Risperdal Consta is a long-acting injectable form of risperidone, an antipsychotic medication. Unlike the oral version of Risperdal, which is taken daily, Risperdal Consta is given as an injection every two weeks, releasing medication slowly over that period. It’s FDA-approved for treating schizophrenia and for maintaining stability in bipolar I disorder, either on its own or alongside other mood-stabilizing medications.
How the Injection Works
The medication is packaged as tiny microspheres, essentially microscopic beads made from a biodegradable polymer that slowly dissolves in your body. The risperidone is embedded inside these beads, and as the polymer breaks down over weeks, the drug is gradually released into your bloodstream.
The release pattern is distinctive and has a practical consequence you should know about. After a single injection, less than 1% of the dose releases right away. Then there’s a three-week lag where almost no drug enters your system. The main release kicks in around week three, holds steady through weeks four to six, and tapers off by week seven. Because of that three-week gap, you’ll need to take oral risperidone (or another antipsychotic) for the first three weeks after your first injection. Once the injectable form reaches full release, the oral medication is stopped.
Why an Injection Instead of a Pill
The core advantage is consistency. With a pill taken daily, missed doses are common and can lead to fluctuating drug levels or relapse. An injection given every two weeks at a clinic removes the daily decision entirely. Observational studies have linked switching from oral antipsychotics to long-acting injectable risperidone with reduced hospitalization rates and improved outcomes, though it’s worth noting that randomized controlled trials involving stable patients have not consistently shown a clear advantage over oral risperidone. The benefit likely depends on your individual situation, particularly whether daily pill-taking has been a challenge.
What the Injection Feels Like in Practice
Risperdal Consta is injected into the gluteal muscle (the buttock) or the deltoid muscle (the upper arm). The injection is given by a healthcare provider, so you’ll visit a clinic or doctor’s office every two weeks. Injection sites are typically alternated between left and right sides to reduce discomfort at any one spot. The medication comes in three dose strengths: 25 mg, 37.5 mg, and 50 mg per injection.
How It Works in the Brain
Risperidone, the active drug in Risperdal Consta, blocks two types of chemical receptors in the brain: dopamine D2 receptors and serotonin 5HT2 receptors. Overactivity in the dopamine system is thought to drive many symptoms of psychosis, including hallucinations and delusions, while serotonin receptor blocking is believed to help with mood symptoms and may reduce some of the movement-related side effects that older antipsychotics are known for. The drug also affects adrenaline-related receptors and histamine receptors to varying degrees, which explains some of its side effects like drowsiness and dizziness.
Common Side Effects
Clinical trial data from a 12-week study in people with schizophrenia provides a clear picture of what to expect. The most frequently reported side effects, at the standard 25 mg dose, were:
- Headache: 15% of patients
- Parkinsonism (stiffness, slowness of movement, tremor): 8%
- Dizziness: 7%
- Dyspepsia (indigestion or stomach discomfort): 6%
- Pain in extremity: 6%
- Constipation: 5%
- Sedation: 5%
- Weight gain: 5%
- Akathisia (a restless, fidgety feeling that makes it hard to sit still): 4%
At the higher 50 mg dose, several of these side effects occurred more often. Headache reached 21%, parkinsonism climbed to 15%, dizziness to 11%, and akathisia to 11%. Dry mouth, which barely registered at the lower dose, affected 7% of people at 50 mg.
For people using Risperdal Consta for bipolar disorder, the side effect profile shifts somewhat. When used alongside a mood stabilizer, tremor was the most common issue at 24%, with parkinsonism at 15% and sedation at 7%. Weight gain appeared in about 5 to 7% of patients across both conditions.
Serious Risks to Know About
Risperdal Consta carries a boxed warning, the most serious type of safety alert. Elderly patients with dementia-related psychosis who take antipsychotic medications face an increased risk of death. Risperdal Consta is not approved for treating dementia-related psychosis.
Other serious but less common risks shared by antipsychotic medications in this class include metabolic changes (elevated blood sugar, cholesterol, and triglycerides), a potentially life-threatening reaction called neuroleptic malignant syndrome involving high fever and muscle rigidity, and tardive dyskinesia, a condition involving involuntary repetitive movements that can sometimes persist even after the medication is stopped. Risperdal Consta can also raise levels of a hormone called prolactin, which may cause menstrual changes, breast tenderness, or sexual side effects.
What Makes It Different From Other Long-Acting Injectables
Several long-acting injectable antipsychotics exist, but Risperdal Consta’s three-week lag period is a distinguishing feature. Some newer formulations don’t require oral supplementation at the start, which simplifies the transition. The every-two-week schedule is also more frequent than some alternatives that are given monthly or even every few months. For some people, this frequency is an inconvenience. For others, the more frequent clinic visits provide a built-in touchpoint with their care team, which can be its own advantage.