Mohammed is a 39 year old male who has presented with repeated episodes of dyspepsia in recent months. There are no red flags such as weight loss, dysphagia, or vomiting. He has altered his diet and lifestyle significantly and also trialled a proton pump inhibitor (PPI) for the past month, but his symptoms still persist. Helicobacter pylori testing is arranged for which the result is positive and treatment is arranged. Which one of the following medications is generally not used in eradication therapy?