Get emergency medical help if you have any of these signs of an allergic reaction to acyclovir: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
Acyclovir can harm your kidneys. This effect is increased when you also use certain other medicines, including: probenecid, antivirals, chemotherapy, injected antibiotics, medicine for bowel disorders, medicine to prevent organ transplant rejection, injectable osteoporosis medication, and some pain or arthritis medicines
Other drugs may interact with acyclovir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.