Table 4

Stability results of topiramate

Stability experiments

Storage conditions

Mean comparison sample conc. found (ng/ml)

Mean stability sample conc. found (ng/ml)

     % Mean change at  quality control level

Bench top

  Room temperature (28 hr)

30.213

31.221

 LQC    3.34

3089.321

3045.651

  HQC  -1.41

Process (extracted sample)

  Auto sampler           (72 hr)

31.254

29.965

  LQC   -4.12

3154.231

3170.112

  HQC   0.50

Freeze and thaw stability in plasma

 After 4th FT cycle at -70oC

30.012

31.111

  LQC   3.66

3089.685

3045.365

  HQC  -1.43

Long term stability in plasma

For 72 days at          -70o C

30.224

31.231

  LQC   3.33

1512.321

1552.632

  MQC  2.67

3055.321

3001.285

    HQC  -1.77

LQC   =  30 ng/ml,  MQC = 1500 ng/ml,  HQC = 3000 ng/ml