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Cyclobutyrol (ATC A05AX03) is a choleretic drug used in bile therapy that reduces biliary lipid secretion; there are no specific, evidence‑based lactation safety data, so risk assessment in breastfeeding must be individualized and cautious.medpedia.framar+6

Overview and ATC context

Cyclobutyrol belongs to the ATC class A05AX03, within “Other drugs for bile therapy” (A05AX) in the broader group “Bile and liver therapy” (A05). It is indicated for bile therapy and is used in the management of biliary tract disorders as a choleretic agent that modulates bile composition. The drug is generally reserved for specialist use and is not widely represented in current clinical guidelines, which limits direct clinical lactation data.wikipedia+8

Pharmacological class

• ATC code: A05AX03 – cyclobutyrol.atcddd.fhi+2
• Group: A – Alimentary tract and metabolism; A05 – bile and liver therapy; A05A – bile therapy; A05AX – other bile therapy drugs.ebi+3
• Therapeutic category: Choleretic agent used in bile therapy, influencing biliary lipid secretion while maintaining bile acid flow.drugs.ncats+3

Pharmacodynamics and pharmacokinetics

Cyclobutyrol is described as a choleretic drug that stimulates bile flow yet selectively reduces biliary cholesterol and phospholipid secretion without significantly affecting bile acid secretion. In perfused rat liver models, administration of cyclobutyrol rapidly decreases biliary outputs of cholesterol and phospholipid across a range of bile acid infusion rates, suggesting an action at the canalicular membrane level on lipid transport. The clinical rationale is to improve biliary drainage while lowering the concentration of lithogenic lipids, which may be beneficial in certain cholestatic or biliary conditions.pubmed.ncbi.nlm.nih+4

Human pharmacokinetic data for cyclobutyrol (absorption, distribution, protein binding, metabolism and elimination) are not well characterized in currently accessible sources. Based on general principles of lactation pharmacology, properties such as high plasma protein binding, lower lipid solubility and short elimination half‑life would be expected to limit transfer into breast milk, but these parameters are not specifically reported for this drug.fpnotebook+4

Clinical use and general safety

Cyclobutyrol is used in bile therapy as an adjunctive treatment for disorders of the biliary tract, aiming to modify bile composition and reduce biliary lipid secretion. It is typically used under specialist supervision because of limited modern clinical data and its niche indication profile. The Bulgarian source explicitly notes its use “в жлъчната терапия” (in bile therapy), which is consistent with the international description.medbox.iiab+4

Contraindications and precautions

The Bulgarian monograph lists hypersensitivity to cyclobutyrol or any excipients as a contraindication, and this remains a standard safety restriction. General precautions for bile‑therapy drugs include monitoring for gastrointestinal symptoms, liver function changes and potential alterations in biliary dynamics, although these are extrapolated from class effects rather than cyclobutyrol‑specific controlled trials. In clinical practice, cyclobutyrol would be avoided in patients with documented allergy, severe uncontrolled hepatic impairment or in situations where modulation of bile flow and composition could be harmful.medpedia.framar+3

Toxicological profile

Published toxicological data for cyclobutyrol are sparse, and modern high‑quality safety studies are limited. Preclinical work in isolated perfused rat liver primarily focuses on its effect on biliary secretion rather than systemic toxicity, showing targeted inhibition of biliary lipids with preserved bile acid output. There is no accessible evidence of specific organ toxicity at therapeutic doses, but the lack of comprehensive toxicology necessitates a conservative risk assessment, particularly in vulnerable populations such as pregnant or lactating women.samples.jblearning+4

From a toxicological–lactological standpoint, the main concern is potential exposure of the breastfed infant to a drug that alters bile composition and might affect hepatic or biliary physiology, especially in neonates and preterm infants who have immature hepatic function. In the absence of infant exposure studies, cyclobutyrol should not be considered a low‑risk, routine choice during breastfeeding.mayoclinic+2

Lactation safety assessment

Evidence base

No dedicated lactation monograph or human breast‑milk studies for cyclobutyrol are available in major lactation resources (e.g. LactMed or standard lactation pharmacology texts). General breastfeeding medication guidance emphasizes that most medicines transfer into breast milk to some degree, but infant exposure is usually low and rarely clinically significant. However, exceptions exist, and caution is advised for drugs with limited safety data, drugs that affect liver, bile acids or lipid metabolism, or drugs used systemically in newborns and preterm infants.ncbi.nlm.nih+1youtubefpnotebook+2

Theoretical risk factors

• Unknown milk transfer: There are no data describing cyclobutyrol concentrations in human milk or infant plasma.ncbi.nlm.nih+1
• Potential hepatic and biliary effects in infants: Because cyclobutyrol modulates biliary lipid secretion, any exposure in infants with immature hepatobiliary systems could theoretically influence bile composition or cholesterol handling.pubmed.ncbi.nlm.nih+2
• Lack of post‑marketing lactation safety surveillance: No case series or pharmacovigilance reports on breastfeeding mothers using cyclobutyrol were identified in accessible databases.drugs.ncats+2

Given these factors, cyclobutyrol would be classified pragmatically as a drug with insufficient data for routine use in breastfeeding, and alternative, better‑studied therapies should generally be preferred when treating bile or liver conditions in lactating women.kellymom+3

