Time (mins) At pH 4 % Availability (mean ±  S.D) At pH 9 % Availability (mean ±  S.D) Lef Flur Lef Flur 0 100.06 ± 0.21 99.99 ± 0.27 100.02 ± 0.35 100.06 ± 0.09 30 100.5 ± 0.42 101.01 ± 0.22 98.04 ± 0.61 107.97 ± 0.81 60* 100.72 ± .51 102.65 ± 0.13 102.4 ± 0.51 103.25 ± 0.57 90* 99.89 ± .13 105.8 ± 0.61 100.12 ± 0.43 99.99 ± 0.26 120** 98.33 ± .71 113.52 ± 0.99 102.14 ± 0.76 101.7 ± 0.49 150**+ 96.38 ± .19 117.55 ± 0.42 104.28 ± 0.27 102.58 ± 0.94 180**++ 93.38 ± 18 131.62 ± 0.51 99.86 ± 0.772 105.88 ± 0.21   Lef Ibu Lef Ibu 0 100.1 ± 0.98 100.01 ± 0.74 100.25 ± 0.98 99.97 ± 0.11 30 97.98 ± 0.510.29 98.15 ± 0.26 100.39 ± 0.57 98.04 ± 0.52 60 98.09 ± 0.34 98.68 ± 0.13 104.18 ± 0.64 102.75 ± 0.41 90* 99.031 ± 0.32 98.2 ± 0.27 104.09 ± 0.26 103.46 ± 0.49 120* 103.33 ± 0.23 99.3 ± 0.53 103.53 ± 0.94 102.91 ± 0.75 150**++ 101.35 ± 0.24 97.9 ± 0.49 105.89 ± 0.25 103.07 ± 0.64 180**++ 103.64 ± 0.19 96.6 ± 0.21 108.69 ± 0.16 104.74 ± 0.28   Lef Diclo Lef Diclo 0 100.1 ± 0.23 100.15 ± 0.74 100.02 ± 0.64 99.99 ± 0.51 30* 101.33 ± 0.54 104.9 ± 0.16 99.89 ± 0.91 99.29 ± 0.42 60**+ 102.16 ± 0.86 110.11 ± 0.98 99.29 ± 0.83 95.60 ± 0.26 90**+ 101.4 ± 0.64 111.85 ± 0.23 102.79 ± 0.43 105.78 ± 0.54 120**+ 107.25 ± 0.35 110.15 ± 0.34 99.89 ± 0.71 97.65 ± 0.19 150**++ 110.19 ± 0.46 125.2 ± 0.56 102.46 ± 0.43 99.04 ± 0.18 180**++ 112.12 ± 0.28 126.67 ± 0.47 105.23 ± 0.22 101.58 ± 0.29       Lef Mef 0 - - 100.91 ± 0.23 100.04 ± 0.43 30 - - 100.7 ± 0.52 100.65 ± 0.61 60 - - 100.61 ± 0.16 100.01 ± 0.78 90 - - 101.13 ± 0.14 101.27 ± 0.98 120 - - 101.51 ± 0.09 100.27 ± 0.15 150 - - 101.99 ± 0.21 102.05 ± 0.11 180* - - 102.78 ± 0.84 101.99 ± 0.31 Lef=leflunomide, Flur=flurbiprofen, Ibu=ibuprofen, Mef=mefanamic acid, Diclo=diclofenac sodium. * and ** indicates p< 0.05 (significant) and p< 0.005 (highly significant) at pH 4 while + and ++ indicates p< 0.05 (significant) and p< 0.005 (highly significant) interaction at pH 9

Table 8: Interaction study of leflunomide with NSAIDs by proposed RP- HPLC method.