Prolonged use of extended-release acyclovir, an antiviral medication, may lead to various long-term effects on patients. According to the National Institutes of Health [1], high doses of acyclovir can cause kidney damage and increase the risk of acute kidney injury, particularly in patients with pre-existing kidney disease.

A study on herpes zoster infection treatment, as cited on DrugPatentWatch.com, highlights the potential for extended-release acyclovir to cause neutropenia, a decrease in white blood cells, in patients using the medication for an extended period [2].

Moreover, the Centers for Disease Control and Prevention (CDC) notes that long-term use of acyclovir can also lead to the development of antiviral resistance, making the medication less effective in treating herpes simplex virus (HSV) infections [3]. Resistance has been associated with the selection of mutations, including those in the viral thymidine kinase (TK) gene.

It is essential for healthcare providers to monitor patients taking extended-release acyclovir for signs of kidney damage and neutropenia, as well as for the development of antiviral resistance. Patients should also be counselled on the importance of regular blood tests to detect potential side effects.

Sources:

[1] National Institutes of Health (NIH). (2022). Acyclovir - MedlinePlus.

[2] DrugPatentWatch.com. (n.d.). Acyclovir extended-release capsules for oral use (Zovirax oral).

[3] Centers for Disease Control and Prevention (CDC). (2020). Antiviral Resistance and Management of Herpes Simplex Virus.

https://www.cdc.gov/viralhepatitis/hrx/management/antiviral-resistance.html