My son was diagnosed with shingles last week and prescribed with Famciclovir, 250mg x 3 times a day. He is 17 years old. There was no presenting rash. The diagnosis was on the basis that he had a headache that was recurring, had felt unwell with body aches and one little lump on hid head. The doctor checked the lump and made his diagnosis as shingles. Since starting the medication on Wednesday, 10th June, my son has become very constipated and now very nauseated with severe loss of appetite. There are 6 tablets left in the packet. Could the tablets be causing these new symptoms or is there a possibility the he has been misdiagnosed?