An enteric coated oral pharmaceutical formulation comprising as active ingredient a compound selected from the group of omeprazole, an alkaline salt of omeprazole, the (-) enantiomer of omeprazole and an alkaline salt of the (-) enantiomer of omeprazole, wherein the formulation comprises a core material of the active ingredient and optionally an alkaline reacting compound, the active ingredient is core material a separating layer and an enteric coating layer. A hydroxypropyl methylcellulose (HPMC) of low viscosity with a specific cloud point is used in the manufacture of pharmaceutical formulations. Furthermore, the application describes the processes for their preparation and use of the claimed formulations in medicine.