B. Wichert et P. Rohdewald, LOW-MOLECULAR-WEIGHT PLA - A SUITABLE POLYMER FOR PULMONARY ADMINISTERED MICROPARTICLES, Journal of microencapsulation, 10(2), 1993, pp. 195-207
Citations number
NO
Categorie Soggetti
Pharmacology & Pharmacy","Chemistry Applied","Engineering, Chemical
Beclomethasonedipropionate (BDP)-containing microparticles were prepar
ed by the solvent evaporation/extraction method. Different preparation
parameters were optimized before investigations. Polylactic acid (PLA
) and polylactic/glycolic acid (PLGA) with molecular weights of 2000 a
nd 15 000 were used as matrix polymers. In all experiments the mean di
ameter of the microparticles was 1-5 mum with a drug content greater-t
han-or-equal-to 23 per cent. Microparticles of PLA, MW 2000, showed a
prolonged and complete release over 8 h, whereas those of PLGA liberat
ed only 20 per cent of the encapsulated drug within 8 h. BDP was deter
mined by a validated reversed-phase HPLC method with a detection limit
of 20 ng/ml. The encapsulated steroid seemed to be dissolved within t
he polymer, as differential scanning calorimetry suggested. Considerin
g mean particle size, drug load, release characteristics and the statu
s of the drug inside the matrix, the dosage form showed very good char
acteristics for inhalatory application. Surface characteristics of the
microparticles were visualized by scanning electron microscopy (SEM).
Although in vitro studies with human bronchial fluid resulted in a st
rong deterioration of microparticles, main structures were still visib
le by SEM after an incubation of 36 h in diluted bronchial fluid ex vi
vo. Degradation in phosphate buffered saline, protein solution and eve
n in port liver esterase suspension resulted in minor effects on the p
article surface.