spec sheet7 rows
Alimemazine is a sedating phenothiazine antihistamine used at low dose for anxiety, itch and sleep, and at higher dose as a weak antipsychotic.
- Reliable, heavy sedation from strong H1 blockade
- Low doses take the edge off anxiety and itch
- A defensible, long established choice in paediatric sedation
- Settles stubborn itch that nothing else will touch
- Weak antipsychotic activity available at higher doses
- Alimemazine is a phenothiazine, not a simple antihistamine; its structure is promethazine's, and it carries the phenothiazine liability profile including extrapyramidal effects and, rarely, neuroleptic malignant syndrome.
- No published receptor binding constant for alimemazine could be located in ChEMBL or the indexed literature; ChEMBL curates only the qualitative mechanism 'histamine H1 receptor antagonist' (CHEMBL3989885), so any numeric affinity claim for this compound should be treated as unsourced.
- The best-quality clinical evidence is small and paediatric: a randomised trial for retching after Nissen fundoplication [1] and a controlled comparison as oral premedication in children [2].
- Trimeprazine pharmacokinetics in children show wide interindividual variability, which is directly relevant to the overdose reports [3].
- Alimemazine is not marketed in the United States; it is used mainly in the UK, France, Norway and Russia, and Norwegian prescribing data show it is heavily used as a paediatric hypnotic in families where the parent is also prescribed a hypnotic [8].
- It has been documented as an agent of poisoning in Munchausen syndrome by proxy, and it can paradoxically induce restless legs syndrome (PMID 27567044, PMID 28647108).
Mechanism
It blocks H1 receptors strongly along with , and alpha1 sites. The H1 and muscarinic blockade give the sedation and the drying, and the D2 blockade is what makes higher doses behave like a low potency neuroleptic.
receptor fingerprint
H1 receptor (HRH1)Antagonist / inverse agonist
receptors (M1-M5)Antagonist (phenothiazine class effect)
receptorAntagonist (phenothiazine class effect)
receptorAntagonist (phenothiazine class effect; alimemazine is a weak neuroleptic and was historically used at high dose in agitation)
Alpha-1 adrenoceptorAntagonist (phenothiazine class effect)
Safetyrisks and cautions, not medical advice
a phenothiazine, so it carries the class risks of extrapyramidal reactions and QT prolongation on top of heavy sedation and a substantial anticholinergic load
Subjective profileweighing the evidence above
Sedation from a phenothiazine is sedation bought at a price most people do not need to pay. The H1 blockade will reliably make someone drowsy, but the muscarinic, D2 and alpha1 blockade riding along with it brings dry mouth, orthostatic drops and, at antipsychotic strength, genuine extrapyramidal risk; in older adults the anticholinergic load alone tracks with falls and confusion. It keeps a defensible place in paediatric sedation and in itch that will not settle, and outside those the newer antihistamines do the same job with less collateral.
Where to buy
Suppliers
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Alimemazine
Research
- 1986first cited[Biotransformation of alimemazine].
- 2005controlled trialEffectiveness of alimemazine in controlling retching after Nissen fundoplication.
- 2020most recent[Alimemazine in treatment of agitation in schizophrenia].
- 1.Effectiveness of alimemazine in controlling retching after Nissen fundoplication.
- 2.Oral premedication in children.
- 3.Pharmacokinetics of trimeprazine in children.
- 4.[Biotransformation of alimemazine].
- 5.[Alimemazine in treatment of agitation in schizophrenia].
- 6.Alimemazine poisoning as evidence of Munchausen syndrome by proxy: A pediatric case report.
- 7.[Alimemazine-induced restless legs syndrome: About two cases].
- 8.Association between prescribing hypnotics for parents and children in Norway.
8 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
Notes and cautions
- Alimemazine is contraindicated in children under 2 years, where sedating phenothiazine antihistamines have caused fatal respiratory depression and apnoea; this is the same hazard that carries a boxed warning for promethazine in the United States.
- Its sedation is deep and long-lasting, additive with alcohol, opioids, benzodiazepines and gabapentinoids, and it produces next-day impairment that makes driving unsafe.
- As a phenothiazine it can prolong the QT interval, lower the seizure threshold, cause extrapyramidal reactions and, rarely, neuroleptic malignant syndrome, and its anticholinergic load makes it a poor choice in older adults, in glaucoma and in prostatic hypertrophy.
- It is not a nootropic and there is no cognitive-enhancement literature for it; the anticholinergic burden argues in the opposite direction.