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Mark Lyons MPharm
Clinical Pharmacist
South London and Maudsley NHS Trust
David Taylor BSc MSc PhD MRPharmS
Director of Pharmacy and Pathology
South London and Maudsley NHS Trust
Until 2002 only depot formulations of typical antipsychotics (flupentixol, fluphenazine, haloperidol, pipotiazine and zuclopenthixol) were available. These depots, as with their oral formulations, were associated with a high risk of extrapyramidal side-effects (EPSE) and tardive dyskinesia (TD), but nevertheless gained widespread use. The introduction of the atypical antipsychotics promised an increased patient acceptability with a lower incidence of EPSE and TD. This article reviews the three atypical antipsychotics that are available for use in Europe: paliperidone palmitate (PP); olanzapine long-acting injection (OLAI); and risperidone long-acting injection (RLAI).
Paliperidone
Pharmacology
Paliperidone (9-hydroxyrisperidone) is the most recent atypical antipsychotic to become available as a depot. It binds strongly to dopaminergic D2 and serotonergic 5-HT2 receptors and also exerts adrenergic 1, and histaminergic H1 receptor blockade.
Pharmacokinetics
Paliperidone is available as an aqueous nanosuspension of the palmitate ester. It can be administered four-weekly because of its very poor water solubility (and so slow dissolution) and resultant long half-life (T
