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Thiethylperazine (ATC A04AB03) is a phenothiazine‑derived antiemetic used for the prevention and treatment of nausea and vomiting; lactation data are sparse, so cautious, individualized use is recommended in breastfeeding women.medpedia.framar+3

ATC class A04AB03 overview

A04AB03 is the ATC code for thiethylperazine, classified among antiemetics and antinausea drugs that are structurally related to phenothiazines.drugbank+2
The drug is indicated for symptomatic control of nausea and vomiting associated with anesthesia, radiotherapy, chemotherapy, postoperative states and various toxins.pubchem.ncbi.nlm.nih+1

Pharmacological profile

Thiethylperazine is a phenothiazine derivative that acts predominantly as a dopamine receptor antagonist in central emetic pathways, especially in the chemoreceptor trigger zone.medpedia.framar+2
It also exhibits antagonistic activity at histamine H1, muscarinic, adrenergic and certain serotonin receptors, which contributes both to its antiemetic efficacy and to sedative and anticholinergic adverse effects.wikipedia+1

Clinical uses and dosing

Clinically, thiethylperazine is used for short‑term relief or prevention of nausea and vomiting rather than for chronic therapy.mayoclinic+1
Usual adult doses are 10 mg orally, intramuscularly or rectally one to three times daily, titrated to response and kept at the lowest effective dose and shortest duration.drugs.ncats+1

Adverse effects and toxicology

Common adverse effects include drowsiness, lightheadedness, fainting, blurred vision, dry mouth and constipation, reflecting central depressant and anticholinergic actions.alzdiscovery+1
Like other phenothiazines, thiethylperazine may cause extrapyramidal symptoms, hypotension (especially after intramuscular use), lens opacities and cardiac effects, and overdose can lead to profound CNS depression and circulatory collapse.nursing.unboundmedicine+1

Contraindications and precautions

Use is contraindicated in patients with known hypersensitivity to thiethylperazine or other phenothiazine derivatives, or to any excipients in specific formulations.rxlist+1
Caution is required in elderly patients, children, and those with cardiovascular disease, hepatic impairment, seizure disorders or concomitant CNS depressant therapy, because of additive sedative and hypotensive effects.alzdiscovery+1

Drug interactions of toxicological relevance

Thiethylperazine potentiates the effects of other central nervous system depressants such as opioids, sedative hypnotics, alcohol and anesthetics, increasing the risk of excessive sedation and respiratory depression.drugs.ncats+1
Its anticholinergic and alpha‑adrenergic blocking properties can interact with other drugs sharing these mechanisms, leading to enhanced anticholinergic burden, orthostatic hypotension or conduction disturbances.wikipedia+1

Effects on prolactin and endocrine function

Unlike some phenothiazines, thiethylperazine appears less likely to raise prolactin significantly, as it does not strongly block dopamine within the tuberoinfundibular pathway.drugbank
Nevertheless, a potential for mild prolactin elevation remains, and clinicians should be aware of possible galactorrhea or menstrual disturbances with prolonged use.drugbank+1

Lactation: transfer into milk and infant exposure

Almost all orally administered medicines pass to some extent into breast milk, though usually in low concentrations; thiethylperazine is expected to follow this general pattern.ncbi.nlm.nih+1
Specific quantitative data on thiethylperazine levels in human milk and infant serum are limited, so infant exposure is presumed low but not well defined, necessitating case‑by‑case risk assessment.ncbi.nlm.nih+1

Lactation: reported effects in breastfed infants

The Drugs and Lactation Database notes a lack of well‑documented adverse effects in breastfed infants exposed to thiethylperazine, but emphasizes that experience is limited and systematic studies are absent.ncbi.nlm.nih
Potential infant risks extrapolated from its pharmacology include sedation, poor feeding, hypotonia and, with very high exposure, extrapyramidal symptoms or respiratory depression, especially in premature or medically fragile infants.mayoclinic+1

Lactation: effects on milk production

Phenothiazines acting as dopamine antagonists can theoretically increase prolactin and thereby stimulate lactation, or in some cases destabilize established breastfeeding depending on dose and duration.mayoclinic+1
Given thiethylperazine’s relatively modest impact on tuberoinfundibular dopamine, major alterations of milk production are unlikely at short‑term, low‑dose antiemetic use, but long‑term therapy should be avoided in breastfeeding women.ncbi.nlm.nih+1

Toxicological‑lactological risk stratification

From a toxicological‑lactological perspective, thiethylperazine may be considered a second‑line antiemetic in lactation, reserved for situations where safer alternatives (such as certain 5‑HT3 antagonists or other agents with better lactation data) are unsuitable or ineffective.mayoclinic+1
Short courses at the lowest effective dose in healthy term infants are likely to carry a low to moderate risk, whereas use should be avoided or undertaken only with specialist input in preterm infants, neonates with comorbidities or when combined with other sedating drugs.mayoclinic+1

Practical recommendations for breastfeeding patients

When thiethylperazine is considered in a breastfeeding woman, prescribers should evaluate indication strength, expected duration, maternal comorbidities and concurrent medications, and discuss benefits and uncertainties with the family.ncbi.nlm.nih+1
If treatment is initiated, clinicians should monitor the breastfed infant for changes in feeding patterns, sleep, muscle tone, breathing, and overall responsiveness, and discontinue or modify therapy if concerning symptoms arise.mayoclinic+1