Acyclovir comes as a tablet, a capsule, and a suspension (liquid) to take by mouth. It is usually taken with or without food two to five times a day for 5 to 10 days, starting as soon as possible after your symptoms begin. When acyclovir is used to prevent outbreaks of genital herpes, it is usually taken two to five times a day for up to 12 months. Take acyclovir at around the same times every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take acyclovir exactly as directed. Do not take more or less of it or take it more often or for a longer time than prescribed by your doctor.

Shake the liquid well before each use to mix the medication evenly.

Your symptoms should improve during your treatment with acyclovir. Call your doctor if your symptoms do not improve or if they get worse.

Take acyclovir until you finish the prescription, even if you feel better. If you stop taking acyclovir too soon or skip doses, your infection may not be completely treated or may become more difficult to treat.

Before taking Acyclovir

• tell your doctor and pharmacist if you are allergic to acyclovir, valacyclovir (Valtrex), any other medications, or any of the ingredients in acyclovir. Ask your pharmacist for a list of the ingredients.
• tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: amphotericin B (Fungizone); aminoglycoside antibiotics such as amikacin (Amikin), gentamicin (Garamycin), kanamycin (Kantrex), neomycin (Nes-RX, Neo-Fradin), paramomycin (Humatin), streptomycin, and tobramycin (Tobi, Nebcin); aspirin and other nonsteroidal anti-inflammatory medications such as ibuprofen (Advil, Motrin), and naproxen (Aleve, Naprosyn); cyclosporine (Neoral, Sandimmune); medications to treat HIV or AIDS such as zidovudine (Retrovir, AZT); pentamidine (NebuPent); probenecid (Benemid); sulfonamides such as sulfamethoxazole and trimethoprim (Bactrim); tacrolimus (Prograf); and vancomycin. Many other medications may also interact with acyclovir, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if there is a possibility you may be dehydrated from a recent illness or activity, or if you have or have ever had problems with your immune system; human immunodeficiency virus infection (HIV); acquired immunodeficiency syndrome (AIDS); or kidney disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking acyclovir, call your doctor.
• if you are taking acyclovir to treat genital herpes, you should know that genital herpes can be spread through sexual contact even if you don't have blisters or other symptoms and possibly even if you are taking acyclovir. Talk to your doctor about ways to stop the spread of genital herpes and about whether your partner(s) should receive treatment.