A novel method for assessing dissolution of aerosol inhaler products.

Glucocorticoids administered by inhalation remain a first-line treatment of patients with asthma allergic rhinitis and advanced chronic obstructive pulmonary disease. Budesonide (BD), fluticasone propionate (FP) and triamcinolone acetonide (TA) have high hepatic first-pass inactivation of the swallowed fraction of the inhaled dose, whereas there is no first-pass metabolism in the lung. Hence, the lung bioavailability will determine the overall systemic absorption and the systemic bioactivity. Efficacy of inhaled agents in the respiratory tract depends on the site of deposition and physicochemical properties of the drug, which dictates rate of dissolution, absorption, metabolism and elimination. However, to date no official method exists for testing dissolution rates from inhalation aerosols. An in vitro flow through dissolution method may be useful to provide information on rate of release and determine formulation differences between products or in product development. After administration of three glucocorticoids into a cascade impactor they underwent dissolution in a flow through cell utilising water, simulated lung fluid (SLF) and modified SLF with L-alpha-phosphatidylcholine (DPPC) as a dissolution medium, at constant flow and temperature. Modified SLF significantly increased the dissolution rate compared with SLF alone. This novel technique appears to be a useful method of evaluating dissolution of these glucocorticoids and may also be applied to other respiratory products administered via aerosols.