Inhaled corticosteroids in COPD and the risk of serious pneumonia


Abstract

Background Inhaled corticosteroids (ICS) are known to increase the risk of pneumonia in patients with chronic obstructive pulmonary disease (COPD). It is unclear whether the risk of pneumonia varies for different inhaled agents, particularly fluticasone and budesonide, and increases with the dose and long-term duration of use.

Methods We formed a new-user cohort of patients with COPD treated during 1990–2005. Subjects were identified using the Quebec health insurance databases and followed through 2007 or until a serious pneumonia event, defined as a first hospitalisation for or death from pneumonia. A nested case–control analysis was used to estimate the rate ratio (RR) of serious pneumonia associated with current ICS use, adjusted for age, sex, respiratory disease severity and comorbidity.

Results The cohort included 163 514 patients, of which 20 344 had a serious pneumonia event during the 5.4 years of follow-up (incidence rate 2.4/100/year). Current use of ICS was associated with a 69% increase in the rate of serious pneumonia (RR 1.69; 95% CI 1.63 to 1.75). The risk was sustained with long-term use and declined gradually after stopping ICS use, disappearing after 6 months (RR 1.08; 95% CI 0.99 to 1.17). The rate of serious pneumonia was higher with fluticasone (RR 2.01; 95% CI 1.93 to 2.10), increasing with the daily dose, but was much lower with budesonide (RR 1.17; 95% CI 1.09 to 1.26).

Conclusions ICS use by patients with COPD increases the risk of serious pneumonia. The risk is particularly elevated and dose related with fluticasone. While residual confounding cannot be ruled out, the results are consistent with those from recent randomised trials.

Discussion

Using a large population-based cohort of over 160 000 patients with COPD followed for up to 18 years, we found that ICS use is associated with a significant 69% increase in the risk of serious pneumonia, requiring hospitalisation or fatal. This risk was particularly increased with fluticasone, with a doubling of the rate, and dose dependent with doses of 1000 μg of fluticasone per day associated with a 122% increase. The risk with budesonide was comparatively much lower with an increase of 17% and no dose–response effect. These elevated risks disappeared within a few months of stopping the use of ICS.

Systemic corticosteroids have been associated with increased risks of pneumonia in patients with rheumatoid arthritis.26 ,27 In these patients, a dose–response increase in the risk of pneumonia was seen with doses of prednisone as low as ≤5 mg/day (RR 1.4; 95% CI 1.1 to 1.6),26 and as low as 7.5 mg or less (RR 2.3; 95% CI 1.2 to 4.4).27 It is then not unexpected that high doses of ICS have similar effects on the incidence of pneumonia, as 1000 μg of inhaled fluticasone is estimated to be equivalent to 10 mg per day of prednisone with systemic effects evaluated by suppression of serum cortisol.7

Our findings confirm the observations of several randomised trials of varying durations and doses. The 2-year INSPIRE and 3-year TORCH trials both studied high doses of fluticasone (1000 μg per day) and found HRs of pneumonia of 1.94 (95% CI 1.19 to 3.17) and 1.64 (95% CI 1.33 to 2.02), respectively,3 ,4 ,13 ,14 A 1-year trial of fluticasone 1000 μg/day found a higher increase in the risk (RR 3.1; 95% CI 1.3 to 7.3; our calculation),15 which is consistent with our findings of a somewhat higher early risk. Our results confirm the subgroup analyses of the meta-analysis, suggesting that the risk is particularly elevated with high doses and start at short durations of use.12 With respect to the effect of dose, the two trials that evaluated a lower dose of fluticasone (500 μg per day) for 1 year also found a close to twofold higher incidence of pneumonia at 1 year with fluticasone.16–18This is also consistent with the dose–response curve from our study, which shows an increase in risk with lower doses and a RR of 1.6 at 500 μg/day of fluticasone.

The findings for budesonide confirm the pooled analysis of several trials of budesonide that found no increased risk of pneumonia over 1 year (RR 1.05; 95% CI 0·81 to 1·37),19 and a meta-analysis that suggests a lower risk with budesonide compared with fluticasone.20 Our finding of a more moderate 17% increase in the rate of serious pneumonia is concordant with these trial data. Moreover, the risk of pneumonia did not increase with the dose of budesonide. Nevertheless, a concern remains with budesonide as a recent 1-year trial in COPD found increases in pneumonia adverse events with daily doses of 640 μg (RR 2.3; 95% CI 1.2 to 4.7) and 320 μg (RR 1.7; 95% CI 0.8 to 3.6), equivalent to 400 μg and 200 μg of fluticasone, respectively.28 Since the fluticasone–salmeterol combination was approved and therefore promoted for COPD during the time period under study while the budesonide–formoterol combination was not, it remains possible that those receiving the budesonide combination were more likely to have asthma rather than COPD and be at lower risk of pneumonia compared with subjects receiving the fluticasone–salmeterol combination. Furthermore, since a higher dose formulation was only available for the fluticasone–salmeterol combination, patients with more severe disease may have been more likely to have received a combination therapy containing fluticasone rather than budesonide. Therefore, data on this question from countries where budesonide has a greater market share would be a valuable addition to this evidence.

