Incident infection during the first year of treatment - A comparison of clozapine and paliperidone palmitate long-acting injection

Revealing the reporting disparity: VigiBase highlights underreporting of clozapine in other Western European countries compared to the UK

BACKGROUND

Pharmacovigilance studies indicate clozapine history is marked by adverse drug reactions (ADRs).

OBJECTIVE

In a 2021 article, the United Kingdom (UK) had >90 % of European clozapine-related fatal outcomes in VigiBase, the World Health Organization's pharmacovigilance database. Two possibly opposing hypotheses could explain this disparity: 1) fewer reported fatal outcomes in other Western European countries mainly reflect underreporting to VigiBase, and 2) the higher number of UK reports reflects higher real relative mortality.

METHODS

VigiBase reports from clozapine's introduction to December 31, 2022, were studied for ADRs and the top 10 causes of fatal outcomes. The UK was compared with 11 other top reporting Western countries (Germany, Denmark, France, Finland, Ireland, Italy, Netherlands, Norway, Spain, Sweden and Switzerland). Nine countries (except Ireland and Switzerland) were compared after controlling for population and clozapine prescriptions.

RESULTS

The UK accounted for 29 % of worldwide clozapine-related fatal outcomes, Germany 2 % and <1 % in each of the other countries. The nonspecific label "death" was the top cause in the world (46 %) and in the UK (33 %). "Pneumonia" was second in the world (8 %), the UK (12 %), Ireland (8 %) and Finland (14 %). Assuming that our corrections for population and clozapine use are correct, other countries underreported only 1-10 % of the UK clozapine fatal outcome number.

CONCLUSIONS

Different Western European countries consistently underreport to VigiBase compared to the UK, but have different reporting/publishing styles for clozapine-related ADRs/fatal outcomes. Three Scandinavian registries suggest lives are saved as clozapine use increases, but this cannot be studied in pharmacovigilance databases.

Infections associated with clozapine: a pharmacovigilance study using VigiBase®

Introduction: Clozapine is primarily reserved for treatment-resistant schizophrenia due to safety concerns associated with its use. Infections have been reported with clozapine, which may lead to elevated serum levels of the drug. However, the existing literature on this topic is limited. Therefore, we conducted a study using VigiBase® to investigate the potential over-reporting of infections associated with clozapine, to explore the presence of dose-dependency, and to investigate the underlying mechanism. Methods: Disproportionality analyses were performed using VigiBase to assess the association between clozapine and all types of infections, the association between clozapine-associated infections and neutropenia, the association between clozapine-associated infections and agranulocytosis, the dose-effect relationship between clozapine and infections, and the interaction between clozapine and the main strong CYP450 inhibitors using reports carried out until 11 April 2023. Results: A statistically significant signal of infections was observed with clozapine, as indicated by an information component of 0.43 [95% CI: (0.41-0.45)]. The most commonly reported infections were respiratory and gastrointestinal in nature. Neutropenia showed weaker association with clozapine-associated reports of infections compared to other clozapine-associated reports [X2 (1, N = 204,073) = 454; p < 0.005], while agranulocytosis demonstrated a stronger association with clozapine-associated reports of infections [X2 (1, N = 204,073) = 56; p < 0.005]. No evidence of dose-dependency was observed. Among the 17 tested CYP inhibitors, significant drug-drug interactions were found with clarithromycin, metronidazole, valproic acid, lansoprazole, omeprazole, amiodarone, and esomeprazole. Discussion: Our study revealed a significant safety signal between clozapine use and infections, predominantly respiratory and gastrointestinal infections. The co-administration of clozapine with valproic acid or proton pump inhibitors may potentially contribute to an increased risk of infection. Further vigilance is warranted in clinical practice, and consideration of therapeutic drug monitoring of clozapine in cases involving concomitant use of these drugs or in the presence of infections may be beneficial.

A case-control study of antipsychotic use and pneumonia-related mortality in the United Kingdom

BACKGROUND AND AIM

There is increasing evidence linking antipsychotic use with pneumonia, but limited evidence of an effect on pneumonia-related outcomes such as mortality. In this study, we aimed to examine the association of pneumonia-related death with specific antipsychotic exposure.

METHOD

Deaths analysed were those reported to a UK-based drug-related deaths database, the National Programme on Substance Abuse Deaths (NPSAD), between 1997 and September 2020. We conducted a case-control study with cases defined as pneumonia-related deaths and controls as cases with alternative causes of death. Cases were analysed by considering drugs detected at post-mortem (PM) and by drugs prescribed to the deceased at the time of their death with calculated odds ratios (ORs) adjusted to account for confounders.

RESULTS

There were 2467 PM cases and 40,128 controls; 1818 prescribed cases and 28,018 controls. Second generation antipsychotics (SGAs) were robustly associated with an increased risk of pneumonia-related death compared with those not prescribed or taking antipsychotics (PM detection adjusted OR [AOR] 1·34 [95% CI 1·15-1·55]; prescribed AOR 1·28 [95% CI 1·11-1·49]). First generation antipsychotics had no clear association with death from pneumonia (PM detection AOR 1·06 [95% CI 0·77-1·47]; prescribed AOR 0·91 [95% CI 0·71-1·17]). Amongst SGAs, olanzapine was associated with an increased risk of death due to pneumonia (PM detection AOR 1·49 [95% CI 1·22-1·82]; prescribed AOR 1·44 [95% CI 1·18-1·76]) as was quetiapine (PM detection AOR 1·34 [95% CI 1·07-1·66]; prescribed AOR 1·28 [95% CI 1·01-1·64]).

CONCLUSION

Olanzapine and quetiapine were found to increase the risk of pneumonia-related death in this NPSAD sample to a clinically important extent.

Reasons for admission to a general medical hospital for patients taking clozapine

BACKGROUND

Clozapine is associated with a diverse range of side effects. In addition, patients prescribed clozapine commonly suffer with medical comorbidities.

OBJECTIVES

This study aimed to characterise patients prescribed clozapine who required medical admission, understand reasons for admission, identify areas for interventions to prevent future admission and describe clozapine management during the inpatient stay.

DESIGN

We conducted a retrospective analysis of patients prescribed clozapine who were admitted to a general medical hospital in a 12-month period.

METHOD

Data were collected using electronic drug charts and notes.

RESULTS

In total, 114 clozapine patients were hospitalised. Twenty-eight patients (25%) were admitted because of infection, 12 (11%) were elective admissions and 12 (11%) had gastrointestinal problems. Most patients admitted were Black (54%) and half were female. Few changes were made to clozapine dosing on admission or during the inpatient stay. Most patients had been taking clozapine for many years at the point of admission, the majority were able to continue taking it for the duration of their medical treatment and were discharged on the same dose they were taking prior to admission. Clozapine plasma concentrations were not consistently measured with only 18 (16%) patients having one or more plasma concentrations determined during their admission. The median clozapine plasma concentration on admission was 0.48 mg/L (nor-clozapine 0.21 mg/L), with a range of 0.09 to 3.9 mg/L. Three patients were admitted to the intensive care unit during their admission; all were discharged on clozapine. Four patients died; one from lung adenocarcinoma, one bowel obstruction, one cardiac arrest and one chest sepsis. In total, 27 patients (23%) had their clozapine stopped on admission, 6 (22% of this group) unintentionally.

CONCLUSIONS

Our study found that the most common reason for admission for patients taking clozapine was infection. Plasma concentrations were not measured routinely despite clozapine having a narrow therapeutic index and enhanced potential for toxicity in the medically unwell patient.