Osmolality changes in nebulizer solutions

Paradoxical effects (bronchoconstriction instead of bronchodilatation) have been reported after inhalation of beta2-mimetics in asthmatic children, and it has been suggested that this was due to osmolality and pH changes of the nebulizer solution. We tested commercially available nebulizer solutions and found osmolality changes after 5, 10 and 15 min of nebulization. Osmolality was measured in the nebulizer chamber and the airsteam of two types of jet nebulizers. When normal saline was nebulized chamber, from 282 +/- 7 mmol.kg-1 to 432 +/- 18 mmol.kg-1 resulted. Salbutamol ready made solution, and terbutaline respules were isotonic, whereas fenoterol, disodium cromogylcate (DSCG), beclomethasone dipropionate (BDP) and salbutamol (respirator solution 0.5%) were hypotonic (60-100 mmol.kg-1). When a mixture of sodium chloride (NaCl) and the drug solution (salbutamol, terbutaline, fenoterol) was nebulized for 10-15 min, the osmolality in the nebulizer cup increased to 420-500 mmol.kg-1. However, mixtures of the same beta 2-agonists with DSCG or with BDP remained hypo-osmolar. The same osmolality changes were present in the airstream. This study shows that after 10-15 min of nebulization osmotic changes occur in the nebulizer cup and airstream and that these changes differ according to the drug mixtures and the amount of the solution in the nebulizer chamber.

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