There is good evidence supporting the effect of ICS on human pulmonary host defence, acting through several biological pathways, such as an inhibitory action on macrophage functions, a decrease in cytokine production and nitric oxide expression, which may lead to a failure to control infection.29 ,30 Although there have been no studies directly comparing the effects of fluticasone and budesonide on host defence, differences are likely related to their contrasting pharmacokinetic and pharmacodynamic properties. Fluticasone is known to be more potent (ie, greater effect on intracellular steroid receptors), more lipophilic and has a longer half life than budesonide.29Accordingly, fluticasone has a better penetration at the site of action and a more prolonged effect. It is therefore not surprising that a greater risk of oropharyngeal side effects is found with fluticasone compared with budesonide.31 While high potency and lipophilicity can be positive features allowing a lower dose to exert the desired effect, these characteristics may adversely affect drug safety. Indeed, a more prolonged corticosteroid effect in the lungs and greater pulmonary retention will facilitate the local immunosuppressive action.32 ,33 Budesonide enters the lungs with a lower lipophilicity, dissolves more quickly into pulmonary fluids, leading to a reduced local effect because of a more rapid cleavage and passage into the systemic circulation.30

This study has strengths and some limitations. The size of the population-based cohort of over 160 000 patients observed over 18 years permitted the identification of over 20 000 cases of serious pneumonia, allowing precise estimates of the risk associated with the different ICS at several doses. In this study, we defined serious pneumonia as a hospitalisation with a primary diagnosis of pneumonia or death from pneumonia, but did not have proof that the diagnosis was based on radiographic findings as these are not recorded in the RAMQ databases. However, it is most likely that as a primary inpatient diagnosis, it was in fact supported by a radiographic finding. To address confounding by COPD severity, we adjusted for the number of prescriptions for respiratory medications other than ICS, and for exacerbations as measured by prescriptions for oral corticosteroids, antibiotics, as well as prior hospitalisations for pneumonia and COPD exacerbation. Yet, residual confounding arising from unmeasured covariates can still be present. Of most concern is the possibility that budesonide may have been preferentially prescribed to patients with a lower risk of pneumonia, such as those with asthma or less severe COPD. In this specific study, however, our main results, adjusted for differences in severity, are consistent with those of several randomised trials which are inherently free of confounding, albeit less powerful with smaller study populations. Exposure to ICS was measured from dispensed prescriptions so that one must assume that the drugs were actually taken. However, not taking these medications would actually tend to underestimate the true risk increase. The definition of COPD used to identify the patients in our cohort was not based on a physician diagnosis of COPD or objective criteria for the diagnosis of COPD, but rather on including only subjects who started using respiratory medications at the age of 55 years or later and excluding subjects with a prior asthma hospitalisation or who used asthma-specific medications such as nedocromil, ketotifen, cromolyn or antileukotrienes. Nevertheless, our definition likely captured some patients with asthma. One can expect that this would reduce the estimate of risk of ICS since ICS do not appear to increase the risk of pneumonia in patients with asthma.34 Our sensitivity analysis within subjects previously hospitalised for COPD found practically the same differences in estimates of risk for fluticasone and budesonide.

The dose–response effect with fluticasone that we found on the incidence of serious pneumonia, sustained over a long time, is important in the risk–benefit balance for patients with COPD. While ICS are clearly effective for the treatment of asthma, their effectiveness in treating COPD is still controversial.1 ,2 The fact that ICS are now commonly combined in a single device with a long-acting bronchodilator, the latter recommended earlier in COPD, has resulted in ICS now being used by over 70% of patients with COPD.2 Moreover, these combined medications most often contain high doses of ICS, as high as 1000 μg of fluticasone per day.3 ,4 Consequently, the widespread use of ICS at higher doses in patients with COPD, along with the elevated incidence of pneumonia in this age group and their uncertain effectiveness, impact on the risk–benefit profile of ICS in COPD.

In conclusion, high and low doses of fluticasone in patients with COPD are associated with an important increase in the risk of serious pneumonia, while the risk with budesonide is comparatively low, even at high doses, though it needs further examination in light of recent data and the possibility that patients receiving budesonide are inherently at lower risk of pneumonia than those prescribed fluticasone. Further investigations into why the two popular ICS fluticasone and budesonide have such different effects on the risk of pneumonia are warranted.

Source: BMJ Thorax.