Risperdal (Risperidone). Dosage, Side Effects, Interactions
Risperidone is an atypical antipsychotic . It is used to treat schizophrenia and moderate to severe manic episodes associated with bipolar disorder . If aggression occurs in Alzheimer’s dementia patients, the active substance can also be used for short-term treatment if there is a risk that the patients could endanger themselves or others.
Children from the age of five and adolescents with below-average intellectual function or mental retardation can also be treated with risperidone for a short period (up to six weeks) if they show aggressive behavioral disorders and pharmacological intervention is necessary. However, drug treatment should only be part of a comprehensive therapy.
How Risperdal (Risperidone) works
Risperidone binds to serotonergic 5-HT 2 and dopaminergic D 2 receptors, thereby blocking the action of various neurotransmitters such as dopamine and serotonin in the brain. This reduces nervousness and inner restlessness and other symptoms, such as hallucinations and delusions, agitation and aggressiveness and certain reflexes.
The affinity for the serotonergic receptor is greater than that for the dopaminergic receptor. It is believed that risperidone therefore causes fewer extrapyramidal motor symptoms than other antipsychotics . The active substance is also quickly released from the receptor and interrupts the blockade. Presumably, this is another reason why risperidone has fewer adverse effects than other antipsychotics.
In addition, there is a slight affinity for other receptors such as alpha-1 and alpha-2 adrenergic receptors and H 1 -histaminergic receptors. The impact of this affinity is still unclear.
The active ingredient is quickly and completely absorbed in the digestive tract. After about one to two hours, the maximum plasma concentration is reached with a bioavailability of about 70%. The elimination half-life of risperidone is approximately 3 hours and that of its metabolites is 24 hours.
The active substance is metabolised in the liver to 9-hydroxy-risperidone, also known as palperidone, mainly by the cytochrome P450 enzyme CYP2D6. This metabolite acts pharmacologically similar to risperidone itself and is part of the antipsychotic fraction.
Individual patients may be so-called extensive or poor CYP2D6 metabolizers due to genetic variation. These patients metabolize the drug much faster or much slower. The dosage may need to be adjusted in these patients.
Dosage of Risperdal (Risperidone)
The active ingredient is available on the market as a film-coated tablet in dosages of 0.25 mg, 0.5 mg, 1 mg, 2 mg, 3 mg, 4 mg and 6 mg and as an oral solution with a dosage of 1 mg/ml. The dose depends on why the patient is being treated with risperidone. The active substance is not suitable for children and adolescents under the age of 18 with schizophrenia or mania , as there is no data on this. The dosage may need to be adjusted in patients with impaired liver or kidney function.
On the first day, a dose of 2 mg risperidone is started, which is increased to 4 mg on the second day. In most patients, the desired success is already achieved with 4 mg as a maintenance dose. However, the dosage can also be increased, but due to the lack of data it should not be more than 16 mg per day.
Elderly patients are given an initial dose of 0.5 mg twice a day, which can be increased in increments of 0.5 mg to 1 to 2 mg daily.
Similar to schizophrenia, the initial dose is 2 mg once daily. If necessary, the dosage may be increased by 1 mg per interval at intervals of at least 24 hours. The maximum daily dose is 6 mg.
In elderly patients, the dose should be started at 0.5 mg twice daily and increased by 0.5 mg at each interval to 1 to 2 mg twice daily.
Patients with Alzheimer’s dementia and persistent aggression
The recommended starting dose for these patients is 0.25 mg twice a day. Depending on individual needs, it can be increased in increments of 0.25 mg per day. There should be at least two days between adjustments. The recommended optimal dose is 0.5 mg twice a day, but doses up to 1 mg twice a day can also be helpful. The maximum duration of treatment is six weeks.
Behavioral disorders in children and adolescents between the ages of 5 and 18 can be treated from a body weight of 50 kg with a starting dose of 0.5 mg once a day. If the desired effect is not yet achieved, the dose can be adjusted by a maximum of 0.5 mg every other day. The average dose is between 0.5 and 1.5 mg.
Patients weighing less than 50 kg are initially given 0.25 mg once a day and increased by 0.25 mg every other day if needed. The average dose is 0.25 mg per day.
Side effects of Risperdal (Risperidone)
The spectrum of side effects of risperidone is diverse. The most common side effects include Parkinsonism , drowsiness and sedation, and headache and insomnia.
Depending on the dosage, akathisia (restlessness while sitting) can also occur. The metabolite paliperidone can also cause side effects. They are similar to the risperidone side effects listed here by frequency:
- Sedation and drowsiness (somnolence)
- fever (pyrexia)
- chest pain
- Weakness (asthenia)
- urinary incontinence
- Joint pain (arthralgia)
- back pain
- musculoskeletal pain
- muscle spasms
- skin rash
- stomach pain
- abdominal discomfort
- Vomiting, nausea, constipation, diarrhea
- dry mouth
- shortness of breath (dyspnoea)
- pharyngolaryngeal pain
- nosebleeds (epistaxis)
- stuffy nose
- blurred vision
- sleep disorders
- weight gain
- increased or decreased appetite
- flu ( influenza )
- ear infection
- urinary tract infection
- Sinus infection (sinusitis)
- upper respiratory tract infections
- Inflammation of the lungs (pneumonia).
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