping pain.
Its quaternary ammonium structure limits central nervous system penetration, so it acts mainly on peripheral smooth muscle rather than in the brain. It also reduces gastrointestinal motility and secretory activity, which can relieve cramps but may slow absorption of other oral medicines.
Pharmacokinetics
Oral scopolamine butylbromide is poorly absorbed from the gastrointestinal tract. Its oral bioavailability is very low—reported as approximately 0.13% when calculated from plasma levels—and systemic exposure is generally minimal.
After oral administration, peak plasma concentrations occur at about two hours and are low even after doses ranging from 20 to 400 mg. Most of an oral dose is eliminated in feces, while only about 2% to 5% of radioactivity is recovered in urine. The full elimination half-life after high oral doses ranges from approximately 6.2 to 10.6 hours.
Therapeutic Uses
| Condition | Role of scopolamine butylbromide |
|---|---|
| Irritable bowel syndrome | Relieves abdominal cramps and discomfort |
| Gastrointestinal spasm | Relaxes intestinal smooth muscle |
| Stomach cramps | Provides short-term symptomatic relief |
| Biliary colic or spasm | May reduce smooth-muscle spasm in selected patients |
| Renal or urinary-tract spasm | Relieves cramping associated with urinary conditions |
| Bladder spasm | Reduces involuntary bladder-muscle contraction |
| Menstrual cramps | Some products, especially combinations, are approved for dysmenorrhea |
| Gastrointestinal imaging | Injectable forms may be used to reduce gut motility and improve visualization |
Buscopan tablets are used for cramps in the stomach, intestines, bladder, and urinary tract, and for symptoms of irritable bowel syndrome. Injectable forms are used in some countries for acute spasm and diagnostic procedures.
Side Effects
Common or notable effects include dry mouth, blurred vision, fast heartbeat, constipation, urinary retention, flushing, sweating changes, and gastrointestinal motility reduction. Dry mouth and tachycardia are listed as uncommon in UK product information, while urinary retention is rare.
Serious reactions are uncommon but can occur. These include allergic reactions, angioedema, skin rash, urticaria, and rarely anaphylaxis or anaphylactic shock. Injectable Buscopan can cause significant tachycardia and hypotension, so it should be administered only in an appropriate clinical setting.
Drug Interactions
Scopolamine butylbromide can intensify the effects of other anticholinergic medicines. These include tricyclic and tetracyclic antidepressants, antihistamines, quinidine, amantadine, antipsychotics, disopyramide, tiotropium, ipratropium, and atropine-like medicines. Combined use may increase dry mouth, blurred vision, constipation, urinary retention, and confusion.
It may also enhance the heart-rate effects of beta-adrenergic medicines, such as salbutamol. Antacids and adsorbent antidiarrheal medicines can reduce absorption of anticholinergics; where possible, scopolamine butylbromide should be taken at least one hour before these products.
Because the medicine slows gastrointestinal motility, it may delay absorption and alter the effect of other oral medicines, particularly those with a narrow therapeutic index. Patients should tell clinicians about all prescription medicines, over-the-counter products, and supplements.
Safety Considerations
Scopolamine butylbromide is contraindicated in people with known hypersensitivity to hyoscine butylbromide or related anticholinergic agents, myasthenia gravis, mechanical gastrointestinal obstruction, paralytic or obstructive ileus, megacolon, or narrow-angle glaucoma. It should also be avoided in significant urinary retention due to prostate enlargement and in certain serious heart-rhythm disorders.
Caution is needed in people with tachycardia, thyrotoxicosis, heart failure, or cardiac disease because the medicine can further increase heart rate. Abdominal pain can also signal a serious condition such as bowel obstruction, appendicitis, or ischemia; the medicine should not be used to mask unexplained or severe abdominal pain.
Pregnancy and breastfeeding guidance differs by country. UK Buscopan labeling advises against use during pregnancy or breastfeeding, while NHS information notes that occasional use during breastfeeding may be acceptable when needed, with other medicines potentially preferred. Patients should follow the local product label and consult a healthcare professional.
Regulatory Status
Scopolamine butylbromide was first registered in Germany in 1951 and marketed in 1952 as Buscopan. It has since become available worldwide as both a prescription medicine and, in many countries, an over-the-counter product.
Regulatory status varies substantially by country and formulation. In the United Kingdom, Buscopan Cramps and IBS Relief products are available for abdominal cramps and IBS symptoms, while injectable Buscopan is prescription-only. In the United States, Buscopan injectable solution has been marketed, but oral Buscopan products are not generally available as FDA-approved human medicines.
Clinical Evidence and Limitations
Clinical evidence supports scopolamine butylbromide for short-term relief of abdominal cramps and spasmodic pain, particularly in irritable bowel syndrome and other functional gastrointestinal conditions. By reducing smooth-muscle contraction, it can ease cramping, discomfort, and pain, allowing people to continue daily activities while the underlying episode settles. However, it treats the symptom of spasm rather than curing the condition causing it.
Evidence is more limited for some uses, such as biliary colic, urinary spasm, and menstrual cramps, and effectiveness may vary between individuals. It should not be used to mask severe, persistent, or unexplained abdominal pain, which may indicate bowel obstruction, appendicitis, gallbladder disease, or another condition requiring urgent assessment. In IBS, it is best used as part of a broader plan that includes diet, stress management, fiber adjustment, and medical review when symptoms persist.
Conclusion
Scopolamine butylbromide is a peripherally acting anticholinergic antispasmodic used to relieve smooth-muscle cramps in the gastrointestinal, urinary, biliary, and reproductive tracts. Its poor oral absorption limits systemic exposure and makes it useful for targeted abdominal symptoms, particularly IBS-related cramping.
Its main risks are anticholinergic effects, including dry mouth, blurred vision, fast heartbeat, constipation, and urinary retention. It must be avoided in bowel obstruction, glaucoma, myasthenia gravis, and other contraindicated conditions. Because product availability and restrictions differ by country, treatment should follow current local labeling and medical advice.
