What are the most common side effects of acyclovir?
Common side effects of acyclovir (used as tablets, topical cream/ointment, or IV in some settings) can include mild, short-lived stomach and skin reactions. Typical reports include nausea, vomiting, diarrhea, and headache, along with local or skin-related effects such as burning or irritation when the drug is used on the skin.
How do side effects differ by form (cream vs pills vs IV)?
With topical acyclovir, skin irritation at the application site is more common (such as burning, stinging, or redness). With oral use (tablets), gastrointestinal symptoms and headache are more frequently reported. With IV acyclovir, the overall side effect profile can include issues related to the infusion and more serious effects are more likely than with topical or oral forms.
When should side effects be treated as urgent?
Contact a clinician urgently if side effects suggest an allergic reaction (for example, rash with swelling of the face/lips, trouble breathing) or if you develop severe symptoms such as persistent vomiting, severe headache, confusion, or symptoms of kidney problems (for example, much less urine than usual). These concerns matter more with higher doses or IV treatment.
Can acyclovir affect the kidneys?
Acyclovir can cause kidney-related side effects in some people, especially at higher doses or in those who are dehydrated or have pre-existing kidney disease. Staying well hydrated and following the prescribed dosing schedule is important. If you develop reduced urination or unusual weakness while taking it, seek medical advice promptly.