Perseris: the monthly subcutaneous risperidone injection

Perseris is the brand name for a once-monthly subcutaneous (under-the-skin) injectable formulation of risperidone, FDA-approved for the treatment of schizophrenia in adults in 2018. It joined the family of risperidone-based long-acting injectables alongside Risperdal Consta (bi-weekly intramuscular) and the paliperidone family (Invega Sustenna, Invega Trinza, Invega Hafyera).

How the depot works

Perseris uses a polymer-based delivery technology called the Atrigen system. Risperidone is dissolved in a biodegradable polymer that, once injected under the skin, forms a solid depot when it contacts body fluids. The depot then slowly releases risperidone over the next month.

Notably, Perseris produces a small initial release of risperidone within hours of injection — enough to establish therapeutic blood levels relatively quickly. This is why no oral risperidone overlap is required, in contrast to Risperdal Consta which needs 3 weeks of oral overlap.

The injection

Perseris is unique among risperidone LAIs in being given subcutaneously (under the skin of the abdomen) rather than intramuscularly. The injection volume is relatively small. After injection, patients can feel and sometimes see a small lump under the skin where the depot has formed; this typically softens over the month as the polymer degrades.

Dosing

Perseris comes in two dose strengths, given monthly. Patients should be tolerant of oral risperidone before starting Perseris (typically a few days of oral risperidone is recommended to confirm tolerability), but no extended oral overlap is needed once the first Perseris injection is given.

Missed-dose protocols

The FDA labelling defines specific catch-up protocols depending on how many days have passed since the last injection. Briefly, a few days late is usually fine; longer delays may require a brief oral risperidone bridge.

Side effects

The side effect profile is essentially that of oral risperidone:

• Hyperprolactinaemia — risperidone (and therefore Perseris) is one of the strongest prolactin-elevating antipsychotics. Symptoms can include irregular periods, breast tenderness or discharge, sexual dysfunction.
• Weight gain and metabolic changes — moderate, less than olanzapine but real
• EPS — moderate, particularly akathisia (see EPS guide)
• Sedation — usually mild to moderate
• Orthostatic hypotension — modest
• Tardive dyskinesia with long-term use (see tardive dyskinesia)

Injection-site reactions

Subcutaneous injections in general have a higher rate of visible local reactions than intramuscular injections, because the depot sits closer to the skin. Common reactions include:

• A small palpable nodule at the injection site for the duration of the month
• Pain, redness, or itching at the injection site for several days
• Mild bruising
• Rare: more pronounced inflammation or persistent nodules

Alternating sides of the abdomen at each injection helps reduce local irritation.

Perseris vs Risperdal Consta

Both deliver risperidone. Practical differences:

• Dosing interval — Perseris is monthly; Consta is every 2 weeks
• Oral overlap — Perseris requires no extended oral overlap; Consta requires 3 weeks of oral risperidone
• Route — Perseris is subcutaneous (abdomen); Consta is intramuscular (deltoid or buttock)
• Visible nodule — Perseris produces a small visible/palpable lump at the injection site for the dosing interval

For new starts, the simpler initiation of Perseris is often preferred. For patients already stable on Consta, there is rarely a reason to switch.

Perseris vs Invega Sustenna

Invega Sustenna is the monthly LAI of paliperidone — the active metabolite of risperidone. Both are once-monthly. Some key differences:

• Invega Sustenna requires two loading doses but no extended oral overlap
• Perseris requires one starter injection and no extended oral overlap
• Invega Sustenna is intramuscular (deltoid or gluteal); Perseris is subcutaneous (abdomen)
• Drug profile is similar (risperidone vs its active metabolite)

Choice is often clinician preference, prior tolerance, and patient comfort with subcutaneous vs intramuscular injection.

Who Perseris fits

• Patients who tolerate oral risperidone and want a monthly LAI
• Patients who want to avoid the 3-week oral overlap required by Risperdal Consta
• Patients who prefer subcutaneous to intramuscular injection

Who might want alternatives

• Patients particularly bothered by visible injection-site nodules
• Patients with hyperprolactinaemia symptoms — aripiprazole-based LAIs (Abilify Maintena, Aristada) tend to be more prolactin-friendly
• Patients who want a longer dosing interval — Invega Trinza (every 3 months) or Aristada at the highest dose (every 2 months) may suit better

The bigger picture

Perseris represents an evolution in LAI design: simpler initiation, monthly dosing, and a subcutaneous route that some patients prefer. For the right patient, it offers many of the benefits of an LAI without the complications of older risperidone depots. As always, the right LAI is the one that fits the patient's biology, preferences, and life circumstances — a conversation that belongs in the prescriber's office.

This article is for educational purposes only and is not medical advice. Information is summarised from publicly available FDA labelling and peer-reviewed literature. Always consult your prescribing clinician before starting, stopping, or changing any medication. If you or someone you know is in crisis, call or text 988 in the US, or your local emergency number.