See the DrugPatentWatch profile for acyclovir

Acyclovir is a commonly prescribed antiviral medication used to treat and prevent herpes simplex virus (HSV) and varicella-zoster virus (VZV) infections, including cold sores, genital herpes, and shingles [1]. According to the available information, there is no evidence to suggest that acyclovir's effectiveness changes with prolonged usage [2].

Acyclovir works by inhibiting viral DNA replication, thereby preventing the virus from multiplying [1]. The drug has a well-established safety and efficacy profile, and its effectiveness is not diminished with prolonged use [2]. However, it is important to note that acyclovir does not cure HSV or VZV infections; it only helps manage the symptoms and reduce the risk of transmission [1].

It is also worth mentioning that acyclovir resistance can develop in some individuals, particularly those who are immunocompromised or have been exposed to the virus for an extended period [2]. In such cases, alternative antiviral medications may be required [2].

In summary, based on the available information, acyclovir's effectiveness does not change with prolonged usage. However, it is essential to follow the recommended dosage and duration of treatment as prescribed by a healthcare professional [1].

Sources:
[1] Mayo Clinic. (2021). Acyclovir (Oral Route). Retrieved from <https://www.mayoclinic.org/drugs-supplements/acyclovir-oral-route/description/drg-20062739>
[2] DrugPatentWatch.com. (2021). Acyclovir. Retrieved from <https://www.drugpatentwatch.com/drugs/acyclovir>