Safety of incremental inhaled lipopolysaccharide challenge in humans.

Background: Inhalation of environmental endotoxin is important in the pathogenesis of asthma and other environmental airway diseases. Inhaled airway challenge using lipopolysaccharide in humans has been performed for over 20 years to assess the airway response to endotoxin. However, there are no published data on the short-term safety of endotoxin inhalation protocols.

Objective: To characterize the safety and tolerability of incremental inhaled lipopolysaccharide challenge in humans.

Patients And Methods: We performed a retrospective analysis of data obtained from 119 subjects who underwent inhaled challenge with up to 41.5 mug of lipopolysaccharide. We measured pulmonary function, temperature, mean arterial pressure, heart rate, and systemic symptoms for 3 h after challenge.

Results: Fever occurred in 30% of subjects and was associated with a higher cumulative dose of lipopolysaccharide. Reduced mean arterial pressure occurred in 21% of subjects and was dose-related. There was no association between fever or decreased mean arterial pressure and airway responsiveness to inhaled lipopolysaccharide. Common symptoms reported by subjects included: chills (64%), malaise (56%), cough (56%), chest tightness (49%), headache (43%), and myalgias (27%). None of the subjects experienced delayed discharge or a serious adverse event.

Conclusions: Inhaled lipopolysaccharide causes dose-related systemic responses that include fever, reduced blood pressure, and constitutional symptoms that are not associated with the airway response to inhaled lipopolysaccharide. Systemic responses to inhaled lipopolysaccharide should be expected and subjects undergoing inhaled lipopolysaccharide challenge in the research setting should be carefully monitored for non-pulmonary adverse events for several hours after challenge.