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Lack of desensitization to aerosol pentamidine with long-term use
A Rawji1, L R Lee-Pack, K Favell
1Department of Medicine, Wellesley Hospital, University of Toronto, Ontario, Canada.
Objective:
To assess whether long-term exposure to aerosol pentamidine (AP) results in desensitization.
Study Design:
Phase I-A retrospective, two group comparative study. Phase II-A prospective intervention study.
Methods:
Patients were selected from a 5-year database of 1200 individuals infected with the human immunodeficiency virus (HIV) who received AP as prophylaxis for Pneumocystis carinii pneumonia (PCP). In phase I, serial pre- and post-AP spirometry data of 33 subjects with significant bronchospasm on initial exposure to AP, who thus received aerosol salbutamol (AS) as regular pre-AP premedication for over 18 months, were compared to 33 matched controls who did not use AS. In phase II, 13 of the original group of 33 patients who required regular AS consented to a follow-up AP treatment without AS premedication to examine the effects of discontinuing AS premedication.
Results:
Phase I: on their initial AP treatment without AS premedication, the drop in mean FVC, FEV1, and FEV1/FVC values post-AP therapy was significantly lower for the AS group compared to the control group. The mean FEV1/FVC value for the AS group was 84% pre-AP and dropped to 75% post-AP therapy. For the control group the corresponding FEV1/FVC values were 83% (pre-AP) and 79% (post-AP). After using AS as premedication for AP for 18 months, the AS group did not show any reduction in flow rates as the mean FEV1/FVC values were 77% (pre-AP) and 80% (post-AP). The values in the control group were 80 and 78%, respectively. In phase II, when the 13 subjects who needed regular AS premedication were exposed to AP without premedication with AS, the flow rates are reduced in the same magnitude as observed at initial exposure to AP.
Conclusions:
The results of this study show that the prevention of bronchospasm with AS premedication while receiving long-term AP administration is due to the bronchodilator effect of AS, as desensitization is not achieved after over 18 months of exposure. These findings support long-term regular premedication with AS in patients with documented AP-induced bronchospasm.