1. Clinical Overview
Amisulpride is an atypical antipsychotic belonging to the benzamide class. It is a selective dopamine D2 and D3 receptor antagonist with high affinity and low nanomolar potency. At low doses (50-300 mg/day), it preferentially blocks presynaptic dopamine autoreceptors, increasing dopaminergic neurotransmission, making it effective for negative symptoms and dysthymia. At higher doses (>400 mg/day), it blocks postsynaptic receptors, treating positive psychotic symptoms. It has minimal affinity for serotonin, histamine, adrenergic, and cholinergic receptors, contributing to a favorable side effect profile regarding sedation, weight gain, and anticholinergic effects.
| Onset | Duration | Bioavailability |
|---|---|---|
| Peak plasma concentration (Tmax) occurs within 1-4 hours after oral administration. Clinical improvement in symptoms may be observed within 1-2 weeks, with full therapeutic effect typically seen after 4-6 weeks of continuous therapy. | Approximately 24 hours, supporting once-daily dosing. | Approximately 48% following oral administration. Absorption is not significantly affected by food. |
2. Mechanism of Action
Amisulpride exhibits a unique dose-dependent dual action on dopaminergic pathways. At low doses, it selectively blocks presynaptic dopamine D2/D3 autoreceptors in the mesocortical and mesolimbic pathways. This blockade disinhibits dopamine release, increasing dopaminergic tone, which is theorized to improve negative symptoms (avolition, anhedonia, blunted affect) and mood. At high doses, it antagonizes postsynaptic D2/D3 receptors in the mesolimbic pathway, reducing dopaminergic hyperactivity associated with positive symptoms (hallucinations, delusions). Its high selectivity for D2/D3 receptors with negligible affinity for other neurotransmitter receptors underlies its atypical profile.
3. Indications & Uses
- Schizophrenia (particularly for predominant negative symptoms at low doses)
- Acute and chronic psychotic disorders (including positive symptoms at higher doses)
4. Dosage & Administration
Adult Dosage: Schizophrenia (Negative Symptoms): 50-300 mg/day, usually 50-100 mg once daily. Schizophrenia (Positive Symptoms): 400-800 mg/day in 2 divided doses, max 1200 mg/day. Dysthymia: 50 mg once daily.
Administration: Oral administration. Can be taken with or without food. Tablet should be swallowed whole with a glass of water. For doses above 300 mg/day, it is recommended to divide the dose into two (morning and evening). Consistent timing is advised.
5. Side Effects
Common side effects may include:
- Insomnia, anxiety, agitation
- Weight gain (less than with some other atypicals)
- Hyperprolactinemia leading to galactorrhea, gynecomastia, amenorrhea, sexual dysfunction (erectile dysfunction, decreased libido)
- Sedation (dose-related)
- Constipation, dry mouth, nausea
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Levodopa, Dopamine Agonists (e.g., Pramipexole) | Antagonistic effect; reduces efficacy of dopaminergic drugs. | Major |
| QT-prolonging drugs (e.g., Amiodarone, Sotalol, Quinidine, Erythromycin, Clarithromycin, Fluoroquinolones, Tricyclic Antidepressants) | Additive risk of QTc prolongation and cardiac arrhythmias like Torsades de Pointes. | Contraindicated/Major |
| CNS Depressants (Alcohol, Benzodiazepines, Opioids, Sedative Antihistamines) | Additive sedative effects, impaired alertness, and respiratory depression. | Moderate |
| Antihypertensives | Potentiation of hypotensive effects, especially orthostatic hypotension. | Moderate |
| Other Antipsychotics (typical and atypical) | Increased risk of EPS, sedation, and metabolic side effects. | Moderate |
7. Patient Counselling
- DO take the medicine exactly as prescribed by your doctor. Do not change the dose or stop suddenly.
- DO inform all your doctors and dentists that you are taking amisulpride.
- DO keep regular follow-up appointments for monitoring of blood tests, ECG, and weight.
- DONT consume alcohol while on this medication.
- DONT drive or operate heavy machinery until you know how this medicine affects you.
- DONT take any other prescription, over-the-counter, or herbal medicine without consulting your doctor.
8. Toxicology & Storage
Overdose: CNS depression (somnolence to coma), hypotension, EPS (including severe akathisia, dystonia), QTc prolongation, arrhythmias, seizures, respiratory depression. Symptoms are extensions of pharmacological effects.
Storage: Store below 30°C. Protect from light and moisture. Keep in the original blister pack or container. Keep out of reach and sight of children. Do not use after the expiry date printed on the pack.