Levomepromazine: Antipsychotic and Palliative Care Medication
Levomepromazine (also known as methotrimeprazine in some countries) is a low-potency phenothiazine antipsychotic with a uniquely broad pharmacological profile that combines antipsychotic, antiemetic, sedative, anxiolytic, and analgesic-potentiating properties within a single molecule. It was introduced in the 1950s and is classified as a conventional (typical) antipsychotic of the aliphatic phenothiazine subclass, closely related to chlorpromazine but with a more sedating character.
While levomepromazine is used in psychiatry for the treatment of psychotic disorders, its most significant contemporary role is in palliative medicine. The combination of antiemetic, anxiolytic, and sedative effects makes it particularly valuable in managing symptoms of terminally ill patients, including nausea, agitation, and distressing dyspnoea. It is available as an oral preparation and as a solution for subcutaneous injection, the latter being especially important in palliative care where the oral route may no longer be feasible.
Mechanism of Action
Levomepromazine exerts its effects through broad antagonism of multiple receptor systems. Dopamine D2 receptor blockade in the mesolimbic and mesocortical pathways underpins its antipsychotic effect. Antagonism at dopamine receptors in the chemoreceptor trigger zone (CTZ) in the area postrema produces the antiemetic effect. Histamine H1 receptor antagonism causes sedation and contributes to antiemetic activity. Alpha-1 adrenergic receptor blockade leads to vasodilation and orthostatic hypotension, which is the most clinically problematic side effect. Muscarinic acetylcholine receptor antagonism produces anticholinergic effects. Serotonin receptor antagonism contributes to anxiolytic and antidepressant components. This polyreceptor profile distinguishes levomepromazine from higher-potency phenothiazines such as haloperidol, which have far more selective D2 activity with correspondingly different side effect profiles.
Indications
In psychiatry, levomepromazine is used for acute and chronic schizophrenia, treatment-resistant psychoses, and as adjunctive sedation in acute agitation. In palliative medicine, levomepromazine is used for nausea and vomiting refractory to standard antiemetics, terminal agitation and delirium, anxiety and restlessness in dying patients, and as part of palliative sedation protocols. It is also used as a premedication in anaesthesia due to its antiemetic and sedating properties. In pain management, levomepromazine has been used as an opioid adjuvant in severe cancer pain, particularly where its sedating and anxiolytic properties are additionally beneficial.
Dosage and Administration
Psychiatric indications: 25 to 300 mg daily in divided doses orally; doses are typically lower in elderly patients (12.5 to 50 mg daily). Antiemetic use in palliative care: 6.25 to 25 mg subcutaneously as a single daily dose or continuous infusion via syringe driver. For terminal agitation: 12.5 to 200 mg per 24 hours subcutaneously, titrated to symptom control. In palliative care, levomepromazine is often combined in syringe drivers with opioids (morphine, diamorphine) and midazolam; compatibility of these combinations should be verified with pharmacist guidance. Oral tablets should be taken with food. Due to pronounced sedation, the majority of the daily dose is often given at night.
Side Effects
Orthostatic hypotension is the most common and clinically significant adverse effect of levomepromazine. It results from alpha-1 adrenoceptor blockade and can cause dizziness, lightheadedness, and falls, particularly in elderly patients and after rising from a supine or seated position. Patients should be advised to change positions slowly and should be at rest for at least 30 minutes after injection. Sedation is prominent and is often dose-limiting in ambulatory psychiatric patients but therapeutically useful in palliative settings. Anticholinergic effects include dry mouth, urinary retention, constipation, and blurred vision. Extrapyramidal effects (parkinsonism, akathisia, acute dystonia, tardive dyskinesia) occur less frequently than with high-potency antipsychotics due to the lower D2 receptor affinity, but remain a possibility with prolonged use. QT prolongation with the risk of arrhythmias is a class effect of phenothiazines. Weight gain and metabolic effects are associated with long-term use in psychiatric patients.
Interactions
CNS depressants including opioids, benzodiazepines, barbiturates, alcohol, and general anaesthetics have additive sedative effects; this combination requires dose adjustment and careful monitoring, though in palliative care the combination is often intentional and medically supervised. Antihypertensive agents combined with levomepromazine may cause excessive blood pressure reduction through additive alpha-1 blockade. QT-prolonging drugs (antiarrhythmics, antidepressants, antifungals, macrolide antibiotics) increase the risk of potentially fatal arrhythmias. Anticholinergic drugs (tricyclic antidepressants, antiparkinson drugs, antihistamines) combined with levomepromazine may cause severe anticholinergic toxicity. Levodopa and dopamine agonists may be rendered less effective by dopamine receptor blockade. Lithium combined with phenothiazines has been associated with increased neurotoxicity in some case reports; close monitoring is advised.
Special Notes
Levomepromazine is a prescription-only medicine. Due to the high risk of orthostatic hypotension, patients receiving oral or subcutaneous levomepromazine should be advised to remain recumbent for a period after dosing, particularly when the drug is introduced or the dose is increased. Blood pressure monitoring is recommended at treatment initiation. Levomepromazine should be used with caution in patients with hepatic impairment, epilepsy (lowers seizure threshold), prostatic hypertrophy, and glaucoma. It is generally not recommended in dementia patients with behavioral disturbance due to increased mortality risk associated with antipsychotics in this population. Use in pregnancy should be restricted to clear clinical necessity; the drug crosses the placenta. The injectable formulation for subcutaneous use has been used extensively in hospice and palliative care settings and its use in symptom management at end of life is well-supported by palliative care guidelines.
Related Active Ingredients
Frequently Asked Questions
Why is levomepromazine used in palliative care?
Levomepromazine offers a unique combination of effects that are highly relevant in end-of-life care: it suppresses nausea via dopamine and histamine receptor blockade in the brain, reduces anxiety through histamine and serotonin receptor antagonism, and provides sedation through multiple mechanisms. The availability of a subcutaneous injectable form allows administration when patients can no longer swallow. No other single drug combines antiemetic, anxiolytic, and sedative properties in a single subcutaneous injection as effectively as levomepromazine.
What is the main risk with levomepromazine?
The greatest safety concern in outpatient use is orthostatic hypotension, which can cause falls and injuries, particularly in elderly patients. This results from blockade of alpha-1 adrenergic receptors that normally maintain vascular tone during position changes. Patients should be counseled to change position slowly and to sit on the edge of the bed before standing. Monitoring of blood pressure at treatment initiation is advisable.
How does levomepromazine differ from haloperidol in palliative care?
Haloperidol is a high-potency antipsychotic with strong and selective D2 receptor blockade, making it effective for delirium and antiemesis with less sedation and less hypotension. Levomepromazine is lower-potency with broader receptor blockade, causing more sedation, more hypotension, but also additional anxiolytic effect. In patients with delirium without prominent anxiety, haloperidol is often preferred. In patients with combined nausea, agitation, and anxiety, levomepromazine may be the more practical choice as it addresses all three simultaneously.
Sources
- Palliative Care Formulary (PCF7): Levomepromazine monograph 2023
- EAPC Atlas of Palliative Care in Europe 2022
- Twycross R et al: Introducing Palliative Care, 6th ed. Radcliffe Publishing 2021