Hi Cathy, Thanks for your query and sorry to hear about your son’s condition. I have read your question and understand your concern. In your son’s case, lethargy can be due to a number of factors such as, his original diagnosis (which is not yet clear), chest infection, being bed ridden for 6 weeks, low mood (which is quite significant), being on Vent, derangements in various body salts (electrolytes) etc. Meropenem, which is a strong antibiotic can also cause tiredness but it should not be solely held responsible for the problem. Therefore, I would recommend that you talk to his treating physician/s who should conduct a thorough assessment, which would include clinical examination and investigations, to find out the cause behind his tiredness. If necessary, meropenem can be replaced or other necessary support (psychological with/out medications) be commenced. Things are not simple for you but with proper plan a way forward can be sought. Hope this helps.