Oral Primary herpes simplex infections Adult: 200 mg 5 times daily every 4 hr for 5-10 days; for severely immuno compromised patients and those with impaired absorption: 400 mg 5 times daily for 5 days. Suppression of recurrent herpes simplex Adult: 800 mg daily in 2-4 divided doses. May reduce to 400-600 mg daily if necessary. Reassess the condition every 6-12 mth. For mild or infrequent recurrences: Episodic treatment may be used: 200 mg 5 times daily for 5 days, preferably begun during the prodromal period. Prophylaxis of herpes simplex in immunocompromised patients Adult: 200-400 mg 4 times daily. Varicella zoster 800 mg 5 times/day for 5-7 days. Herpes zoster 800 mg 5 times/day for 7-10 days.