The dose emission characteristics of eight marketed dry powder inhaler
s (DPIs: Intal Spinhaler(R), Ventolin and Becotide Diskhalers(R), Vent
olin and Becotide Rotahalers(R), Bricanyl and Pulmicort Turbohalers(R)
, Berotec Inhalator(R)) have been investigated using the proposed USP
dosage unit sampling apparatus for DPIs. Intra- and inter-device varia
tion in emitted doses was determined at air flow rates of 60 and 100 l
/min using a 4 lair throughput in each case except Inhalator(R), which
was tested at 30 l/min only. The sampling apparatus was found to be s
uitable for quantifying single emitted doses from all of these devices
which comprise examples of low, medium and high airflow resistance DP
Is (Table 1 footnote). Dose emissions from the DPIs are presented as p
ercentages of the manufacturers' label claims. Under all test flow con
ditions variability was high, when compared to the uniformity of conte
nt standards usually applied to pharmaceutical products; in some cases
relative standard deviations (RSD) were greater than 15%, both within
and between devices. However, under the proposed USP test flow rate c
onditions, the total RSD (n = 25) was < 15% around the average emitted
dose in all cases except Pulmicort Turbohaler(R); such variance (RSD
< 15%) is proposed to be acceptable for DPIs delivering current medica
tions. Only the Intal Spinhaler(R) emitted an average dose similar to
its label claim. Testing at 100 l/min vs 60 l/min significantly increa
sed DPI drug emission and reduced the device retention of both the Ven
tolin(R) and Becotide(R) versions of the low resistance devices, Rotah
aler(R) and Diskhaler(R). Using these same flow rates for testing the
dose emissions from the medium resistance Bricanyl and Pulmicort Turbo
halers(R), there was no significant difference in drug output between
the two flow rates.