Risperdal (Risperidone) Side Effects: Common and Rare

Risperdal (risperidone) is an atypical antipsychotic drug approved by the U.S. Food and Drug Administration (FDA) to treat schizophrenia, mania with bipolar I disorder, and irritability in children and adolescents with autism spectrum disorder. If you've been prescribed this medication, it's important to be aware of the potential side effects before starting treatment.

Overview of Risperidone

Risperdal is a brand name for the generic drug risperidone. Under the brand name, this medication is available in several forms: oral tablets, liquid solutions, or injectable suspension.

The oral dose of risperidone generally ranges between 1 mg and 6 mg per day, with injectable dosage ranges between 12.5 mg and 50 mg daily. In most cases, people begin at a low dose that is gradually increased until the desired therapeutic effects are achieved.

Several of Risperdal's properties can lead to side effects. Since it is antihistaminic, for instance, it may be sedating. As an alpha-adrenergic blocker, it can interfere with hormones that regulate blood flow and blood pressure.

Risperidone also has anticholinergic effects that alter the function of smooth muscles. These are the muscles that make up the internal organs.

Common Side Effects of Risperdal

The most common side effects of Risperdal, which were reported in more than 10% of the clinical trials involving this drug, included:

• Abdominal pain or discomfort
• Anxiety
• Constipation
• Cough
• Dizziness
• Drowsiness or sleepiness
• Dry mouth
• Excessive salivation
• Fatigue
• Fever
• Increased appetite
• Involuntary muscle contraction
• Nasal congestion, runny nose, and sneezing
• Nausea and vomiting
• Rash
• Tremors or slow, rigid movements
• Upper respiratory tract infection
• Urinary incontinence

Extrapyramidal Side Effects of Risperidone

Extrapyramidal side effects (EPS) can affect as many as one of every four people who take risperidone, although most cases are relatively mild. These side effects affect the central nervous system and cause movement problems.

Other than a previous history of EPS, there is no way to know in advance whether you'll experience these effects. There are several types of EPS that are associated with atypical antipsychotic drug use, along with a few factors that can impact your risk levels.

Types of EPS

An estimated one in five people taking atypical antipsychotics like risperidone experience a type of EPS called tardive dyskinesia. This potentially irreversible disorder is characterized by involuntary and repetitive movements, including those of the face, mouth, tongue, arms, or legs.

Other types of EPS that may be experienced with antipsychotic drugs include:

• Akathisia: a feeling of inner restlessness and inability to stay still, often referred to as the "rabbit syndrome"
• Akinesia: a loss or impairment of voluntary movement
• Dystonic reactions: intermittent and involuntary contractions of the muscles in the face, neck, trunk, pelvis, and extremities
• Parkinsonism: a group of neurological disorders that cause movement problems similar to Parkinson's disease, including tremors, slow movement, and stiffness

Risk Factors

If you take a high dosage of risperidone, the likelihood of developing EPS appears to increase. For example, one eight-week trial found that 15% of subjects taking 2 milligrams of Risperdal experienced Parkinsonism compared to 31% of subjects taking 16 milligrams of this drug.

If you are on this drug for an extended period, your risk of EPS may also increase. Though it's important to know that, while rare, you can still develop EPS when taking Risperdal at lower doses or for short periods.

Rare But Serious Side Effects of Risperdal

On rare occasions, exposure to atypical antipsychotics can result in a potentially life-threatening reaction. Here are some to watch for.

Neuroleptic Malignant Syndrome

Neuroleptic malignant syndrome (NMS) is a condition that occurs in 0.01% to 0.02% of people taking antipsychotic medications and is characterized by the following symptoms:

• Altered mental state
• High blood pressure or blood pressure fluctuations
• High fever (over 100.4 F)
• Loss of bladder control
• Muscle rigidity
• Profuse sweating
• Respiratory problem
• Seizures
• Tachycardia (rapid heartbeat)

If NMS occurs, symptoms generally appear within two weeks of starting the drug. Factors that appear to increase the risk of NMS include exhaustion, dehydration, and malnutrition, with young adult males and people who have organic brain syndromes or intellectual disabilities being affected most often.

Additional Serious Side Effects

Other rare but potentially life-threatening side effects that may occur with Risperdal use include:

• Diabetic ketoacidosis (a dangerous build-up of acids in the blood)
• Pancreatitis (inflammation of the pancreas)
• Pulmonary embolism (the formation of a blood clot in the lungs)
• Seizures
• Stroke
• Sudden cardiac death
• Suicide attempts

Elderly patients with dementia-related psychosis have a higher risk of death when taking antipsychotic drugs—4.5% versus 2.6% in individuals taking a placebo or sham drug. Risperdal is not approved as a treatment for this condition, so it should not be taken for this purpose.