Background: Herpes simplex (HSV) viruses are widely spread, highly contagious
human pathogens. The statistics indicate that 50-90% of adults worldwide are seropositive for
these viruses, mainly HSV-1 and HSV-2. The primary infection results in the appearance of
watery blisters (cold sores) on the skin, lips, tongue, buccal mucosa or genitals. The ocular
infection is the major cause of corneal blindness in the Western World. Once the HSV virus
enters human body, it cannot be completely eradicated because HSV viruses are able to
change into their latent form which can survive the treatment. The viron resides in trigeminal
ganglia of the host, who becomes vulnerable to the reoccurrence of the disease during the
whole lifespan. The neurotropic and neuro-invasive properties of HSV are responsible for
neurodegenerative illnesses, such as Alzheimer's disease. Acyclovir and its analogues, being
the inhibitors of the viral DNA replication, are the only approved medicines for HSV infection
Objective: The current paper presents the up-to-date overview of the important pharmacological
features of acyclovir, its analogues and their delivery systems including the mechanism of
action, routes of administration, absorption and metabolism, as well as side effects of the therapy.
Conclusion: Acyclovir remains the gold standard in the treatment of herpes virus infections,
mainly due to the emerging of the new delivery systems improving considerably its bioavailability.
The analogues of acyclovir, especially their esters, characterized by significantly
higher bioavailability and safety, may gradually replace acyclovir in selected applications.