LACTOLOGY FOUNDATION

A07AX02 corresponds to acetarsol (acetarsone, stovarsol), a pentavalent organoarsenical antiinfective classified among “other intestinal antiinfectives”, historically used for intestinal amoebiasis and other protozoal infections. From a toxicological‑lactological perspective, its arsenic‑based systemic toxicity, urinary arsenic levels near the toxic range, and lack of modern lactation data make acetarsol unsuitable for routine use in breastfeeding; safer alternatives should be preferred whenever possible.atcddd.fhi+4

ATC classification and substance identity

Acetarsol is assigned ATC code A07AX02 within group A07 “Antidiarrheals, intestinal anti‑inflammatory/anti‑infective agents” and subgroup A07A “Intestinal antiinfectives”.atcddd.fhi+1
A07AX “Other intestinal antiinfectives” is reserved for agents that cannot be classified as intestinal antibiotics (A07AA), sulfonamides (A07AB), or imidazole derivatives (A07AC).bionity+1

Chemically, acetarsol (N‑acetyl‑4‑hydroxy‑m‑arsanilic acid) is a pentavalent arsenical compound with antiprotozoal and anthelmintic properties.drugbank+1
It was first discovered in 1921 at the Pasteur Institute, marketed under names such as Stovarsol, and later withdrawn from many markets due to safety concerns.wikipedia+1

Pharmacodynamic properties

Acetarsol exerts antiprotozoal and antihelmintic activity by interfering with parasite metabolism through its arsenic moiety, binding to essential sulfhydryl groups in enzymes and disrupting cellular respiration and replication.pmc.ncbi.nlm.nih+2
These actions lead to inhibition of growth and death of susceptible protozoa and helminths, including amoebae and certain vaginal or intestinal pathogens.drugbank+1

As an arsenical, its toxicity to parasites is closely related to the same mechanisms that can cause toxicity in human cells, a classic example of “on‑target” pharmacological toxicity.pmc.ncbi.nlm.nih+1
This narrow therapeutic window underpins the need for great caution in dosing and treatment duration.wikipedia+1

Therapeutic indications and clinical use

Historically, acetarsol was used for a wide range of infections: syphilis, amoebiasis, yaws, trypanosomiasis, malaria, and vaginitis due to Trichomonas vaginalis and Candida albicans.drugbank+1
Oral acetarsol tablets were used for intestinal amoebiasis, while suppositories were investigated for proctitis and refractory proctitis in inflammatory bowel disease cohorts.pubmed.ncbi.nlm.nih+1

The drug has been withdrawn or cancelled from many markets since the late 1990s due to safety and regulatory concerns, and its current use is mainly limited to research contexts or highly selected refractory cases.pubmed.ncbi.nlm.nih+2
Modern practice generally favours safer, non‑arsenical agents (e.g., metronidazole, modern antiparasitics) for the same indications.pubmed.ncbi.nlm.nih+1

Dosage, DDD and administration

The ATC/DDD index lists acetarsol under A07AX02 but does not assign a commonly used Defined Daily Dose, reflecting limited current utilisation.atcddd.fhi+1
Historically, oral dosing regimens varied depending on indication and product, often involving multiple daily doses over several days, with close monitoring for signs of arsenic toxicity.drugbank+1

Rectal suppositories have been studied for refractory proctitis, with one cohort showing clinical response in about two‑thirds of patients and relatively few acute adverse effects.pubmed.ncbi.nlm.nih
However, even local rectal administration can result in arsenic absorption, necessitating cautious risk assessment, especially for repeated or prolonged courses.wikipedia+1

Pharmacokinetics and systemic arsenic exposure

The arsenic in acetarsol is excreted mainly in urine, and measured urinary arsenic levels after administration can approach the toxic range.wikipedia
This indicates substantial systemic absorption and necessitates consideration of cumulative body burden and long‑term toxicity, particularly with repeated courses or high doses.pmc.ncbi.nlm.nih+1

