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Abstract
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.