Flucloxacillin causes heartburn, nausea, and vomiting by irritating gastric mucosa if taken empty stomach. Stress also predisposes gastric irritation causing stress ulcer in stomach. Gastric irritation causes secretion of gastric juice which contains hydrochloric acid which is responsible for hunger pain. Advice 1. Take flucloxacillin after taking some snacks with full one glass of water 2. Ranitidine 150 mg every 12 hours for 5 days 3. Avoid smoking and alcohol for few days if you are consuming 4. Do not eat heavily at a time. Divide your meals into smaller portions and eat them frequently during the day 5. Avoid eating 3 hours before lying down 6. Raise the head of your bed 7. Avoid spicy foods, fatty foods, mint, chocolate, tomato-based foods, coffee, and citrus fruits Thanks