Comparative Study of Chemical Stability of Two H₁ Antihistaminic Drugs, Terfenadine and Its In Vivo Metabolite Fexofenadine, Using LC-UV Methods

Table 1

Validation of LC-UV methods for determination of terfenadine (TER) and fexofenadine (FEX).

Parameter	TER	FEX
Retention time (min)	2.52	2.44
Internal standard (i.s.)	Amiodarone	Papaverine
Resolution (between the drug and the i.s.)	4.86	3.87
Linearity range (μg/ml)	10–60	10–100
Slope	0.014252	0.010192
SD of slope	0.00016	0.000090
Intercept	−0.004228	−0.003933
SD for intercept	0.006410	0.002020
R^2	0.9976	0.9996
SD of R^2	0.00066	0.00036
LOD (μg/ml)	0.42	1.35
LOQ (μg/ml)	1.28	4.09
Accuracy (% recovery)	98.21–101.96	98.39–102.01
Precision (RSD)
Intraday	1.01–1.78	0.57–1.78
Interday	1.04–1.97	0.86–1.85
System suitability (RSD for peaks areas)	0.87	0.61
Tailing factor	1.38	1.18