Problems with parsimony in sequences of biased base composition

In almost all eradication regimens, which contain antibiotics and bismuth derivatives, the administration of acid suppressing drugs for 4-6 weeks is recommended for healing of duodenal ulcer. The aim of this multicenter double blind study is to elucidate the effect of two classic antibiotics tetracycline (CAS 60-54-8) and metronidazole (CAS 443-48-1) alone or combined with ranitidine (CAS 66357-35-5) on the healing of duodenal ulcer and eradication of Helicobacter Pylori. Patients with duodenal ulcer were randomized to two treatment groups: group A received either ranitidine 4 x 150 mg or tetracycline 4 x 500 mg or metronidazole 3 x 250 mg for 2 weeks. Group B received 4 x placebo + tetracycline and metronidazole as in group A for 2 weeks. A final endoscopy was performed after 8 weeks. Four biopsy specimens were obtained from the antrum (two) and corpus (two) for both urease test and hematoxylin stain for detection of H. pylori. Out of 201 patients entering the study 156 completed the study (78 in A and 78 in B). The healing rate of duodenal ulcer was 98.7% in group A and 97.5 in group B. The eradication rate was only 33.3% in group B but 64% in group A (p < 0.001), when additionally ranitidine was given. The present study shows that treatment with the two antibiotics tetracycline and metronidazole alone results in a very low H. pylori eradication, but almost complete healing of duodenal ulcer after 8 weeks. Prolonged administration of antisecretory drugs in eradication regimens containing two antibiotics is not necessary for duodenal ulcer healing. However, the addition of H2-receptor antagonists or proton pump inhibitors to antibiotics increases the eradication rate.