This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti-Viral Drugs, Subject name: Pharmacology
[{'content': 'Which of the following is drug of choice for CMV retinitis? \nSelect and explain. \nA. Acyclovir, B. Tenofovir, C. Ganciclovir, D. Abacavir', 'role': 'user'}, {'content': "Answer: C \nExplanation: Doc for CMV retinitis - Ganciclovir Other drugs used - Foscarnet, cidofovir Herpes simplex virus (HSV), Varicella zoster virus (VZV) - Acyclovir Anti HIV drugs - Tenofovir, Abacavir Ganciclovir: Activated intracellularly by virus specific thymidine kinase Due to poor oral absorption, bioavailability of ganciclovir is low (<10%) It's prodrug valganciclovir ,which is better absorbed orally, has replaced it for oral therapy Systemic S/E: Bone marrow depression Rash ,fever,vomiting Neuro psychiatric disturbances", 'role': 'assistant'}]