Research Article
Comparative Study of Chemical Stability of Two H1 Antihistaminic Drugs, Terfenadine and Its In Vivo Metabolite Fexofenadine, Using LC-UV Methods
Table 3
Percentage degradation and kinetic parameters of terfenadine (TER) and fexofenadine (FEX) under UV/VIS irradiation at different pH.
| | Stress conditions | Degradation (%) | Linear equation y = ax + b | R2 | k (min−1) | t90 (h) | t50 (h) |
| | TER | | pH 4.0 | 39.32 | y = −0.0142x + 3.9932 | 0.9656 | 5.45 × 10−4 | 3.21 | 21.19 | | pH 7.0 | 35.32 | y = −0.0131x + 3.9365 | 0.9861 | 5.03 × 10−4 | 3.48 | 22.96 | | pH 10.0 | 41.06 | y = −0.0145x + 3.8755 | 0.9811 | 5.56 × 10−4 | 3.14 | 20.77 | | FEX | | pH 4.0 | 43.64 | y = −0.0175x + 3.9115 | 0.9756 | 6.72 × 10−4 | 2.60 | 17.19 | | pH 7.0 | 39.14 | y = −0.0145x + 3.8787 | 0.9706 | 5.56 × 10−4 | 3.14 | 20.77 | | pH 10.0 | 45.42 | y = −0.0167x + 3.9118 | 0.9795 | 6.41 × 10−4 | 2.73 | 18.02 |
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