MRI-documented muscular lesion associated with paliperidone palmitate: case presentation and a pharmacovigilance-based case-non-case analysis

Paliperidone palmitate is one of the most prescribed long-acting injectable antipsychotics in clinical practice. in this report, we discuss one of its reletively common side effects, i.e. site injection pain, which is often ovelooked by clinicians but may reduce patients’ compliance to treatment. We report the case of a 46-year-old sinhalese man with schizophrenia who was treated with paliperidone palmitate for two years with an increasing site injection pain symptomatology investigated with magnetic resonance imaging, which revealed a considerable muscular lesion. We conducted a case-non case analysis based on the italian pharmacovigilance database in order to frame our case in a larger context. this study shows how local reactions associated with our drug of interest have a reported odds ratio of 3.54, with a 95% confidence interval between 1.89 and 6.62. Our results indicate a disproportionality between the presentation of injection site effects in paliperidone palmitate compared to the other drugs of a similar class. Realistically, specific histopathological studies on the differences between injection site reactions in distinct atypical antipsychotics are essential to improve understanding of these mechanisms in terms of chemical/cellular interactions, and to provide new insight in controlling the foreign body response and in designing the next generation of long-acting injectable antipsychotics.