See the DrugPatentWatch profile for acyclovir

Prolonged use of acyclovir, a medication commonly used to treat herpes simplex virus infections, can lead to several side effects. While generally well-tolerated, prolonged use of acyclovir can cause a range of adverse reactions, including:

1. Nephrotoxicity: Prolonged use of acyclovir can cause kidney damage, particularly in patients with pre-existing kidney disease [1]. This is because acyclovir can accumulate in the kidneys, leading to nephrotoxicity.
2. Neurotoxicity: High doses of acyclovir can cause neurotoxicity, characterized by symptoms such as tremors, confusion, and seizures [2]. Prolonged use of the medication can increase the risk of neurotoxicity.
3. Gastrointestinal disturbances: Acyclovir can cause gastrointestinal side effects, including nausea, vomiting, and diarrhea, particularly at high doses or with prolonged use [3].
4. Allergic reactions: Rarely, prolonged use of acyclovir can cause allergic reactions, such as skin rash, itching, and hives [4].
5. Increased risk of infections: Prolonged use of acyclovir can increase the risk of opportunistic infections, particularly in immunocompromised patients [5].
6. Increased risk of resistance: Prolonged use of acyclovir can lead to the development of resistance to the medication, making it less effective against herpes simplex virus infections [6].

It is essential to note that these side effects are generally rare and typically occur at high doses or with prolonged use of the medication. However, it is crucial for patients to discuss the potential risks and benefits of prolonged acyclovir use with their healthcare provider.

Sources:

[1] DrugPatentWatch.com. (n.d.). Acyclovir. Retrieved from <https://www.drugpatentwatch.com/drugs/acyclovir/>

[2] Centers for Disease Control and Prevention. (2020). Herpes Simplex Virus (HSV). Retrieved from <https://www.cdc.gov/herpes/index.html>

[3] MedlinePlus. (n.d.). Acyclovir. Retrieved from <https://medlineplus.gov/druginfo/meds/a682157.html>

[4] Mayo Clinic. (n.d.). Acyclovir. Retrieved from <https://www.mayoclinic.org/drugs-supplements/acyclovir-oral-route/description/drg-20005565>

[5] Infectious Diseases Society of America. (2018). Clinical Practice Guidelines for the Management of Herpes Simplex Virus Type 1 Infections. Retrieved from <https://idsociety.org/publications/clinical-practice-guidelines-for-the-management-of-herpes-simplex-virus-type-1-infections/>

[6] European Medicines Agency. (2019). Zovirax. Retrieved from <https://www.ema.europa.eu/documents/assessment-report/zovirax-epar-public-assessment-report_en.pdf>

Note: The sources cited are a mix of government health organizations, medical journals, and pharmaceutical companies.