Mechanism of Action

ZIRGAN (ganciclovir) ophthalmic gel 0.15% contains the active ingredient, ganciclovir, which is a guanosine derivative that, upon phosphorylation, inhibits DNA replication by herpes simplex viruses (HSV). Ganciclovir is transformed by viral and cellular thymidine kinases (TK) to ganciclovir triphosphate, which works as an antiviral agent by inhibiting the synthesis of viral DNA in 2 ways: competitive inhibition of viral DNA-polymerase and direct incorporation into viral primer strand DNA, resulting in DNA chain termination and prevention of replication.

Pharmacokinetics

The estimated maximum daily dose of ganciclovir administered as 1 drop, 5 times per day is 0.375 mg. Compared to maintenance doses of systemically administered ganciclovir of 900 mg (oral valganciclovir) and 5 mg/kg (IV ganciclovir), the ophthalmically administered daily dose is approximately 0.04% and 0.1% of the oral dose and IV doses, respectively, thus minimal systemic exposure is expected.

Clinical Studies

In one open-label, randomized, controlled, multicenter clinical trial which enrolled 164 patients with herpetic keratitis, ZIRGAN (ganciclovir ophthalmic gel) was non-inferior to acyclovir ophthalmic ointment, 3% in patients with dendritic ulcers Clinical resolution (healed ulcers) at Day 7 was achieved in 77% (55/71) for ZIRGAN (ganciclovir ophthalmic gel) versus 72% (48/67) for acyclovir 3% (difference 5.8%, 95% CI -9.6%-18.3%).

In three randomized, single-masked, controlled, multicenter clinical trials which enrolled 213 total patients, ZIRGAN (ganciclovir ophthalmic gel) was non-inferior to acyclovir ophthalmic ointment 3% in patients with dendritic ulcers. Clinical resolution at Day 7 was achieved in 72% (41/57) for ZIRGAN (ganciclovir ophthalmic gel) versus 69% (34/49) for acyclovir (difference 2.5%, 95%CI-15.6%-20.9%).

Last reviewed on RxList: 9/30/2009
This monograph has been modified to include the generic and brand name in many instances.