Is valacyclovir safe? Measure) ?

I am m27. Never had chickenpox before, had chickenpox rashes yesterday. Doctor(dermatologist) put me on valacyclovir 1g 3x a day for 7 days. I just want to confirm that it's safe for the above mentioned duration? I have left ectopic kidney. Usg kidney was otherwise normal last December, i do get frequent urination sometimes but the kft and urine routine were normal. So my question is, i am drinking 4-5 litres of water to ensure enough hydration. Is there anything else i should do to make sure i dont get acute kidney injury? Can i take any medication for kidney along with it?(as a preventative measure)? Just wanted to make sure i don't end up with kidney issues :(. Too scared. Please guide me doctors. Thank you