Overview
Risperidone is an atypical antipsychotic used to treat schizophrenia and bipolar disorder. It works primarily by antagonizing dopamine D2 and serotonin 5-HT2A receptors, helping to reduce psychotic symptoms and stabilize mood. The extended-release injectable formulation provides sustained delivery over two weeks, improving adherence in maintenance therapy.
Mechanism of Action
Risperidone is a monoaminergic antagonist with high affinity for serotonin 5-HT2A, dopamine D2, α1 and α2 adrenergic, and H1 histaminergic receptors. Its antipsychotic effects are primarily mediated through combined dopamine and serotonin receptor antagonism, which helps regulate neurotransmitter imbalances associated with psychosis and mood disorders.
Indications
- Treatment of schizophrenia
- Monotherapy for maintenance treatment of bipolar I disorder
- Adjunctive maintenance treatment for bipolar disorder
Common Doses
- 25 mg
- 37.5 mg
- 50 mg
Dosage
Extended-release injectable suspension administered every 2 weeks by deep intramuscular injection in deltoid or gluteal muscle. Initial oral tolerability testing recommended. Dosing typically starts at 25 mg or 50 mg every 2 weeks, adjusted based on clinical response and tolerability.
Contraindications
- Known hypersensitivity to risperidone, paliperidone, or any excipients in the formulation
Side Effects
- Headache
- Parkinsonism
- Dizziness
- Akathisia
- Fatigue
- Constipation
- Dyspepsia
- Sedation
- Weight increased
- Pain in extremity
- Dry mouth
- Tremor
- Agitation
- Depression
- Anxiety
- Hyperglycemia
- Hypokinesia
Interactions
- Drug interaction data based on oral risperidone studies; systematic evaluation of extended-release injectable formulation interactions not completed
- Potential interactions with other CNS depressants, antihypertensives, and drugs affecting CYP2D6 and CYP3A4 metabolism
Counseling Points
- Administer every 2 weeks by healthcare professional only
- Report symptoms of neuroleptic malignant syndrome (fever, muscle rigidity)
- Monitor for signs of tardive dyskinesia (involuntary movements)
- Regular monitoring of weight, blood glucose, and lipids recommended
- Avoid sudden position changes to prevent orthostatic hypotension
- Report difficulty swallowing or prolonged painful erections immediately
- Inform healthcare provider if pregnant or planning pregnancy