Practical recommendations in breastfeeding

Based on general lactation pharmacology principles and the absence of specific data, the following pragmatic approach can be suggested for healthcare professionals:

• Avoid cyclobutyrol in breastfeeding when a clinically effective, lactation‑compatible alternative bile‑therapy or hepatobiliary drug is available.kellymom+3
• If cyclobutyrol use is considered essential (e.g. no suitable alternatives, significant maternal benefit), perform an individualized benefit–risk analysis, taking into account maternal disease severity and infant age and health status.fpnotebook+4
• Prefer use in mothers of older, full‑term, healthy infants rather than in preterm or newborn infants, where hepatobiliary vulnerability is greatest.samples.jblearning+2
• Use the lowest effective dose for the shortest duration, and time dosing immediately after breastfeeding or before the infant’s longest sleep interval to reduce peak milk concentrations, following general lactation safety strategies.fpnotebook+2
• Monitor the breastfed infant for changes in feeding behavior, jaundice, stool color or consistency, lethargy or poor weight gain, and seek pediatric evaluation if any concerning signs appear.mayoclinic+2
• Consult specialized lactation pharmacology resources (e.g. LactMed, national medicines information services) for up‑to‑date guidance and potential case data if available.youtubencbi.nlm.nih+1

In summary, cyclobutyrol during lactation is a data‑poor situation; default practice should be to prefer drugs with established breastfeeding safety profiles and reserve cyclobutyrol for carefully selected cases under specialist supervision.ncbi.nlm.nih+3

Web‑page style monograph content

Below is the monograph formatted as concise web‑page content in English, suitable for integration into your toxicological–lactological database.

Title

Cyclobutyrol (ATC A05AX03) – Bile therapy and lactation safety profile

Introduction

Cyclobutyrol is a choleretic drug classified under ATC A05AX03 within the group of “Other drugs for bile therapy.” It is used in bile therapy to modulate biliary secretion, with limited modern clinical and lactation safety data.atccode+3

Indications and therapeutic use

Cyclobutyrol is indicated as an adjunctive agent in bile therapy for selected biliary tract disorders, where modification of bile flow and composition is clinically desired. Its role is mainly specialist‑driven, and it is not commonly featured in contemporary therapeutic guidelines for hepatobiliary diseases.wikipedia+3

Mechanism of action and pharmacodynamics

Cyclobutyrol acts as a choleretic agent, promoting bile secretion while selectively inhibiting biliary lipid output. Experimental data in perfused rat liver demonstrate a reduction in biliary cholesterol and phospholipid secretion across varying bile acid infusion rates, with preservation of bile acid flow, suggesting a primary effect at the canalicular membrane on lipid transport processes. This pharmacodynamic profile may be clinically useful in conditions associated with lithogenic bile or dysregulated biliary lipid composition.medbox.iiab+4

Pharmacokinetics

Human pharmacokinetic parameters (oral bioavailability, plasma protein binding, distribution, metabolism and elimination) for cyclobutyrol are not comprehensively reported in standard reference sources. In the absence of detailed data, lactation risk assessments must rely on general principles of drug transfer into breast milk and on the pharmacodynamic profile rather than on quantitative exposure estimates.drugbank+6

Contraindications and precautions

Cyclobutyrol is contraindicated in patients with known hypersensitivity to the active substance or any excipients. Caution is advised in patients with significant hepatic impairment, obstructive biliary disease or other conditions in which changes in bile flow or composition could be deleterious. Clinicians should consider overall hepatobiliary risk, concomitant medications and the availability of alternative therapies before initiating treatment.medpedia.framar+2

Adverse effects

Specific, systematically collected adverse‑event data for cyclobutyrol are limited. By analogy with other choleretic and bile‑therapy agents, potential adverse effects may include gastrointestinal discomfort, altered stool characteristics and biochemical changes in liver function tests, although these are not firmly documented for cyclobutyrol itself. Pharmacovigilance data do not currently highlight a distinct toxicity pattern, but under‑reporting cannot be excluded.ebi+2

Toxicity and special populations

Robust toxicological datasets for cyclobutyrol, including reproductive and developmental toxicity, are not readily available. In the context of lactation, the absence of infant exposure studies or maternal treatment case series means that safety in breastfeeding cannot be assumed. Special caution is warranted in neonates, preterm infants and infants with underlying hepatobiliary disease if maternal cyclobutyrol therapy is considered.ebi+5

Use during lactation

There are no specific studies of cyclobutyrol use in breastfeeding women, and the drug is not individually profiled in major lactation databases. General principles of lactation pharmacology advise that:youtubesamples.jblearning+1

• Medications with limited safety data and potential hepatic or biliary effects should be used cautiously or avoided in breastfeeding when effective, better‑studied alternatives exist.kellymom+4
• Premature and newborn infants are at highest risk from drug exposure via breast milk; extra caution is necessary in these groups.samples.jblearning+2

In the absence of specific evidence, cyclobutyrol should not be considered a first‑line bile‑therapy option for breastfeeding mothers. Where maternal clinical benefit is judged to outweigh theoretical infant risk, therapy should be individualized, using the lowest effective dose, limiting treatment duration, timing doses around breastfeeding sessions and closely monitoring the infant for signs of hepatic or biliary dysfunction. Consultation with specialist resources (LactMed, national medicines information centers) is recommended for case‑by‑case decisions.mayoclinicyoutubefpnotebook+3