Acyclovir is an antiviral medication that is used to treat herpes infections. Like any medication, acyclovir can cause side effects. According to Drugs.com [2], some of the common side effects of acyclovir include nausea, vomiting, diarrhea, headache, and dizziness. These side effects are usually mild and go away on their own after a few days.

However, if the side effects are severe or do not go away, it is important to talk to a doctor. Healthline [3] notes that some of the more serious side effects of acyclovir can include hives, difficulty breathing, and swelling of the face, lips, tongue, or throat. These symptoms could indicate an allergic reaction and require immediate medical attention.

In general, the duration of acyclovir side effects can vary depending on the individual and the severity of the side effects. According to DrugPatentWatch [1], the half-life of acyclovir is approximately 2.5 to 3.3 hours in adults with normal kidney function. This means that the medication is eliminated from the body relatively quickly.

However, some people may experience lingering side effects even after the medication has been eliminated from their system. Healthline [3] notes that some people may experience fatigue, muscle weakness, or confusion while taking acyclovir. These side effects may persist for a few days after the medication is stopped.

In summary, the duration of acyclovir side effects can vary depending on the individual and the severity of the side effects. While most side effects are mild and go away on their own after a few days, it is important to talk to a doctor if the side effects are severe or do not go away. Some people may experience lingering side effects even after the medication has been eliminated from their system. If you experience any serious side effects, seek immediate medical attention.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/ACYCLOVIR
[2] https://www.drugs.com/sfx/acyclovir-side-effects.html
[3] https://www.healthline.com/health/drugs/acyclovir-oral-tablet