A nurse is reinforcing teaching with a client who has a new diagnosis of shingles and is prescribed acyclovir. Which client statement indicates understanding of when to begin antiviral therapy?

I can begin the medication anytime during the outbreak for the same effect.

I should take the medication only if the pain becomes severe.

I should wait until the blisters scab over before starting the medication.

I should start the medication within 72 hours of the rash appearing.