Aerosolized Pentamidine and Spontaneous Pneumothoraces in AIDS Patients
We were quite interested in the six cases of spontaneous pneumothoraces reported by Martinez et al. We have not experienced any episodes of spontaneous pneumothorax in our AIDS patients in either of our two secondary prophylaxis aerosolized pentamidine studies.
From June 1, 1988 to December 31, 1988, there have been 55 patients involved in our double-blind randomized, placebo-controlled trial comparing treatment with pentamidine vs placebo for secondary prophylaxis of Pneumocystis carinii pneumonia (PCP). Since the study is still in progress, we do not know the exact number of individuals on pentamidine therapy. However, after eight months of prophylactic treatment, no spontaneous pneumothorax has been detected. These patients were clinically assessed on a monthly basis, had complete pulmonary function tests on a bi-monthly basis, and had chest radiographs (CXR) at baseline and at six months.
In another study (an open-labelled trial which was initiated in October, 1988) we have 14 patients on aerosolized pentamidine therapy for secondary prophylaxis of PCP During the first two months of this study, none of the 14 individuals developed spontaneous pneumothorax.
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Aside from our formal trials, we have one patient who developed three episodes of spontaneous pneumothorax and one episode of pneumomediastinum while he was on secondary prophylactic therapy with aerosolized pentamidine. The patient obtained his own supply of pentamidine and the dosage was 60 mg every two weeks. The nebulizer used was obtained through a US source and was a FISONeb. However, it should be pointed out that all four episodes occurred in the setting of early relapse of PCP. Therefore, it is difficult to attribute the cause of pneumothorax/pneumomediastinum to aerosolized treatment because they may be due to concurrent PCP.
The reason for the “alarming number of pneumothoraces” experienced by Martinez et al is unclear. However, the authors might help the readers by providing the following information: 1) How many patients were treated (ie, the denominator for calculation of the occurrence rate of spontaneous pneumothorax)? 2) Were all the episodes of pneumothorax clinically relevant or were they detected by a routine surveillance protocol? 3) What was the dose of pentamidine and the type of nebulizer, and how often was the drug administered? 4) What was the frequency of cough and broncho- spasm with aerosolized treatment?
The dosage of pentamidine in both our studies is 60 mg per treatment. We administer five loading doses over a two-week interval, followed by a maintenance dose at bi-weekly intervals. The nebulizer used in these studies is a FISONeb ultrasonic nebulizer (Fisons Corp, Bedford, MA). In our open trial, the frequency of cough/bronchospasm as detected by spirometry was about 14 percent. These episodes were generally mild and responded well to inhaled bronchodilator. viagra jelly
We suspect that the ultrasonic nebulizer used may be the principal cause for the development of spontaneous pneumothorax. However, if that were true then one would expect a direct correlation between the occurrence of spontaneous pneumothorax and the frequency of cough/bronchospasm.
We agree with Martinez et al that continued pulmonary surveillance is both necessary and important in patients on prophylactic aerosolized pentamidine treatment.