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Hyoscine butylbromide (butylscopolamine), the sole drug in ATC class A03BB01, is a peripherally acting antispasmodic with a relatively favourable toxicological profile and appears compatible with breastfeeding when used short term and at therapeutic doses, with infant and milk supply monitoring.medpedia.framar+5

Active substance and indications

Hyoscine butylbromide (also called butylscopolamine or scopolamine butylbromide) is a semisynthetic quaternary ammonium derivative of belladonna alkaloids, classified in ATC A03BB01 “belladonna alkaloids, semisynthetic, quaternary ammonium compounds”.atcddd.fhi+2
It is used as an antispasmodic for smooth muscle spasm in the gastrointestinal tract, biliary tract and genitourinary system, including abdominal cramping, biliary and renal colic, and adjunctively in diagnostic procedures.medicalguidelines.msf+3

Mechanism of action and pharmacology

Hyoscine butylbromide is a competitive antagonist at peripheral muscarinic receptors, exerting anticholinergic (M‑holinolytic) effects on gastrointestinal, biliary and urinary smooth muscle, thereby reducing spasm and pain.pubmed.ncbi.nlm.nih+2
Because it is a quaternary ammonium compound, it has low lipid solubility, poor oral absorption and does not significantly cross the blood–brain barrier, so central anticholinergic effects are minimal compared with tertiary amines such as atropine.wikipedia+2

Dosage and administration

Oral formulations (commonly 10 mg tablets) are given in adults and adolescents ≥12 years at doses of 10–20 mg (1–2 tablets) up to 3–4 times daily, with a typical maximum daily dose around 80 mg.hpra+2
Parenteral preparations (e.g. 20 mg/ml injection) are used in acute spasm and radiological procedures, usually 20 mg intravenously or intramuscularly, repeatable after 30 minutes if needed, with a maximum daily dose around 100 mg.medicines+2

General toxicity and overdose

Hyoscine butylbromide has a relatively low acute toxicity; reported oral LD50 values in animals are in the gram‑per‑kilogram range, reflecting a wide safety margin.medsafe
Overdose produces atropine‑like anticholinergic toxicity, including tachycardia, dry mouth, accommodation disorders, urinary retention, decreased gastrointestinal motility, flushing and potential circulatory collapse, managed with gastric decontamination, supportive care and, if required, parenteral cholinesterase inhibitors such as neostigmine.medpedia.framar+2

Contraindications and precautions

Contraindications include known hypersensitivity, myasthenia gravis, mechanical intestinal obstruction, pyloric stenosis, toxic megacolon, narrow‑angle glaucoma and prostatic hypertrophy with urinary retention risk.hpra+2
Caution is advised in patients with tachyarrhythmias, coronary heart disease, fever (due to impaired thermoregulation) and in those at risk of urinary retention, with avoidance of prolonged use without etiological clarification of pain.medicalguidelines.msf+2

Adverse effects and drug interactions

The typical adverse reaction profile reflects peripheral anticholinergic activity: tachycardia, palpitations, increased intraocular pressure, mydriasis and vision disturbances, dry mouth, decreased bronchial secretions, constipation, urinary hesitancy or retention, reduced sweating with possible heat intolerance, and occasionally skin reactions such as rash or urticaria.medicines+3
Serious reactions are uncommon at therapeutic doses; no clinically relevant CYP‑mediated interactions are known, and the drug is considered probably non‑porphyrinogenic, with uneventful use reported in patients with acute porphyria.drugsporphyria+1

Lactation pharmacokinetics and transfer into milk

Orally administered hyoscine butylbromide is poorly absorbed, with only about 8–10% reaching systemic circulation, which limits the amount potentially available for transfer into breast milk.droracle+2
There are no direct human quantitative data on milk concentrations, but given its quaternary structure, low bioavailability and poor oral absorption in the infant, any ingested amount from milk is expected to have minimal systemic effect on the breastfed child.infantrisk+3

Evidence and recommendations in breastfeeding

Several expert resources state that hyoscine butylbromide can be used during breastfeeding, with preference among gastrointestinal antispasmodics when treatment is necessary and limited in duration.sps+2
Some product information and regulatory documents remain cautious, advising that use during breastfeeding is not routinely recommended or that a risk to the breastfed child cannot be excluded, reflecting lack of formal studies rather than documented harm.medsafe+2

Potential effects on the breastfed infant

Based on pharmacology, clinically relevant exposure of the infant via breast milk is unlikely, but theoretical anticholinergic effects (constipation, urinary retention, dry mouth, decreased sweating) could occur with high maternal doses, parenteral use or prolonged therapy, especially in neonates and young infants.gpnotebook+2
Available case‑based and expert opinion sources have not identified confirmed adverse events in breastfed infants attributable to hyoscine butylbromide, yet they recommend clinical vigilance for feeding difficulties, poor weight gain, changes in stooling and signs of dehydration.droracle+3

Potential effects on lactation and milk production

Antimuscarinic agents may theoretically suppress breast milk production by inhibiting parasympathetic pathways involved in lactation, although this effect is more clearly described for high systemic exposures and centrally acting compounds.sps+1
In practice, once lactation is well established, short‑term use of hyoscine butylbromide at standard doses is unlikely to significantly reduce milk volume, but prolonged or high‑dose use may warrant monitoring of maternal milk supply and consideration of alternatives in women with borderline production.gpnotebook+2

Clinical use during breastfeeding: risk–benefit assessment

For otherwise healthy breastfeeding mothers with acute gastrointestinal or biliary spasm, short‑term use of oral hyoscine butylbromide in standard doses is generally acceptable when non‑pharmacological measures are insufficient, provided that maternal and infant monitoring is ensured.medpedia.framar+3
In neonates, preterm infants or when repeated high parenteral doses are anticipated, clinicians should individualise therapy, consider alternative antispasmodics with more lactation‑specific data, and use the lowest effective dose for the shortest possible duration.sps+2

Practical lactation‑toxicity guidance for healthcare professionals

When prescribing hyoscine butylbromide to a breastfeeding woman, document indication, planned duration and dosing, and counsel on potential anticholinergic maternal side effects and warning signs in the infant.hpra+3
Advise mothers to seek medical review if the child develops reduced feeding, unusual somnolence or irritability, constipation, decreased urine output, or signs of overheating, and to avoid concurrent use of other anticholinergic medications without professional supervision.infantrisk+2

Summary for toxicology–lactology practice

Hyoscine butylbromide (A03BB01) is a peripherally acting antimuscarinic antispasmodic with a wide therapeutic index and predictable atropine‑like toxicity in overdose, requiring standard decontamination and supportive measures.pubmed.ncbi.nlm.nih+3
While robust lactation pharmacokinetic data are lacking, its poor systemic absorption, quaternary structure and clinical experience support cautious but generally favourable use in breastfeeding, especially for short courses, with emphasis on patient‑specific risk–benefit assessment and clinical monitoring of both mother and child.nhs+5