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Table 1 Hydrolysis rate of DMF to MMF and half-lives of DMF in different environments. To analyze under which circumstances DMF can be hydrolyzed to MMF and whether MEF affects the hydrolysis of DMF into MMF, we determined the hydrolysis rates for DMF in different environments. In short, a 0.1 M sodium phosphate buffer, human serum and whole blood (all pH 7.4) were spiked with either 2 mg/L of DMF or with the combination of 2 mg/L of DMF and 1.4 mg/L of MEF and at several intervals thereafter, samples were taken and prepared in order to measure the concentration of DMF, MMF and MEF by HPLC. Subsequently, after calculating the area under the curves for DMF (AUC_DMF) and MMF (AUC_MMF), the following model [16] was used to fit the concentrations of MMF and to estimate the kDMF (rate of hydrolysis of DMF into MMF) in these solutions: [MMF]t = i = (kDMF*AUC_DMF)-(kMMF*AUC_MMF) + [MMF]t = 0. In addition, the half-life was calculated using the following formula: t1/2 = ln(2)/k. Data are means and SD (n = 3). # and * significant (p < 0.05) different value between buffer and and serum and serum and whole blood, respectively.

From: In vitro pharmacokinetics of anti-psoriatic fumaric acid esters

  kdmf (h-1) t1/2 (h)
Buffer   
Spiked with:   
DMF 0.06 (0.004) 12.72 (1.04)
DMF+MEF 0.05 (0.01) 15.17 (1.88)
Serum   
Spiked with:   
DMF 1.96 (0.47) 0.37 (0.08) #
DMF+MEF 2.20 (0.25) 0.32 (0.05) #
Whole blood   
Spiked with:   
DMF 8.01 (3.78) 0.10 (0.04)*
DMF+MEF 10.08 (2.74) 0.07 (0.02)*