Question: what are the side effects of ranitidine in infants?
Answer: Your child may have stomach pain, feel sick (nausea) or be sick (vomit) or they may get diarrhoea or constipation (difficulty doing a poo). ... 
They may get headaches.
Your child may feel dizzy or light-headed when they stand up, or may faint. ... 
They may get a rash.