Opal 20 Capsule contains Omeprazole 20 mg, a proton pump inhibitor (PPI) used to reduce gastric acid secretion. It is indicated for the treatment of gastroesophageal reflux disease (GERD), erosive esophagitis, Zollinger-Ellison syndrome, and peptic ulcer disease, including Helicobacter pylori eradication when used in combination therapy. Omeprazole acts by irreversibly inhibiting the H+/K+ ATPase enzyme system at the secretory surface of gastric parietal cells, thereby suppressing the final step of acid production. This results in decreased gastric acidity, promoting healing of ulcers and inflammation of the esophagus. Opal 20 Capsule is typically administered orally once daily before meals, with dosage adjustments based on clinical response and specific indications. It is generally well tolerated; however, potential adverse effects include headache, abdominal pain, nausea, diarrhea, and rare hypersensitivity reactions. Long-term use may be associated with risks such as vitamin B12 deficiency, hypomagnesemia, and increased susceptibility to gastrointestinal infections. Caution is advised in patients with liver impairment and those on concomitant medications metabolized via the cytochrome P450 system. Opal 20 Capsule should be used under medical supervision, ensuring appropriate diagnosis and monitoring to optimize therapeutic outcomes and minimize adverse effects.