As with any disease, the amount of medicine required for treating herpes zoster, depends upon the severity and the extent of the eruption. Generally in an uncomplicated, usual case, antiviral for 7-10 days is more than enough. Comorbid conditions may necessitate additional medicines. The patient is potentially infective, till the last blister dries up. Generally the doctor is well versed with the side-effects of the medicines he/she has prescribed. The patient is reviewed periodically to see if the response is as expected and also for any side-effects which the patient maybe unaware of. Therefore visit your doctor as and when he/she calls you.