<s>[INST]Hello:I am a 57 year old female that had shingles on my eyelid and ruined my cornea 4 years ago.  The Ophthalmologist put me on 800mg of acyclovir for a maintenance dose now.  I am having abdominal pain and blood in my stools now.  I have had outbreaks if not on acyclovir.  Not sure what to do.  I have not had a shingles shot.[/INST]Acyclovir is known to cause abdominal pains. Talk to your doctor about modification of the dose or for addition of certain anti-hyperacidity medicines like pantoprazole. However, it is unlikely to cause the bloody stools. Rather it is more likely that you have got a bacterial infection along. The infection needs to be treated with antibiotics. Please get a stool routine microscopy test done and visit your doctor with the report. Based on that he will be able to administer proper antibiotics which are essential in such a case. Take Oral rely Chat Doctor. </s>