Risperidone

Risperidone (Belivon®, Rispen®, Risperdal® in the United States) is an atypical antipsychotic medication. It is most often used to treat delusional psychosis (including schizophrenia), but risperidone (like other atypical antipsychotics) is also used to treat some forms of bipolar disorder and psychotic depression.

Generally lower doses are used for autistic spectrum disorders than are used for schizophrenia and other forms of psychosis; risperidone has received a not approved letter from the FDA for use in Autism. 

Risperidone is now the most commonly prescribed antipsychotic medication in the United States.

Side effects
Common side effects include nausea, anxiety, dizziness, insomnia, low blood pressure, muscle stiffness, muscle pain, sedation, tremors, increased salivation and weight gain (it is not uncommon for patients taking risperidone over long periods to gain upwards of 50 pounds or even more). It has also been known to cause sexual dysfunction, and occasionally lactation in both genders, through effects on hormones such as estrogen and prolactin.

Like all antipsychotics, Risperidone can potentially cause tardive dyskinesia (TD), extrapyramidal symptoms (EPS), and neuroleptic malignant syndrome (NMS), although the risk is generally less than for the older typical antipsychotics.

For some personal reports of the effects of using risperidone for autism or Asperger's syndrome - occasionally beneficial especially at very low doses such as 0.5mg per day, but sometimes severely distressing even at low doses.

Pharmacology
Risperidone is a very strong dopamine blocker (antagonist); i.e., it inhibits functioning of postsynaptic dopamine receptors.

It reaches peak plasma levels quickly regardless of whether it is administered as a liquid or pills. The strong dopamine-blocking reaction is known to make some people feel nauseated if they do things that normally trigger the dopamine response, such as eat a pleasing meal or experience orgasm. Risperidone is metabolised fairly quickly so this potential for nausea subsides usually in two to three hours.

Current forms
Risperidone is available in the form of ordinary tablets, fast-dissolving tablets, and solution taken orally, and in the form of a long-lasting injection, known as Risperdal Consta. The latter is especially important, due to the high percentage of mentally ill persons (especially with schizophrenia) who are unable or unwilling to take daily medication orally because of their impaired ability to distinguish between reality and fantasy.

Risperdal is manufactured by Johnson & Johnson (NYSE: JNJ), which also makes Risperdal Consta in conjunction with Alkermes, Inc.

Safety risks
In 2004, the Committee for the Safety of Medicines (CSM) in the UK issued a warning that risperidone and another atypical antipsychotic, olanzapine, should not be given to elderly patients with dementia, because of an increased risk of cerebrovascular adverse events including stroke.