Risk Factors, Incidence, and Outcomes of Neuroleptic Malignant Syndrome on Long-Acting Injectable vs Oral Antipsychotics in a Nationwide Schizophrenia Cohort.

INTRODUCTION Long-acting injectable antipsychotics (LAIs) are associated with multiple positive outcomes in psychosis, but it is unclear whether LAIs are associated with worse outcomes if neuroleptic malignant syndrome (NMS), a potentially lethal adverse effect, occurs. METHODS We used nationwide and nationally representative databases of healthcare encounters in Finland to study the incidence and outcome predictors of NMS in patients diagnosed with schizophrenia/schizoaffective disorder between January 01, 1972 and December 31, 2017. Using a nested case-control design, we also explored differences by antipsychotic formulation (LAI vs oral antipsychotic [OAP]) and class (first-generation antipsychotic [FGA] vs second-generation antipsychotic [SGA]). RESULTS One hundred seventy-two NMS cases and 1441 sex-, age-, and diagnosis-matched controls were included (age = 58.8 ± 13.1 years, males = 59.9%). Incidence of NMS was 1.99 (1.98-2.00) per 10 000 person-years. The likelihood of developing NMS did not differ by antipsychotic formulation (adjusted odds ratio [aOR]: 0.89, 95% confidence intervals [95% CI]: 0.59-1.33, for LAIs vs OAPs) or class (FGA-OAP vs SGA-OAP [aOR: 1.08, 95% CI: 0.66-1.76], FGA-LAI [aOR: 0.89, 95% CI: 0.52-1.53], SGA-LAI [aOR: 1.35, 95% CI: 0.58-3.12]). NMS risk factors included antipsychotic treatment change: increased number (odds ratios [OR]: 5.00, 95% CI: 2.56-9.73); decreased number/switch (OR: 2.43, 95% CI: 1.19-4.96); higher antipsychotic dose (>2DDDs-OR: 3.15, 95% CI: 1.61-6.18); co-treatment with anticholinergics (OR: 2.26, 95% CI: 1.57-3.24), lithium (OR: 2.16, 95% CI: 1.30-3.58), benzodiazepines (OR: 2.02, 95% CI: 1.44-3.58); and comorbid cardiovascular disease (OR: 1.73, 95% CI: 1.22-2.45). Within 30 days, 4.7% of cases with NMS died (15.1% within 1 year) without differences by antipsychotic formulation. NMS reoccurred in 5 of 119 subjects (4.2%), after a median = 795 (range = 77-839) days after rechallenge with antipsychotics. CONCLUSION NMS remains a potentially life-threatening risk, yet these results should further contribute to mitigate concerns about LAI safety regarding NMS onset or outcomes, including mortality.