Brand name: Zirgan
Drug class: Antivirals
Chemical name: 2-Amino-1,9-dihydro-9-[2-hydroxy-1-(hydroxymethyl)ethoxy]methyl]-6H-purin-6-one
Molecular formula: C₉H₁₃N₅O₄
CAS number: 82410-32-0

Introduction

Antiviral; purine nucleoside analog of guanine.

Uses for Ganciclovir

Herpetic Keratitis

Topical treatment of acute herpetic keratitis in patients with dendritic ulcers; designated an orphan drug by FDA for treatment of acute herpetic keratitis (dendritic and geographic^{† [off-label]} ulcers).

Herpetic keratitis usually caused by herpes simplex virus (HSV) type 1 (HSV-1), but can be caused by HSV type 2 (HSV-2).

Ganciclovir Dosage and Administration

Administration

Ophthalmic Administration

Apply 0.15% ophthalmic gel topically to the eye.

To avoid contaminating the ophthalmic gel, do not allow tip of dispensing dropper to touch any surface.

Dosage

Pediatric Patients

Herpetic Keratitis

Ophthalmic

Children ≥2 years of age with dendritic ulcers: Instill 1 drop of 0.15% ophthalmic gel into affected eye 5 times daily (approximately every 3 hours while awake) until corneal ulcer heals. Then, instill 1 drop 3 times daily for 7 additional days.

Children ≥2 years of age with geographic ulcers^{† [off-label]}: Some experts state use same dosage recommended for dendritic ulcers.

Adults

Herpetic Keratitis

Ophthalmic

Dendritic ulcers: Instill 1 drop of 0.15% ophthalmic gel into affected eye 5 times daily (approximately every 3 hours while awake) until corneal ulcer heals. Then, instill 1 drop 3 times daily for 7 additional days.

Geographic ulcers^{† [off-label]}: Some experts state use same dosage recommended for dendritic ulcers.

Special Populations

No special population dosage recommendations.

Cautions for Ganciclovir

Contraindications

• Manufacturer states none.

Warnings/Precautions

Administration Precautions

For topical ophthalmic use only.

Do not wear contact lenses during topical treatment with ganciclovir gel or if any signs or symptoms of herpetic keratitis are present.

Specific Populations

Pregnancy

Category C.

Use only if potential benefits to the woman justify risks to the fetus.

No adequate, well-controlled studies in pregnant women; IV ganciclovir associated with embryotoxicity, teratogenicity, and/or maternal toxicity in animal studies.

Lactation

Not known whether distributed into milk after topical application to the eye.

Use with caution in nursing women.

Pediatric Use

Safety and efficacy not established in children <2 years of age.

Geriatric Use

No overall differences in safety or efficacy observed between geriatric and younger patients.

Common Adverse Effects

Blurred vision, eye irritation, punctate keratitis, conjunctival hyperemia.

Ganciclovir Pharmacokinetics

Absorption

Bioavailability

Minimal systemic exposure expected when 0.15% gel administered by topical ophthalmic application.

Distribution

Extent

Following topical ophthalmic application, penetrates corneal stroma (principally by passive diffusion) and therapeutic concentrations are attained in aqueous humor.

Stability

Storage

Ophthalmic

Gel

15–25°C; do not freeze.

Contains benzalkonium chloride as a preservative.

Actions and Spectrum

• Nucleoside analog of guanine; structurally and pharmacologically related to acyclovir.

• Inactive until converted intracellularly to ganciclovir triphosphate. Selectively phosphorylated by viral and cellular thymidine kinases to form the active triphosphate metabolite.

• Ganciclovir triphosphate accumulates in virus-infected host cells; does not accumulate in uninfected cells.

• Interferes with viral DNA synthesis by competitively inhibiting viral DNA polymerase and by direct incorporation into viral primer strand DNA, resulting in DNA chain termination and prevention of viral replication.

• Active in vitro and in vivo against HSV-1 and HSV-2. Also active in vitro against other Herpesviridae, including cytomegalovirus (CMV), Epstein-Barr virus (EBV), and varicella-zoster virus (VZV).

• HSV resistant to ganciclovir reported only rarely. Cross-resistance between acyclovir and ganciclovir can occur. HSV clinical isolates resistant to acyclovir because of mutation affecting viral thymidine kinase generally are cross-resistant to ganciclovir, famciclovir, and valacyclovir.

Advice to Patients

• To avoid contaminating ganciclovir ophthalmic gel, advise patients that tip of the dispensing dropper should not be allowed to touch any surface.

• Importance of contacting a clinician if pain develops or if redness, itching, or inflammation becomes aggravated.

• Advise patients not to wear contact lenses during treatment with ganciclovir ophthalmic gel.

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.

• Importance of informing patients of other important precautionary information.

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

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