Is Low Body Mass Index a Risk Factor for Postinjection Delirium/Sedation Syndrome?

Sir, Nonadherence to oral antipsychotics is one of the greatest problems affecting treatment outcomes in patients with schizophrenia.[1] Long‐acting injection (LAI) formulations of antipsychotics were introduced with the objective of reducing noncompliance. Olanzapine LAI was Food and Drug Administration approved in 2010. A rare but potentially serious side effect of olanzapine LAI is postinjection delirium/sedation syndrome (PDSS). The risk factors for the development of PDSS are unclear. We report a case of a 29‐year‐old single male who presented with a 9‐year history of a continuous psychotic syndrome. He had been treated several times in the past but was noncompliant with oral antipsychotic drugs. The patient was admitted with a diagnosis of paranoid schizophrenia. On physical examination, his body mass index (BMI) was 19. After 4 weeks of treatment with oral olanzapine, he was given olanzapine LAI. About 45 min after receiving the injection, the patient became drowsy. He was confused and disoriented. He was unable to stand without support and was mumbling incoherently. He did not have fever or rigidity. Blood investigations were within normal limits. A diagnosis of PDSS was made. His vital signs and urine output were closely monitored. He was given intravenous fluids and supportive care. He recovered completely within 17 h after the injection. A causality assessment was done using the Naranjo adverse drug reaction probability scale,[2] and a score of 5 was obtained indicating that olanzapine LAI was the probable cause for PDSS. It has been hypothesized that accidental entry of olanzapine LAI into the bloodstream can cause rapid dissolution of olanzapine pamoate into olanzapine and pamoic acid. This results in very high concentrations of olanzapine in the bloodstream causing PDSS.[3] However, even taking adequate precautions in the method of administering the drug does not reliably prevent the occurrences of PDSS. This suggests that there are other contributing factors that cause PDSS. Our patient had a BMI of 19 kg/m2 which maybe a risk factor for the development of PDSS. Previously, it has been suggested that a low BMI and old age could be possible risk factors.[4] Further research is needed to determine the risk factors and preventive measures of PDSS.