Piroxicam is a non-steroidal anti-inflammatory drug that is characterized by low solubility
and high permeability. The purpose of the study was to investigate the in vitro and
in vivo performance of the semi-solid dispersion prepared with Gelucire 44/14 and
Labrasol into hard gelatin capsules (GL) for enhancing the dissolution rate of the
drug. The results were evaluated by comparing with pure piroxicam filled into hard
gelatin capsules (PP) and a commercially available tablet dosage form containing a
piroxicam:beta-cyclodextrin complex (CD). The in vitro dissolution testing of the
dosage forms was performed in different media (simulated gastric fluid, pH 1.2; phosphate
buffers, pH 4.5 and 6.8; and water). Amongst the dosage forms, GL provided at least
85% piroxicam dissolution within 30 min in each of the media, behaving like a fast-dissolving
immediate release drug product. Oral bioavailability of 20 mg piroxicam in GL, CD,
and PP was compared after administration of a single dose to eight healthy volunteers.
Three treatments were administered in crossover fashion, separated by a washout period
of 2 weeks. Piroxicam was monitored in plasma by high-performance liquid chromatography.
The apparent rate of absorption of piroxicam from GL (Cmax=2.64 micrograms/ml, tmax=82.5
min) was significantly higher than that of the PP (Cmax=0.999 micrograms/ml, tmax=144
min) (P<0.05) and similar to that of CD (Cmax=2.44 micrograms/ml, tmax=120 min) (P>0.05).
The relative bioavailability values as the ratios of mean total AUC for GL relative
to PP and CD, were 221 and 98.6%. Piroxicam is characterized by a slow and gradual
absorption via the oral route and this causes a delayed onset of therapeutic effect.
Thus, plain piroxicam preparations are not indicated for analgesia. The results of
the in vivo study revealed that the GL dosage form would be advantageous with regards
to rapid onset of action, especially in various painful conditions where an acute
analgesic effect is desired.