Terfenadine reacts with mixed anhydriedes (Malonic and acetic anhydrides)
producing a yellow-coulored product with intense fluorescence. Based on this
fact, a spectrophotometric method was developed for the determination of
terfendaine in dosage f
orms. The relation between the absorbance at 395 nm and
the concentration is rectilinear over the range 0.5-5 μg.ml-1. The reaction product
was also measured spectrofluorimetrically at 435 nm after excitation at 395 nm.
The fluorescence intensity was directly proportional to the concentration over the
range 0.5-4 ng.ml-1. The different parameters affecting the development and
stability of the reaction product were carefully studied and incorporated into the
procedure. The proposed spectrophotometric method was successfully applied to
the determination of terfenadine in tablets and suspensions; the % recoveries
were 99.83 ± 0.75 and 99.65 ± 0.83, respectively. The proposed
spectrofluorimetric method was applied to the determination of terfenadine in
spiked human plasma. the % recovery was 99.35 ± 2.19. The method is highly
sensitive and specific. No interference was noticed from co-formulated drugs,
such as pseudoephedrine and ibuprofen.
