Administration of an alginate based gastric reflux suppressant on the bioavailability of omeprazole

Omeprazole treats gastro-oesophageal reflux disease (GORD) by inhibition of acid secretion whereas alginate based reflux suppressants work by forming a low density raft of near neutral pH which floats on the stomach contents and physically impedes gastro-oesophageal reflux. There is limited pharmacokinetic information regarding possible drug interaction between these two types of products, although these may be frequently co-prescribed to improve symptom control in GORD patients. This study was designed to determine whether the administration of a 10 per cent w/v liquid alginate suspension affected the pharmacokinetic profile of omeprazole.

This was a randomized, two-treatment, two-sequence, two-period crossover study in 26 volunteers. Each treatment was dosed for 3 consecutive days with a washout period of 7 days between dosing periods. Blood samples for pharmacokinetic analysis were taken over the 24 h period following the final dose of omeprazole.

Geometric means and ratios were as follows: C(max) was 555 for omeprazole/alginate and 558 for omeprazole alone (ratio 99.55%, 90% confidence interval 82.75-119.75%; AUC(0-t) was 2050 for omeprazole/alginate and 2094 for omeprazole alone (ratio 97.90%, 90% confidence interval 87.83-109.12%); AUC(0-a) was 2247 for omeprazole/alginate and 2231 for omeprazole alone (ratio 100.74%, 90% confidence interval 90.05-112.70%). Mean values for T(max), K(el) and T(1/2) were also similar for the two treatment regimens.

As the 90 per cent confidence intervals for the geometric mean ratios for C(max), AUC(0-t), and AUC(0-alpha) are all contained within the bioequivalence interval of 80-125 per cent, it can be concluded that the administration of this liquid alginate suspension does not affect the pharmacokinetic profile of omeprazole.