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Other Antiobesity Drugs (ATC A08AX) During Lactation

A08AX is a residual ATC subgroup for other anti-obesity drugs that do not fit the centrally acting stimulant or peripherally acting lipase-inhibitor categories. It is not a pharmacologically uniform drug class; therefore, breastfeeding safety cannot be assigned to the subgroup as a whole and must be assessed for the specific medicine, formulation, dose, indication, maternal condition, and infant characteristics.atcddd.fhi+1

ATC class and general pharmacology

ATC code: A08AX
ATC group: A08A — Antiobesity preparations, excluding diet products
ATC subgroup: A08AX — Other antiobesity drugs.atcddd.fhi+1

A08AX is an administrative and therapeutic classification category rather than a single mechanistic pharmacological class. It is used for anti-obesity medicines that are not classified as centrally acting anti-obesity products under A08AA or as peripherally acting anti-obesity products under A08AB. Consequently, medicines placed in this subgroup may differ substantially in molecular structure, receptor activity, pharmacokinetics, systemic exposure, adverse-effect profile, regulatory status, and clinical relevance during lactation.

The currently identifiable A08AX entry in the WHO ATC/DDD Index is rimonabant (A08AX01), a medicine historically used for weight management through modulation of the endocannabinoid system. Its inclusion illustrates the heterogeneous nature of A08AX. Rimonabant is not representative of every anti-obesity medicine that may be encountered in contemporary clinical practice.atcddd.fhi+1

Importantly, several widely used modern incretin-based medicines prescribed for obesity are not classified in A08AX by the WHO ATC system. Liraglutide, semaglutide, and tirzepatide used for anti-obesity purposes remain classified in the glucose-lowering-drug group A10B, rather than being reclassified under A08AX. This distinction is essential for correct website architecture, drug indexing, and interpretation of ATC-based lactation content.atcddd.fhi+2

At the class level, anti-obesity treatments may reduce body weight through one or more broad mechanisms:

• Alteration of appetite, reward processing, satiety, or central energy-balance pathways.
• Modulation of neuroendocrine signals that influence food intake and energy expenditure.
• Effects on nutrient absorption, gastrointestinal motility, or postprandial metabolic signalling.
• Changes in reward-associated eating behaviour or compulsive food intake.
• Indirect effects on caloric intake through adverse gastrointestinal or neuropsychiatric effects.

Because A08AX is heterogeneous, these mechanisms should not be attributed to every medicine in the subgroup. Each substance requires its own pharmacological monograph and evidence-based lactation assessment.

Toxicological profile

No unified toxicological profile applies to all A08AX medicines. The toxicology of an individual agent depends on its molecular target, receptor selectivity, central nervous system penetration, half-life, active metabolites, degree of maternal systemic exposure, dose-response relationship, co-medications, and the patient’s comorbidities.

At a general level, anti-obesity medicines in this category may produce one or more of the following clinically relevant types of toxicity:

• Neuropsychiatric toxicity, including anxiety, agitation, insomnia, depression, mood instability, altered cognition, or suicidal ideation, depending on the medicine and its central nervous system activity.
• Cardiovascular toxicity, including tachycardia, blood-pressure changes, arrhythmia, ischemic events, or worsening of pre-existing cardiovascular disease.
• Gastrointestinal toxicity, such as nausea, vomiting, abdominal pain, diarrhoea, constipation, reduced appetite, dehydration, or clinically meaningful reduction in nutritional intake.
• Metabolic and nutritional toxicity, including rapid weight loss, inadequate energy intake, micronutrient deficiency, dehydration, and deterioration of nutritional reserves.
• Hepatic, renal, pancreatic, or biliary toxicity, which may arise with particular molecules or in association with profound weight loss, vomiting, dehydration, or drug-specific adverse reactions.
• Drug-interaction toxicity, especially with medicines affecting central neurotransmission, blood pressure, heart rate, glycaemic control, gastric emptying, or absorption of oral medicines.

For the historical A08AX medicine rimonabant, the principal regulatory concern was psychiatric toxicity. It was withdrawn or had its marketing authorization suspended in many jurisdictions because the risk of psychiatric adverse effects—including depression, anxiety, and suicidality—outweighed its clinical benefits. This example reinforces why a broad anti-obesity ATC category must not be assumed to be low risk simply because it is not classified as a classic stimulant group.atcddd.fhi+1

During lactation, maternal toxicity is directly relevant to infant safety. Significant insomnia, mood deterioration, vomiting, diarrhoea, dehydration, dietary restriction, or severe adverse effects may reduce breastfeeding frequency, disrupt milk removal, worsen maternal–infant interaction, impair safe infant care, or necessitate urgent medical treatment.

Lactation pharmacology and infant exposure

A class-wide estimate of drug transfer into human milk cannot be made for A08AX. Different substances within the subgroup may vary greatly in molecular weight, protein binding, lipophilicity, ionization, oral bioavailability, distribution volume, elimination half-life, active-metabolite formation, and oral absorption by the infant.

