Pharmaceutical preparation containing a mixture of a bismuth citrate and an alginate and any reaction products obtained, especially bismuth alginate for the treatment of gastritis, reflux oesophagitis, duodenitis, dyspepsia and ulcer disease. The preparation causes eradication of Campylobacter such as Helibacter pylori (HP) and it further actively prevents the reflux of the stomach content. It may further contain one or more antibiotic substances in order to give higher and more stable eradication rate. A calcium compound, e.g. calcium chloride may be added to the reaction medium to create microencapsulation beads of calcium alginate acting as a slow-release coating. The preparation may further contain an agent such as sodium bicarbonate causing a neutralisation of the gastric acid milieu and a foaming effect.