A study of people aged 65 or over in the Netherlands showed that people taking antipsychotic drugs had an increased risk of pneumonia, compared with those who had been treated with antipsychotics in the past.

Previous studies have found an association between antipsychotic drug use and pneumonia in hospitalised patients.

In this study, Dr Gianluca Trifiro and colleagues from Erasmus University Medical Centre, Rotterdam, analysed patient record data from a Dutch general practice research database.

They identified 2,560 elderly patients who were given a first antipsychotic drug prescription during the 10-year follow-up period. During this time, 264 patients contracted community-acquired pneumonia. Twenty-one per cent of these patients were hospitalised as a result, and a further 25 per cent died.

Researchers compared these patients with pneumonia with a control group of 1,689 people without pneumonia. They assessed timing of drug use, type, and dose of antipsychotic between the two groups.

Patients using atypical anti-psychotics were 2.6 times as likely to suffer pneumonia compared with those in the control group who had taken antipsychotic drugs in the past. Typical antipsychotic drugs were associated with a 1.8 times higher risk of pneumonia.

The authors suggested the anticholinergic action and H1-receptor-blocking effect of antipsychotic drugs may offer an explanation for the occurence of pneumonia.

They said H1-receptor blocking, which causes sedation and difficulty swallowing, may facilitate aspiration pneumonia.

The authors concluded: 'Clinicians who start treatment with both atypical and typical antipsychotic drugs should closely monitor patients, particularly at the start of therapy and if high doses are given, with respect to the risk for community-acquired pneumonia.'

• Ann Intern Med 2010; 152: 418.