Osmolality and pH of anti-asthmatic drug solutions

Mixtures of different drugs are frequently used in aerosol solution for treatment of asthma. These drugs have different pH and osmolality values as stock solutions. It has been suggested that acidity and osmolality interact in provoking bronchoconstriction and cough. Therefore, pH and osmolality of anti-asthmatic drug solutions and mixtures were measured in the nebulizer at 0, 1, 2, 5, 10 and 15 minutes of nebulisation, pH of fenoterol, ipratropium bromide, salbutamol and disodium cromoglycate ranged between 2.0 and 5.7 and did not change during nebulisation. Nearly all drug solutions were hypoosmolar and the osmolality increased during nebulisation with 11 to 62%. Therefore, it is suggested to dilute these drugs with saline 0.9% and to restrict nebulisation time to 10 minutes, since the most striking increase of osmolality was noted after 10 minutes.