“…Thus, the term of pseudo first-order kinetics was given to these reactions. From the slopes of the straight lines, we could calculate the relevant degradation rate constant and half-life (t 1/2 ) for each degradation condition by applying the following equations ( Mourad et al, 2016 ; Gawad and Belal; 2017 ; Marzouk et al, 2022 ): logC t = logC 0 - kt/2.303 t 1/2 = 0.693/k where, C t and C 0 are RMD concentrations estimated at a given time t and at zero time, respectively, k is the apparent first order rate constant and -K/2.303 is the slope of the line. Fig.…”
“…Thus, the term of pseudo first-order kinetics was given to these reactions. From the slopes of the straight lines, we could calculate the relevant degradation rate constant and half-life (t 1/2 ) for each degradation condition by applying the following equations ( Mourad et al, 2016 ; Gawad and Belal; 2017 ; Marzouk et al, 2022 ): logC t = logC 0 - kt/2.303 t 1/2 = 0.693/k where, C t and C 0 are RMD concentrations estimated at a given time t and at zero time, respectively, k is the apparent first order rate constant and -K/2.303 is the slope of the line. Fig.…”
“…The degradation rate constants were calculated (Table 6) from the slopes of the straight lines according to log C = log C 0 -Kt/2.303; where, the slope of the line is −K/2.303 (here, K is the degradation rate constant) and C and C 0 are the drug concentrations measured at a given time t and at zero time (in hour), respectively. 19,20 The found rate constants can be used to determine the half-lives of the drug in stressed conditions as there is no reported data found in this field.…”
This study was aimed to investigate the degradation behavior and physicochemical stability of desvenlafaxine using reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) system. The chromatogram was developed on Eclipse XDB-C8 column (150 x 4.6 mm, 5μm). The eluents were monitored through a photo diode array plus (PDA+) detector at 210 nm using an isocratic method with a flow rate of 1.5 ml/min. Mobile phase composition was 30:70 v/v mixture of 0.1 % trifluoroacetic acid (TFA) in water and methanol. Forced degradation studies were performed on drug substance of desvenlafaxine as per International Conference on Harmonization (ICH) prescribed stressed conditions (Q1A(R2) and Q1B) using hydrolytic (acidic, basic, and neutral), oxidative and photolytic methods. The drug substance was found highly labile to acidic (0.5 N hydrochloric acid, 18.65 % degradation in 2 hours at 70°C), basic (1.0 N sodium hydroxide, 11.01 % degradation in 12 hours at 70°C) and oxidative (3 % hydrogen peroxide, 17.05 % degradation in 2 hours at 50°C) stressed conditions, but a great resistance was observed towards dry heat (maximum degradation 0.27 % in 10 days from ambient to higher temperature, 80°C), moist heat (maximum degradation 0.25 % in 2 hours at 80°C and 75 % relative humidity) as well as in photolytic degradation (maximum degradation 0.23 % in 10 days at UV light of 315 - 400 nm). A pseudo-first order kinetic was followed in acidic, basic and peroxide degradation methods which paved a way to calculate the half-life of the drug substance desvenlafaxine under ICH mentioned stressed conditions. The results were also statistically analyzed and the % RSD values were compared with recommended guidelines.
Dhaka Univ. J. Pharm. Sci. 20(2): 167-176, 2021 (December)
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