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Pepsin (ATC A09AA03): Toxicological and Lactation Monograph

ATC Class and General Pharmacology

Pepsin is classified as ATC A09AA03 within the World Health Organization Anatomical Therapeutic Chemical classification system:

• A — Alimentary Tract and Metabolism
• A09 — Digestives, including enzymes
• A09AA — Enzyme preparations
• A09AA03 — Pepsin

The A09AA subgroup includes enzyme preparations used in digestive disorders, and A09AA03 is specifically assigned to pepsin.atcddd.fhi

Pepsin is a proteolytic digestive enzyme physiologically present in gastric juice. It is secreted as the inactive precursor pepsinogen by gastric chief cells and becomes active primarily in an acidic gastric environment. Its principal function is to initiate digestion of dietary proteins by hydrolysing peptide bonds and generating smaller peptides that undergo further digestion in the small intestine.

Medicinal pepsin has traditionally been prepared from animal gastric mucosa, including porcine, bovine, or ovine sources. The biological source, enzyme activity, purity, manufacturing processes, formulation, and excipients may differ between products and countries. Pepsin may be supplied as a single-ingredient enzyme product, but it is frequently combined with other digestive enzymes, acidifying agents, amino acids, vitamins, or symptomatic gastrointestinal products. The clinical and lactation assessment must therefore be based on the full formulation rather than the presence of pepsin alone.drugs

The pharmacological effect of oral pepsin is principally local to the gastrointestinal tract. Its enzymatic activity is greatest at acidic pH and decreases markedly as gastric pH rises. Consequently, oral pepsin is sometimes combined with acidifying components intended to support an environment favourable to proteolysis. It is not intended to exert systemic pharmacological effects after absorption.

The clinical role of pepsin-containing preparations is generally supportive. They may be used for dyspeptic symptoms or as adjunctive treatment in selected situations involving perceived impaired protein digestion. However, persistent dyspepsia, early satiety, vomiting, dysphagia, gastrointestinal bleeding, unexplained weight loss, anaemia, or persistent abdominal pain should be medically evaluated rather than treated empirically with digestive enzyme products.

Toxicological Profile

The toxicological profile of orally administered pepsin is usually dominated by local gastrointestinal effects. Pepsin is a proteinaceous enzyme that is expected to be exposed to gastric acid, endogenous proteases, intestinal secretions, and normal digestive degradation. Intact systemic absorption following oral use is therefore expected to be very limited.

At conventional doses, adverse effects are generally mild and may include:

• Epigastric discomfort, dyspepsia, abdominal pain, or abdominal bloating
• Nausea or vomiting
• Diarrhoea, constipation, or altered bowel habit
• Gastric irritation or worsening of reflux-related symptoms
• Local irritation of the oral cavity or oesophagus if powder, tablets, or capsules are chewed, retained in the mouth, or taken without adequate fluid
• Intolerance related to accompanying acids, other enzymes, preservatives, flavourings, or excipients

The most important product-related toxicological concern is the potential for increased mucosal irritation where pepsin is combined with acidifying agents. Pepsin is active in an acidic environment, and acid–pepsin formulations may worsen symptoms in people with active peptic ulcer disease, erosive gastritis, oesophagitis, severe gastro-oesophageal reflux disease, or other conditions involving compromised upper gastrointestinal mucosa. Peptic ulcer disease and gastritis are commonly identified as conditions in which pepsin supplementation should be avoided or used only following medical assessment.synapse.patsnap

Hypersensitivity is an uncommon but clinically relevant concern. Because medicinal pepsin may be derived from animal gastric mucosa, patients with a known allergy to relevant animal-derived proteins, to pepsin itself, or to a formulation component require particular caution. Possible manifestations include rash, urticaria, itching, angioedema, wheezing, or other allergic symptoms.

Toxicological risk differs substantially between regulated medicinal products and food supplements. Non-prescription “digestive enzyme” products may contain variable enzyme concentrations and unassessed combinations of pepsin with betaine hydrochloride, herbal extracts, probiotics, other enzymes, alcohol-containing liquid vehicles, or high-dose nutritional ingredients. These products should not be presumed equivalent to a licensed single-ingredient pepsin medicine.

Lactation Pharmacology and Infant Exposure

There are limited direct studies measuring pepsin concentrations in human milk after maternal oral use. Therefore, the lactation assessment relies primarily on the physicochemical and pharmacological characteristics of the enzyme rather than on robust human milk pharmacokinetic data.

Pepsin is a protein digestive enzyme whose intended activity is confined to the maternal gastrointestinal tract. Intact maternal systemic absorption after oral administration is expected to be negligible because the enzyme is susceptible to denaturation, degradation, and digestion within the gastrointestinal tract. As a result, clinically meaningful concentrations in maternal plasma and subsequent transfer into breast milk are unlikely.

If a small quantity of pepsin or pepsin-derived protein were present in milk, it would be expected to undergo digestion in the infant gastrointestinal tract. This makes systemic pharmacological exposure of the infant biologically implausible. Importantly, human milk itself contains a complex range of bioactive proteins and proteolytic enzymes; however, this physiological observation does not replace product-specific evidence for medicinal pepsin preparations.