Accordingly, no universal relative infant dose, milk-to-plasma ratio, infant serum concentration, or breastfeeding compatibility designation exists for A08AX as a whole. These measurements must be determined separately for each active substance. LactMed and related specialist medicines-in-lactation resources are designed to evaluate precisely these substance-specific variables: drug levels in milk and infant blood, possible effects in breastfed infants, effects on lactation, and potential therapeutic alternatives.datadiscovery.nlm.nih+2

General principles relevant to a substance-specific assessment include:

• A medicine with extensive maternal systemic exposure, low molecular weight, long half-life, low protein binding, high lipid solubility, active metabolites, and good oral infant bioavailability may be more likely to produce clinically meaningful infant exposure.
• Large peptide medicines may theoretically have low transfer into milk and may be degraded in the infant gastrointestinal tract, but direct evidence is still needed before compatibility is presumed.
• Medicines with central nervous system activity require additional caution because even low infant exposure may potentially affect sleep, feeding, arousal, behaviour, neurological development, or autonomic regulation.
• Infant vulnerability is highest in neonates, preterm infants, low-birth-weight infants, exclusively breastfed infants, and infants with hepatic, renal, neurological, cardiovascular, or gastrointestinal disease.
• Potential effects on milk production may arise indirectly through maternal weight loss, reduced food intake, dehydration, vomiting, diarrhoea, disturbed sleep, psychiatric symptoms, or altered prolactin-related physiology.

Evidence remains incomplete for many newer anti-obesity medicines in lactation. A 2026 research initiative highlighted the lack of comprehensive human data on anti-obesity medicines and breastfeeding, noting that preliminary findings for one GLP-1-related medicine did not establish broader safety, effects on milk composition, or infant growth and developmental outcomes.gerberfoundation

Therefore, lack of reported harm should not be interpreted as confirmation of safety. Conversely, lack of human milk data does not automatically require cessation of breastfeeding in every clinical situation. Clinical decisions should balance the known or expected maternal benefit, pharmacological properties, quality of available lactation evidence, the feasibility of alternatives, and the individual infant’s vulnerability.

Lactological safety assessment and clinical recommendations

Overall lactological assessment: No class-wide compatibility designation is appropriate; evaluate each active substance individually.

A08AX should not be treated as a single lactation-risk category. The subgroup includes pharmacologically diverse therapies, and the WHO classification itself places some major contemporary anti-obesity medicines, including liraglutide, semaglutide, and tirzepatide, outside A08AX in A10B. Therefore, a clinically meaningful lactological assessment must begin with correct identification of the active ingredient rather than the broad ATC subgroup alone.atcddd.fhi+2

Clinical recommendations

1. Identify the precise medicine before counselling.
   Confirm the generic name, brand name, strength, formulation, dose, dosing interval, route, indication, start date, duration of use, and the date and time of the last dose. For combination, compounded, imported, or online products, identify every listed ingredient and consider the possibility of undeclared ingredients.
2. Do not extrapolate between medicines.
   Do not assume that lactation data, pharmacokinetics, toxicity, or a breastfeeding recommendation for one A08AX medicine applies to another anti-obesity medicine. Separate monographs are required for each drug.
3. Prioritize breastfeeding and maternal nutritional recovery.
   In the early postpartum period, particularly during exclusive breastfeeding, avoid rapid weight-loss strategies, severe caloric restriction, dehydration, fasting, or unregulated “fat-burner” supplements. Use gradual, nutritionally adequate weight management as the default approach unless a compelling maternal medical indication requires pharmacotherapy.
4. Assess maternal nutritional status.
   Review dietary energy intake, protein intake, hydration, micronutrient intake, vomiting, diarrhoea, rate of weight loss, fatigue, sleep quality, mood, and the adequacy of postpartum recovery. Maternal adverse effects can compromise breastfeeding even when direct drug transfer into milk is low.
5. Consider infant-specific vulnerability.
   Use heightened caution for newborn, premature, low-birth-weight, growth-restricted, exclusively breastfed, or medically fragile infants. In these circumstances, a medicine with absent or very limited milk-transfer evidence is generally less acceptable unless maternal benefit is compelling.
6. Do not rely on dose timing without evidence.
   Feeding immediately before a maternal dose, skipping one feed, or briefly expressing and discarding milk may not lower infant exposure meaningfully, particularly for long-acting medicines or agents with active metabolites. Use timing strategies only when supported by known drug-specific milk pharmacokinetics.
7. Use specialist resources and coordinated care.
   Obtain individualized advice from the prescriber, paediatric clinician, clinical pharmacologist, toxicologist, and a specialist medicines-in-lactation service. LactMed is one evidence source that collates milk levels, infant levels, reported infant effects, possible lactation effects, and alternative therapies.datadiscovery.nlm.nih+1
8. Monitor both mother and infant if treatment proceeds.
   Maternal monitoring should include clinical response, adverse effects, blood pressure or glycaemic parameters where relevant, hydration, nutritional status, weight-loss rate, and mental health. Infant monitoring should include feeding quality, sleep, behaviour, hydration, stool pattern, growth trajectory, and any symptom plausibly linked to the medicine’s known pharmacology.