Detection and determination of free and plasma protein-bound astemizole by thin-layer chromatography: a useful technique for bioavailability studies.
A thin-layer chromatographic (TLC) procedure has been developed for the determination of astemizole in plasma as the free and as protein-bound substance. The detection and quantification were performed without using internal standards. In earlier described methods for the estimation of astemizole by high-performance liquid chromatography and radioimmunoassay, only free levels in plasma were quantified, at 3.3% of the total astemizole, with the remaining 96.7% bound to plasma protein and tissue. Our method employs proteolysis of plasma proteins by incubating plasma for 2 h in pepsin. After proteolysis the astemizole is extracted, and a known amount of the extract is spotted on precoated silica gel F 254 plates. Astemizole was quantified using a Shimadzu CS-930 dual-wavelength TLC scanner. The method provides a direct estimate of total astemizole present in the plasma.
R & D Centre, Cadila Laboratories Ltd., Ahmedabad, India.
S
S
Mangalan
R B
RB
Patel
T P
TP
Gandhi
B K
BK
Chakravarthy
D000818:Animals; D016589:Astemizole / Q000097:blood* / Q000493:pharmacokinetics; D001682:Biological Availability; D001798:Blood Proteins; D002855:Chromatography, Thin Layer; D004285:Dogs; D006801:Humans; D008297:Male; D011485:Protein Binding; D011863:Radioimmunoassay; D012996:Solutions
D001798:Blood Proteins; D012996:Solutions; D016589:Astemizole