1. Clinical Overview
Flupenthixol is a high-potency, first-generation (typical) thioxanthene antipsychotic. It acts as a potent dopamine D1 and D2 receptor antagonist, with additional serotonin 5-HT2A antagonism. The 0.5mg strength is primarily indicated for the maintenance treatment of chronic schizophrenia and other psychoses, and for depressive symptoms associated with schizophrenia and depression with anxiety. It is known for its long-acting properties and activating profile, making it suitable for withdrawn, apathetic, or anergic patients.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: Therapeutic effects on psychosis may take 2-4 weeks to become fully apparent, though initial calming effects may be seen within hours to days. Peak plasma concentration occurs approximately 4 hours after oral administration. | Long-acting due to high lipophilicity and extensive tissue binding. The elimination half-life is approximately 35 hours, allowing for once-daily dosing. | Approximately 40-55% after oral administration due to significant first-pass metabolism. |
2. Mechanism of Action
Flupenthixol exerts its antipsychotic effect primarily by blocking postsynaptic dopamine D1 and D2 receptors in the mesolimbic and mesocortical pathways of the brain. Its blockade of D2 receptors in the nigrostriatal pathway is responsible for extrapyramidal side effects. Additional blockade of serotonin 5-HT2A receptors may contribute to a lower incidence of EPS compared to pure D2 antagonists and provide some mood-elevating effects. Its alpha-1 adrenergic blockade is minimal, leading to less sedation and hypotension.
3. Indications & Uses
- Maintenance treatment of chronic schizophrenia
- Management of other psychotic disorders (e.g., schizoaffective disorder, delusional disorder)
4. Dosage & Administration
Adult Dosage: Schizophrenia/Psychosis: Initial dose: 1-3 mg daily in divided doses. Maintenance: 3-6 mg daily in divided doses or as a single morning dose. The 0.5mg tablet allows for fine titration. Max daily dose rarely exceeds 12-18 mg. For depressive symptoms: 0.5-1 mg once daily in the morning.
Administration: Administer orally with or without food. To minimize insomnia, take the total daily dose in the morning. The tablet can be broken for dose titration. Avoid abrupt discontinuation.
5. Side Effects
Common side effects may include:
- Extrapyramidal Symptoms (EPS): Akathisia (restlessness), dystonia, parkinsonism (tremor, rigidity, bradykinesia)
- Insomnia (if taken late in the day)
- Dry mouth
- Constipation
- Blurred vision
- Weight gain (mild)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Levodopa, Dopamine Agonists (e.g., Pramipexole) | Mutual antagonism of effects; flupenthixol reduces efficacy of dopaminergic drugs. | Major |
| Other CNS Depressants (Alcohol, Benzodiazepines, Opioids) | Additive CNS and respiratory depression, increased sedation. | Major |
| Anticholinergic drugs (e.g., Trihexyphenidyl, Benztropine) | May reduce EPS but can worsen constipation, blurred vision, and cognitive effects. | Moderate |
| Drugs prolonging QTc (e.g., Erythromycin, Amiodarone, TCAs, Citalopram) | Additive risk of QTc prolongation, torsades de pointes. | Major |
| Enzyme Inducers (e.g., Carbamazepine, Phenytoin, Rifampicin) | May decrease flupenthixol plasma levels, reducing efficacy. | Moderate |
| Enzyme Inhibitors (e.g., Fluoxetine, Paroxetine, Ketoconazole) | May increase flupenthixol plasma levels, increasing toxicity risk. | Moderate |
| Antihypertensives | Potentiation of hypotensive effects. | Moderate |
7. Patient Counselling
- DO take the medication exactly as prescribed, usually in the morning.
- DO keep all follow-up appointments with your doctor for monitoring.
- DO inform all your doctors and dentists you are taking this medicine.
- DO report any unusual movements, restlessness, fever, or fast heartbeat immediately.
- DONT stop taking the medicine suddenly without consulting your doctor.
- DONT consume alcohol while on this medication.
- DONT drive or operate heavy machinery until you know how the medicine affects you.
- DONT take over-the-counter medicines (especially for cold, allergy, sleep) without checking with your doctor or pharmacist.
8. Toxicology & Storage
Overdose: Symptoms are primarily extensions of pharmacological effects: Severe extrapyramidal reactions (oculogyric crisis, trismus), profound CNS depression (coma), hypotension, tachycardia, cardiac arrhythmias (QTc prolongation), seizures, agitation, confusion, hyperthermia or hypothermia. Anticholinergic symptoms (dry mouth, ileus) may also occur.
Storage: Store below 30°C, in a cool, dry place, protected from light and moisture. Keep the container tightly closed. Keep out of reach and sight of children.