Aciclovir can be used to: Treat chickenpox and shingles Treat cold sores, genital herpes and other herpes simplex infections Stop these problems returning after you have had them Stop these problems in people whose immune system works less well, which means their bodies are less able to fight infections Do not take Aciclovir Tablets: If you are allergic to aciclovir or valaciclovir or any of the other ingredients of this medicine. Warnings and precautions: Talk to your doctor, pharmacist or nurse before taking Aciclovir Tablets: If you have kidney problems If you are over 65 years of age Possible side effects: Allergic reactions: If you have an allergic reaction, stop taking Aciclovir 800 mg Tablets and see a doctor straight away. The signs may include: Rash, itching or hives on your skin. Swelling of your face, lips, tongue or other parts of your body. Shortness of breath, wheezing or trouble breathing. How to take Aciclovir Tablets: Take this medicine by mouth. Dissolve the tablet in a glass of water and stir before drinking. If you prefer, the tablet can also be swallowed whole with a little water. Dosage form and route of administration of Aciclovir Tablets should be prescribed according to therapeutic indication and disease severity of each individual patient. How to store Aciclovir Tablets: Keep this medicine out of the sight and reach of children. Do not use this medicine after the expiry date which is stated on the blister and the carton. The expiry date refers to the last day of that month.