Stability of Omeprazole Mixtures: Implications for Paediatric Prescribing

Background Commercial omeprazole paediatric mixtures are not available. The stability of omeprazole mixtures prepared from Probitor capsules or omeprazole powder has not been established. Aim To determine the physicochemical stability of two omeprazole mixtures, prepared from Probitor capsules or omeprazole powder BP, over a 45–day period under refrigeration or at room temperature, shaken or unshaken. Method Omeprazole 2 mg/mL mixtures were prepared using standard procedures by either emptying the contents of Probitor capsules or by adding omeprazole powder to preserved sodium bicarbonate 8.4% solution. Each formulation was stored in 100 mL amber glass bottles under refrigeration (2–8°C) or at room temperature (21 ± 2°C). One bottle of each formulation was shaken and the other not shaken, pH was measured and colour change determined using a visual scale. Omeprazole concentrations were measured using liquid chromatograph tandem mass spectrometry on Days 1, 7, 14, 28 and 46. Results Omeprazole 2 mg/mL mixture prepared from Probitor capsules was stable over 45 days when refrigerated and regularly shaken. When unshaken, the omeprazole concentration decreased rapidly over 7 days. Mixtures prepared from omeprazole powder had lower concentrations compared to the mixtures prepared from Probitor capsules, but tended to be more stable when stored at room temperature. Observed colour changes did not correlate with measured omeprazole concentrations and pH remained constant. Conclusion Omeprazole mixture prepared from Probitor capsules was stable over 45 days, when refrigerated and regularly shaken. Omeprazole concentration markedly decreased in the mixture prepared from omeprazole powder when refrigerated.