Distribution of arsenic compounds can involve multiple organs (nervous system, skin, liver, kidneys), and chronic exposure is known to cause peripheral neuropathy, skin changes, and organ damage.pmc.ncbi.nlm.nih+1
No detailed breast milk pharmacokinetic data for acetarsol are available, but given systemic absorption and urinary excretion, passage into breast milk is biologically plausible.pmc.ncbi.nlm.nih+1

Toxicological profile in adults

Short‑term use of acetarsol may cause gastrointestinal upset, rash and other hypersensitivity reactions; in the refractory proctitis cohort, macular rash was reported and resolved after drug cessation.pubmed.ncbi.nlm.nih+1
Long‑term or high‑dose use can lead to arsenic toxicity, manifesting as peripheral neuropathy, skin discoloration or keratosis, gastrointestinal complaints, and in severe cases multi‑organ involvement.wikipedia+1

Because toxicity arises from the same arsenic‑mediated mechanisms as therapeutic effects, the margin between effective and toxic doses is relatively narrow.pmc.ncbi.nlm.nih+1
This, together with regulatory decisions and safer alternatives, explains why acetarsol has largely disappeared from routine clinical practice.drugbank+1

Lactational safety and infant risk

General breastfeeding pharmacology indicates that most medicines are excreted into breast milk at less than 10% of the maternal dose, and many can be used safely; however, substances with high inherent toxicity or narrow therapeutic margins demand special caution.pmc.ncbi.nlm.nih+1
Pentavalent arsenicals like acetarsol carry systemic toxicity risks for adults, and potential passage of arsenic into breast milk raises concern for infant exposure even at small fractions of the maternal dose.wikipedia+1

Given the absence of reassuring lactation‑specific pharmacokinetic or clinical outcome data, and the known toxicity of arsenic, acetarsol should generally be considered incompatible or strongly discouraged in breastfeeding women.pmc.ncbi.nlm.nih+1
Theoretical risks include neurodevelopmental impact, organ toxicity, and cumulative arsenic burden in the infant, particularly with repeated or prolonged maternal therapy.pmc.ncbi.nlm.nih+1

Clinical recommendations for breastfeeding women

Modern lactation guidance emphasises using the lowest effective dose for the shortest time and preferring medicines with well‑characterised safety profiles in breastfeeding.pmc.ncbi.nlm.nih+1
For indications historically treated with acetarsol (e.g., amoebiasis, vaginitis, proctitis), safer alternatives such as metronidazole, other modern antiparasitics, or non‑arsenical therapies should be selected whenever available.pubmed.ncbi.nlm.nih+1

If acetarsol A07AX02 is being considered (for example, in refractory proctitis where other options have failed), an individualised and specialist‑level risk–benefit assessment is required, explicitly including the breastfeeding status of the mother.who+1
In most such high‑risk scenarios, temporary interruption of breastfeeding with appropriate lactation support, or complete avoidance of acetarsol, will be preferable to exposing the infant to arsenic.who+1

Clinicians should counsel mothers about the lack of lactation data, potential arsenic toxicity, and the rationale for choosing alternative treatments or altering breastfeeding plans.pmc.ncbi.nlm.nih+1
Infant monitoring for signs of toxicity would be difficult and non‑specific; therefore, prevention of exposure by avoiding acetarsol use in breastfeeding is the safest strategy.pmc.ncbi.nlm.nih+1

Educational summary for practice

A07AX02 acetarsol is a pentavalent arsenical classified as an “other intestinal antiinfective”, historically used for intestinal amoebiasis, vaginitis and refractory proctitis.atcddd.fhi+2
Its systemic arsenic exposure, urinary levels near toxic ranges, and established potential for serious toxicity make it unsuitable for routine use in breastfeeding women.wikipedia+1

In toxicological‑lactological practice, acetarsol should be regarded as a non‑preferred or contraindicated option in lactating mothers, with safer non‑arsenical agents chosen instead.pmc.ncbi.nlm.nih+2
When acetarsol is contemplated for exceptional indications, careful documentation, consideration of alternative therapies, and strong preference for avoiding infant exposure through breastfeeding are essential.who+1