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A08AA03 — Amfepramone (Diethylpropion)

ATC class and general pharmacology

ATC code A08AA03 designates amfepramone, also known as diethylpropion. It belongs to the pharmacotherapeutic group of centrally acting anti-obesity products and is an indirectly acting sympathomimetic anorectic.europa

Amfepramone is used as a short-term adjunct to dietary energy restriction in the management of obesity. It is chemically and pharmacologically related to amphetamine-like stimulants and produces appetite suppression through central nervous system activity. Its therapeutic use is generally limited because tolerance may develop and because sympathomimetic and dependence-related risks increase with prolonged exposure.pdf.hres+1

The drug is rapidly absorbed after oral administration and undergoes extensive biotransformation, including N-dealkylation and reduction. Several metabolites are pharmacologically active and may contribute materially to both therapeutic and adverse effects. Elimination is principally renal, and urinary pH may influence the concentrations and excretion of parent drug and metabolites.dailymed.nlm.nih

Amfepramone and its active metabolites can cross the blood–brain barrier and placenta. The pharmacological profile includes central stimulation, anorexia, and increased blood pressure, although the intensity of these effects may differ among individuals because of metabolic variability and concurrent medicines.dailymed.nlm.nih

Toxicological profile

The principal toxicological risks are characteristic of sympathomimetic stimulants: insomnia, nervousness, restlessness, agitation, tremor, headache, dry mouth, nausea, constipation, palpitations, tachycardia, and blood-pressure elevation. Neuropsychiatric reactions may include irritability, anxiety, dysphoria, confusion, hallucinations, or psychotic symptoms in susceptible people or at excessive doses.dailymed.nlm.nih+1

Cardiovascular risk is clinically important. Anorectic medicines including diethylpropion have been associated with pulmonary hypertension, a rare but potentially fatal disorder. Product information reports that use for longer than three months was associated in epidemiological data with a markedly increased risk of pulmonary hypertension. The medicine should therefore be avoided in people with pulmonary hypertension, significant cardiovascular disease, uncontrolled hypertension, arrhythmia, or other conditions in which increased sympathetic activity may be hazardous.dailymed.nlm.nih+1

Amfepramone has abuse and dependence potential and is regulated as a Schedule IV controlled substance in the United States. Tolerance can occur, and escalating the dose in response to reduced appetite suppression is inappropriate and increases toxicity. Abrupt withdrawal after high-dose or prolonged use may be associated with fatigue, depressed mood, and other stimulant-withdrawal manifestations.dailymed.nlm.nih+1

Overdose may cause restlessness, tremor, hyperreflexia, hyperventilation, confusion, aggression, hallucinations, panic states, severe hypertension, arrhythmia, convulsions, and coma. Acute toxicity management is supportive and requires medical supervision, with attention to cardiovascular status, temperature, neurological symptoms, and seizure control.drugbank

Lactation pharmacology and infant exposure

Human evidence on amfepramone during lactation is very limited. No reliable published datasets establish milk-to-plasma ratios, absolute milk concentrations, relative infant dose, infant serum concentrations, or systematic neurodevelopmental outcomes after exposure through breast milk. This lack of quantitative evidence prevents a confident estimate of infant dose.

Nevertheless, manufacturer information indicates that diethylpropion and/or its metabolites are excreted in human milk. A Canadian product monograph states that the presence of diethylpropion or its metabolites in milk was not known at the time of that document and recommended against use in nursing women; the difference in wording between product sources reflects limitations and historical variation in the underlying lactation evidence rather than a demonstrated absence of transfer.pdf.hres+1

Potential infant exposure is pharmacologically important because amfepramone is a centrally active, orally bioavailable sympathomimetic and because several active metabolites may contribute to activity. If appreciable transfer occurs, an infant may be vulnerable to irritability, excessive wakefulness, disturbed sleep, tremor, poor feeding, reduced appetite, tachycardia, hypertension, poor weight gain, or—in severe exposure—neurological and cardiorespiratory toxicity. These effects are biologically plausible extrapolations from known stimulant pharmacology; they should not be represented as documented outcomes in breastfed infants.

A further lactation-related concern is possible suppression of maternal appetite and inadequate maternal energy or fluid intake. In the early postpartum period, restrictive dieting combined with an anorectic stimulant may compromise maternal nutritional adequacy, recovery, and, in some cases, maintenance of an adequate milk supply.

Lactological safety assessment and clinical recommendations

Amfepramone should generally be regarded as not recommended during breastfeeding. The recommendation is based on evidence or product information suggesting milk excretion, the presence of active metabolites, amphetamine-like central and cardiovascular toxicity, misuse potential, and the absence of adequate infant-exposure and outcome data.pdf.hres+1

In routine postpartum weight management, treatment should usually be postponed until breastfeeding has ended. First-line management should instead include nutritionally adequate dietary support, gradual weight reduction, physical activity adjusted to postpartum recovery, sleep optimisation, and assessment for medical causes of persistent weight gain. Anti-obesity pharmacotherapy that offers no immediate maternal lifesaving benefit is usually difficult to justify when its lactation safety is uncertain.

If exposure occurs inadvertently, management should be individualized according to maternal dose, formulation, duration of treatment, time since the last dose, infant age, prematurity, breastfeeding intensity, and infant clinical status. A paediatric clinician should assess the infant if exposure has been repeated, substantial, or associated with symptoms.

Infants with possible exposure should be monitored for:

• Poor suck, feeding difficulty, reduced appetite, or reduced milk intake
• Irritability, jitteriness, tremor, agitation, or unusual crying
• Insomnia, unusually prolonged wakefulness, or disrupted sleep
• Tachycardia, sweating, pallor, breathing changes, or signs of hypertension
• Inadequate weight gain, dehydration, or reduced urine output

Urgent paediatric review is appropriate for marked agitation, tremor, persistent feeding refusal, rapid heartbeat, breathing difficulty, seizure-like activity, lethargy, or poor weight gain. No evidence-based interval can be specified for timing feeds around a dose or for resuming breastfeeding after treatment, because human milk pharmacokinetic data are inadequate and active metabolite exposure is uncertain.