Topical antiherpetic agents are used for the external treatment of infections caused by herpesviruses. This pharmacological group includes medications for treating lesions of the eyes, skin, and mucous membranes.
IndicationsKeratitis, conjunctivitis, herpes of the skin and mucous membranes
FormulationsEye drops and topical gel
MechanismIdoxuridine and trifluridine are thymidine analogues
SafetyNot used systemically due to high toxicity
Idoxuridine and Its Characteristics
Idoxuridine is a synthetic thymidine analogue. The drug is available as eye drops (known under trade names such as Oftan Idu and Kerecid).
Key characteristics:
Indications: Topical treatment of herpetic keratitis and conjunctivitis.
Regimen: Requires extremely frequent administration — hourly during the day and every two hours at night.
Limitations: Contraindicated for systemic (resorptive) use due to marked toxicity.
Adverse Effects: Contact dermatitis of the eyelids, allergic manifestations, and corneal opacity may occur.
Trifluridine
This drug is also a thymidine analogue and is intended for the same therapeutic objectives as idoxuridine.
Trifluridine has regulatory status variations depending on the regional pharmacopoeia, functioning primarily as an ophthalmic antiviral agent.
Tromantadine for Skin and Mucous Membranes
Tromantadine is formulated as a gel.
Key properties:
Indications: Treatment of herpetic eruptions on the skin and mucous membranes, including manifestations caused by herpes simplex virus (HSV) and herpes zoster (shingles).
Pharmacokinetics: Upon topical application, it practically does not penetrate into the systemic circulation.
Adverse Effects: Limited exclusively to local allergic reactions such as pruritus, erythema, edema, and pain at the application site.
Mnemonic
Instill idoxuridine every hour by day and every two hours at night, and apply tromantadine as a gel without systemic absorption.
Frequently asked questions
What is the mechanism of action of idoxuridine at the molecular level?
Idoxuridine acts as a synthetic thymidine analogue belonging to the group of abnormal nucleosides. At the molecular level, its mechanism of action involves the disruption of viral nucleic acid synthesis. Due to its high toxicity, the drug is not used systemically (resorptively), but is utilized exclusively for the topical treatment of herpetic infections.
Which drugs belong to the group of topical antiherpetic agents?
The group of topical antiherpetic agents includes medications available in formulations for external use.
Idoxuridine — eye drops indicated for the topical treatment of keratitis and conjunctivitis.
Trifluridine — a thymidine analogue for topical use.
Tromantadine — a gel for treating skin and mucosal lesions.
Penciclovir — applied topically for recurrent herpes simplex.
Acyclovir — used as a 5% ointment as a drug of choice.
Which antiherpetic drugs are used to treat herpetic keratitis?
Specific antiviral agents and enzyme preparations are used to treat herpetic keratitis.
Idoxuridine — eye drops indicated for the topical treatment of keratitis and conjunctivitis of herpetic etiology.
Trifluridine — an abnormal nucleoside used in ophthalmology (keratitis of herpetic and adenoviral etiology).
Nucleases (ribonuclease, deoxyribonuclease) — enzymes used as antiviral agents in herpetic keratitis.
Acyclovir and Valacyclovir — prescribed systemically for the ocular form of shingles involving corneal damage (keratitis).
Why cannot idoxuridine be administered orally or via injections?
The drug exhibits high systemic toxicity, which is why it is used exclusively topically.
What is the chemical structure of idoxuridine and trifluridine?
Both drug substances are synthetic analogues of thymidine.
What is the formulation of tromantadine and does it absorb into the blood?
The drug is formulated as a gel and, upon application, practically does not penetrate into the systemic circulation.
Go deeper
Chemical structure of thymidine analogues
Comparison of ophthalmic antiherpetic formulations
Pharmacokinetic features of topical agents
Toxicological profile of idoxuridine
Spectrum of activity of tromantadine in herpes zoster