There is no pharmacological basis to expect maternal use of pepsin alone to suppress milk production, alter prolactin regulation, meaningfully change milk composition, or impair infant protein metabolism through breast milk exposure. The principal lactation concern is usually the complete product formulation, not pepsin as an isolated enzyme.

In particular, individual assessment is required where a pepsin product also contains:

• Hydrochloric acid, betaine hydrochloride, or another acidifying compound
• Other digestive enzymes with separate safety considerations
• Herbal ingredients or poorly characterized botanical extracts
• Alcohol-containing syrup vehicles
• High-dose vitamins, minerals, amino acids, or other pharmacologically active constituents

Maternal nutritional status is also relevant. Women with persistent dyspepsia, vomiting, poor intake, gastrointestinal disease, malabsorption, or clinically significant weight loss may require investigation and nutritional support. Optimizing maternal health can support continued breastfeeding more effectively than repeated self-treatment with enzyme combinations.

Lactological Safety Assessment and Clinical Recommendations

A conventional, single-ingredient oral pepsin preparation is expected to pose low risk during breastfeeding when used at standard doses and for an appropriate clinical indication. This conclusion is based on low expected intact systemic absorption, low plausibility of meaningful transfer into milk, and likely gastrointestinal digestion of any trace enzyme material by the breastfed infant.

Nevertheless, direct lactation data for pepsin are sparse. The assessment should therefore be expressed as a pharmacologically reasoned, low-risk conclusion rather than a definitive statement supported by extensive milk-level and infant-outcome studies.

Breastfeeding interruption, temporary cessation, or routine disposal of milk is not generally expected to be required because of maternal use of pepsin alone. Where treatment is necessary, preserving maternal gastrointestinal health and adequate nutritional intake is preferable to unnecessary discontinuation of breastfeeding or clinically indicated therapy.

Clinical recommendations

• Prefer a regulated, clearly labelled, single-ingredient pepsin product when pepsin is considered necessary during breastfeeding.
• Confirm the complete formulation before recommending use. Pepsin-containing combinations require separate lactation assessment of every active ingredient and relevant excipient.
• Avoid non-standardized digestive-enzyme supplements with unclear enzyme activity, uncertain animal source, unverified botanical additives, or alcohol-containing liquid formulations.
• Use the lowest effective dose for the shortest appropriate duration unless continued treatment has a specific medical rationale.
• Avoid empiric self-treatment of persistent, recurrent, or severe dyspeptic symptoms. Medical assessment is required when alarm features are present, including weight loss, gastrointestinal bleeding, dysphagia, persistent vomiting, anaemia, severe pain, or progressive symptoms.
• Avoid or obtain specialist advice before use in mothers with active peptic ulcer disease, erosive gastritis, severe reflux disease, oesophagitis, or suspected upper gastrointestinal mucosal injury, particularly if the product contains an acidifying agent.synapse.patsnap
• Avoid use in patients with known hypersensitivity to pepsin, relevant animal-derived proteins, or any component of the formulation.
• Consider non-pharmacological dyspepsia management first where clinically suitable, including dietary measures and avoidance of individual symptom triggers. Evidence-based treatments for heartburn and dyspepsia during breastfeeding include alginates and selected antacids; specialist guidance also supports several acid-suppressing treatments when needed.sps

Infant monitoring

No routine infant monitoring is usually necessary when the mother uses a conventional single-ingredient oral pepsin preparation and the infant is healthy and born at term. As a prudent precaution, caregivers may observe the infant for unexpected gastrointestinal symptoms or hypersensitivity features.

Clinical review is appropriate if an infant develops persistent vomiting, diarrhoea, rash, wheeze, marked feeding difficulty, unusual irritability, or inadequate weight gain. Such findings would be unlikely to arise from maternal pepsin exposure through milk and should prompt evaluation for alternative causes, including infection, feeding problems, food-protein allergy, or an independent infant gastrointestinal condition.

More individualized review is reasonable for mothers of premature infants, infants with serious gastrointestinal disease, infants with complex medical conditions, or infants with known severe food or protein allergies. This precaution principally reflects the infant’s clinical vulnerability and uncertainty regarding complex product formulations rather than an anticipated risk from pepsin itself.

Overall conclusion

Pepsin (A09AA03) is an orally administered proteolytic digestive enzyme classified among digestive enzyme preparations. It acts predominantly in the gastrointestinal tract, and intact systemic absorption after maternal oral use is expected to be negligible. Therefore, clinically significant passage into breast milk and systemic exposure of the breastfed infant are unlikely.atcddd.fhi

For a standard single-ingredient pepsin preparation, breastfeeding can generally continue. The most important safety limitation is the frequent use of pepsin in combination products—especially formulations containing acidifying agents, herbal extracts, or poorly standardized supplement ingredients. A product-specific assessment remains essential in these circumstances.