95 - Risperidone intramuscular long acting injecti

Risperidone intramuscular long-acting injections

Schizophrenia and related psychoses CHAPTER 1 Risperidone long-­acting injection In this section we give brief details on the range of risperidone LAIs (RLAIs) available around the world in 2024. We have done our best to identify each formulation by some unique property and by a trade name. These trade names do vary somewhat by country. Readers are directed to formal product information for full details of each formulation. Risperidone intramuscular long-­acting injections Risperdal Consta – risperidone 2-­weekly long-­acting injection RLAI is now very rarely initiated in practice and here we give no information on starting doses or its therapeutic uses. It has been superseded by longer-­acting risperidone and paliperidone injections with less complex pharmacokinetic profiles. Here we provide information on stopping RLAI and on switching to other formulations. In doing this, we have relied upon the following assumptions:1 Weeks after last injection 4 Consta injection given 0 10 20 2 6 Weeks Active moiety (ng/ml) 10 First missed dose Second missed dose Figure 1.1  Blood levels following discontinuation of treatment with 25mg every 2 weeks: last ­injection at week 4. Source: reproduced with permission from Wilson (2004).2 Timescale of plasma concentrations after last dose of RLAI 4–5 weeks Peak plasma concentration from last dose reached 6 weeks Plasma levels fall below threshold for therapeutic effect 7–8 weeks Plasma concentrations approach zero Switching from RLAI is complicated because, in regular dosing, plasma concentrations remain therapeutic for around 6 weeks following the last injection. Two weeks after the last injection (i.e. the time of the first missed injection) plasma levels are yet to peak and will in fact reach a peak on two occasions after this time (Figure 1.1).

100 The Maudsley® Prescribing Guidelines in Psychiatry CHAPTER 1 Table 1.23 provides general recommendations when switching from RLAI. These suggestions are aimed at ensuring that, when switching someone who is responsive to RLAI, a therapeutic plasma concentration of the new antipsychotic is established before risperidone concentrations become sub­therapeutic. A further aim is to ensure that therapeutic levels of the new drug will be maintained during the first dosing interval. Rykindo® Rykindo is a 2-­weekly injectable suspension of risperidone given in the gluteal muscle to patients who have previously responded and tolerated risperidone.8 After IM injection risperidone blood concentration peaks at 14 days and reaches steady state after two administrations. Oral supplementation is required for the first 7 days of treatment. The recommended starting dose is 25mg every 2 weeks, with a maximum dose of 50mg every 2 weeks. Dose adjustments can be made every 4 weeks. Patients on Consta can switch directly to Rykindo without needing oral supplementation. The first IM injection should be given 4–5 weeks after the last Consta administration (refer to Table  1.25 later in this section for equivalent doses). Like Consta, Rykindo must be stored in the refrigerator and allowed to sit at room temperature for at least 30 minutes before reconstitution. The reconstitution process is similar to that for Consta. Please refer to manufacturer’s advice for further details. Table 1.23  Switching from risperidone long-­acting injections.3,4 Switching to Recommended method of switching Comments Oral risperidone Start oral tablets 4–5 weeks after the last RLAI injection 25mg/2 weeks = 2mg/day 37.5mg/2 weeks = 3mg/day 50mg/2 weeks = 4 mg/day5 Oral antipsychotic (not risperidone) Start oral antipsychotic 4–5 weeks after the last RLAI injection Monitor for adverse effects Paliperidone LAI6 Initiate the equivalent dose of the paliperidone LAI in place of the next scheduled dose of RLAI, then continue monthly administration (a second loading dose is not required and should not be given) 25mg/2 weeks = 50mg/monthly 37.5mg/2 weeks = 75mg/monthly 50mg/2 weeks = 100mg/monthly Risperidone ISM®* (Okedi, Risvan, and others)7 Initiate the equivalent dose of risperidone ISM in place of the next scheduled dose of RLAI and continue risperidone ISM at 28-­day intervals 37.5mg/2 weeks = 75mg/28 days 50mg/2 weeks = 100mg/28 days Aripiprazole LAI Start oral aripiprazole 4–5 weeks after the last RLAI dose. Initiate ALAI 2 weeks after starting oral aripiprazole. Note that aripiprazole LAI can be initiated in two ways. For more information refer to the relevant section of this book and manufacturer’s advice. Antipsychotic LAI (not paliperidone or risperidone ISM) Start the new LAI 4–5 weeks after the last RLAI For some LAIs, oral trial and/or test dose may be required to establish response and tolerability * Formal recommendations recommend giving risperidone ISM in place of the next RLAI injection; i.e. 2 weeks after the last injection. A 4-­week interval makes more sense because risperidone ISM will then be given shortly before the time of peak plasma levels from the last RLAI injection.