Antiviral agents for herpes

Mechanism of action and main groups

The mechanism of action of antiherpetic agents is based on blocking target enzymes necessary for viral replication. The main group is viral DNA polymerase inhibitors. A typical representative is acyclovir, which is a guanosine analogue and incorporates directly into the viral DNA, terminating its synthesis. Foscarnet also inhibits this enzyme and is used in case of resistance.

Main drug groups:

• Nucleoside analogues: acyclovir, vidarabine, idoxuridine (used for herpes simplex and herpes zoster).
• Broad-spectrum nucleoside analogues: ganciclovir (active against cytomegalovirus).
• Ophthalmological agents: trifluridine (treatment of herpetic keratitis).
• Reserve agents: valacyclovir, famciclovir, foscarnet sodium (prescribed for severe forms or resistance to baseline therapy).

Treatment of localized forms and stomatitis

In mild cases, a combined approach is considered optimal: a combination of topical formulations and systemic administration. The baseline course lasts 7–10 days.

• Acyclovir: 400 mg 3 times daily.
• Valacyclovir: 1 g 2 times daily.
• Famciclovir: 250 mg 4 times daily.

For episodic therapy of recurrent herpes simplex, the course is shortened to 5 days (e.g., acyclovir is prescribed at 200 mg 5 times daily).

For herpetic stomatitis, topical antivirals are applied to the erosions. It is important to remember: topical glucocorticoids are strictly contraindicated when a viral infection is suspected without etiotropic support, as this threatens generalization of the process. Corticosteroids are justified only for aphthous stomatitis (stomatitis aphthosa).

Treatment of severe and generalized infections

Clinical deterioration, involvement of internal organs, or the development of encephalitis require switching to intravenous administration of the baseline drug or using high doses of oral prodrugs.

1. Generalized forms: intravenous acyclovir is the first-line drug (10 mg/kg once daily), the course can be extended up to 14–21 days. If clinical resistance is suspected, foscarnet is used (strictly for 14 days).
2. Herpetic encephalitis: without treatment, mortality exceeds 70%. Administration of acyclovir (from 10 mg/kg every 8 hours) reduces mortality in adult patients by 20–30%. Empirical therapy is started immediately, prior to laboratory confirmation of the diagnosis.
3. Special situations: direct-acting antivirals (acyclovir, ganciclovir) are used in newborns. Specific therapy is vital in Kaposi's varicelliform eruption.

Suppressive therapy and comprehensive approach

Patients with frequently recurring herpes are indicated for suppressive (prophylactic) therapy. Its goal is the continuous suppression of viral reactivation. Drugs are taken orally long-term (e.g., valacyclovir 500 mg once daily). This also reduces the risk of transmitting the infection to a seronegative partner.

A comprehensive approach is used for genital herpes:

• Specific antiviral therapy.
• Interferon system correction: use of inducers (cycloferon, tilorone) or replacement therapy (viferon, reaferon).
• Immunotherapy: specific (herpetic vaccine) and nonspecific (timalin, inosine pranobex).
• Local treatment: antiseptics to prevent secondary purulent infection.

Class and exam questions

What else to study on this topic

• Features of empirical therapy for herpetic encephalitis
• Suppressive therapy regimens to prevent viral transmission
• Use of antiviral agents in newborns and children
• Comprehensive treatment of genital herpes: the role of interferons
• Kaposi's varicelliform eruption: specifics of acyclovir administration

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.