Perazine: Low-Potency Phenothiazine Antipsychotic for Schizophrenia
Perazine is a first-generation (typical) antipsychotic belonging to the phenothiazine chemical class. It has been used in German-speaking countries and parts of Europe for several decades for the treatment of schizophrenia and psychomotor agitation. Compared to high-potency phenothiazines and butyrophenones like haloperidol, perazine is characterised by lower antipsychotic potency and a somewhat different side effect profile with relatively less extrapyramidal side effects.
Perazine occupies a niche in psychiatric practice as a mid-potency typical antipsychotic with sedating properties that may be useful in agitated patients. Its use has declined in many European countries with the availability of second-generation (atypical) antipsychotics, though it remains available in Germany and some other markets.
Mechanism of Action
Like all first-generation antipsychotics, perazine exerts its therapeutic effects primarily by blocking dopamine D2 receptors in the mesolimbic pathway of the brain, which reduces positive psychotic symptoms such as hallucinations and delusions. As a low-potency phenothiazine, perazine also has significant antagonism at muscarinic acetylcholine receptors (anticholinergic effects), histamine H1 receptors (sedation, weight gain), and alpha-1 adrenergic receptors (orthostatic hypotension). The broader receptor binding profile compared to high-potency agents explains the lower incidence of extrapyramidal side effects but higher rates of sedation and anticholinergic effects.
Indications
Perazine is approved for the treatment of schizophrenia and related psychotic disorders. In acute settings, it is used for psychomotor agitation, aggressive behaviour, and acute psychotic episodes. Sedative properties make it useful in managing acute agitation when rapid tranquillisation is needed. It is not indicated for dementia-related psychosis or as a first-line treatment for other psychiatric conditions due to the availability of better-tolerated alternatives.
Dosage and Administration
Oral dosing for schizophrenia typically ranges from 75 to 600 mg daily in divided doses, with the sedating dose often given in the evening. Doses above 600 mg daily are not recommended. For acute agitation, intramuscular administration may be used in hospital settings. The dose should be titrated individually based on response and tolerability, starting at lower doses in elderly and treatment-naive patients. Perazine is available in Germany as tablets and intramuscular injection. Regular reassessment of the therapeutic need and dose is required during long-term treatment.
Side Effects
Sedation is pronounced, particularly at the beginning of treatment. Anticholinergic effects include dry mouth, constipation, urinary retention, blurred vision, and cognitive impairment; these are more pronounced with perazine than with high-potency antipsychotics. Orthostatic hypotension with dizziness and fall risk is a concern, especially in the elderly. Extrapyramidal side effects (EPS) including akathisia, parkinsonism, and acute dystonia occur at lower rates than with haloperidol. Metabolic side effects including weight gain, glucose intolerance, and dyslipidaemia are less pronounced than with some atypical antipsychotics but still relevant. Tardive dyskinesia can develop with long-term use. QTc prolongation has been reported, requiring ECG monitoring in at-risk patients.
Interactions
Concurrent use with other CNS depressants (benzodiazepines, opioids, alcohol) significantly increases sedation and respiratory depression risk. Anticholinergic drugs combined with perazine can cause severe anticholinergic toxidrome. QTc-prolonging drugs (antiarrhythmics, some antibiotics, methadone) should be avoided or used with ECG monitoring. Antihypertensives combined with perazine increase hypotension risk. Levodopa and dopamine agonists for Parkinson's disease may have reduced efficacy when combined with perazine due to D2 antagonism. Enzyme inducers such as carbamazepine may reduce perazine plasma levels.
Special Notes
Perazine is a prescription-only medicine used under psychiatric supervision. It should not be used in patients with known QTc prolongation, hypokalaemia, or concurrent treatment with QTc-prolonging drugs without careful cardiac monitoring. The drug should be used with caution in patients with epilepsy as it lowers seizure threshold. Abrupt discontinuation after long-term treatment should be avoided due to withdrawal symptoms including rebound agitation, nausea, and insomnia. Neuroleptic malignant syndrome (NMS) is a rare but life-threatening complication of antipsychotic treatment characterised by fever, rigidity, autonomic instability, and confusion.
Related Topics
Frequently Asked Questions
How does perazine differ from haloperidol?
Haloperidol is a high-potency antipsychotic with minimal anticholinergic and sedative effects but a high risk of extrapyramidal side effects. Perazine is a lower-potency agent with more sedation and anticholinergic effects but fewer extrapyramidal reactions at equivalent antipsychotic doses. Haloperidol is more potent per milligram and is preferred when rapid control of severe agitation is needed without sedation.
What is tardive dyskinesia and how is it associated with perazine?
Tardive dyskinesia (TD) is a movement disorder characterised by involuntary, repetitive movements, typically of the face, lips, and tongue, caused by long-term dopamine receptor blockade. All first-generation antipsychotics including perazine carry a risk of TD with prolonged treatment. Risk increases with higher doses, longer duration, and older age. TD can persist or be permanent even after the drug is stopped.
Can perazine be used in elderly patients?
Perazine should be used with particular caution in elderly patients due to the pronounced sedation, orthostatic hypotension leading to falls, anticholinergic effects causing delirium and urinary retention, and increased sensitivity to extrapyramidal effects. All antipsychotics, including perazine, carry an increased risk of stroke and death in elderly patients with dementia-related psychosis and should generally be avoided in this population.
Sources
- DGPPN S3-Leitlinie Schizophrenie 2022
- Stahl SM: Essential Psychopharmacology 4th ed.
- Fachinformation Perazin-neuraxpharm, aktueller Stand