What symptoms does acyclovir cause?
Acyclovir (an antiviral used for herpes viruses) can cause side effects in some people. Common symptoms reported with acyclovir include:
- Nausea, vomiting, diarrhea, or stomach upset
- Headache and dizziness
- Fatigue or weakness
- Skin rash or itching
- Pain at the injection site (if given by injection)
What symptoms are signs of an allergic reaction?
Stop taking acyclovir and get urgent medical care if you develop symptoms of a possible allergy, such as:
- Swelling of the face, lips, tongue, or throat
- Trouble breathing or wheezing
- Hives or widespread rash
- Severe skin reactions
What symptoms suggest kidney problems?
Acyclovir can affect the kidneys, especially in people who are dehydrated, older, or have pre-existing kidney disease, or when doses are too high. Seek prompt medical attention if you notice:
- Much less urine than usual
- Swelling in legs/feet
- Severe back pain (flank pain)
- Confusion or extreme drowsiness
Staying well hydrated (as advised by a clinician) can help reduce risk.
What symptoms suggest nervous system side effects?
Some people report neurologic effects, which warrant contact with a clinician promptly. Symptoms may include:
- Tremor, agitation, or confusion
- Hallucinations
- Seizures
- Marked drowsiness
These are more likely in higher doses, kidney impairment, or older adults.
When do symptoms appear after starting acyclovir?
Side effects like stomach upset, headache, and dizziness can show up soon after starting. Kidney and nervous-system symptoms are more likely when there are risk factors (dehydration or kidney disease) and may emerge within the first days of treatment or after dose changes.
If you have new or worsening symptoms after starting acyclovir, contact your prescriber.
What symptoms could mean you should not keep taking it?
You should not continue acyclovir without medical advice if you have:
- Signs of an allergic reaction
- Severe rash
- Symptoms of kidney injury (very low urine, significant swelling, severe flank pain)
- Severe confusion or neurologic symptoms
If you tell me your symptoms, I can help you triage
If you share:
1) the symptoms you’re experiencing,
2) your acyclovir dose and whether it’s tablets, cream, or IV, and
3) your age and whether you have kidney disease,
I can help you understand which side effects they match and what level of urgency makes sense.