Angiotensin converting enzyme (ACE) inhibitors protect against the development of pneumonia, research suggests.
A meta-analysis of 37 studies found the risk of pneumonia was cut by around a third with ACE inhibitors compared with control treatment.
There was no such effect with angiotensin receptor blockers (ARBs), the analysis showed.
Writing in the British Medical Journal, the Portuguese researchers said the results could discourage the withdrawal of ACE inhibitors due to cough – a side effect which they believe might actually underpin the apparent protection against pneumonia.
The risk of pneumonia was also reduced in patients treated with ACE inhibitors who were at higher risk of pneumonia, in particular those with stroke and heart failure.
Combining data from eligible studies showed a 34% reduction in pneumonia risk with ACE inhibitors compared with control treatment and a 31% reduced risk compared with ARBs.
Among Asian patients there was a 57% decreased risk compared with non-Asian patients.
The researchers said more studies are needed to work out the full clinical effect suggested in the study, and to determine why the effect seemed so strong in Asian populations.
The team from the Portuguese Cochrane Centre said prescriptions of ACE inhibitors may be influenced by concerns about adverse reactions such as cough, when in reality an enhanced cough reflex may be protective.
‘Our results suggest that patients taking ACE inhibitors who develop cough should, providing that cough is tolerable, persist with treatment,' they concluded.
They also said a possible reduced risk of pneumonia may influence choice of ACE inhibitor over ARB.
‘In the case of a particular patient, in whom ACE inhibitors and ARBs are presumed to have similar clinical benefit, our results may also influence the choice of prescription in those at high risk of pneumonia.'
But in an accompanying editorial, Professor Rosemary Barnes, Cardiff University School of Medicine, said it was too early to take the step of using ACE inhibitors for the prevention of pneumonia.
She said that although the review seemed to support the theory that the cough which is commonly a side effect of ACE inhibitors helped to protect the respiratory tract against pneumonia, the findings should be interpreted with caution.
‘Is it right on the basis of this study to recommend that patients should put up with their resistant cough because it could reduce their risk of pneumonia?' Professor Barnes questioned.
‘This is an important clinical question, but to agree would run counter to current evidence based guidelines that recommend discontinuation.'
Professor Barnes concluded a better understanding of the pharmacology underpinning the possible effects was needed before ‘we advise patients to put up with their cough because it may prevent them from getting pneumonia'.
Professor João Costa, professor of clinical pharmacology at the Portuguese Cochrane Centre, and author of the study, said: ‘A fair message that can be drawn based on our conclusions is that if a physician is considering either ACE inhibitoror ARB for an individual patient and that individual patient is at high risk for pneumonia, then ACE inhibitorsis probably a best treatment option.'
