Can Valtrex cause Viral Pharyngitis? I have 5 tiny canker sore like ulcers on one tonsil. Symptoms appeared two days after starting pill.

No, Valtrex does not. cause viral pharyngitis. Most likely, the sores you are seeing are from the infection you are treating with the Valtrex. The Valtrex takes some time to begin working & the sores may have already been starting at a sub clinical level. If they are continuing, please see your doctor.