📋 Clinical Overview

Ganciclovir is a synthetic nucleoside analogue of 2'-deoxyguanosine with potent antiviral activity against human cytomegalovirus (CMV) and other herpesviruses. The 1.5mg strength is typically found in intravitreal implants for localized treatment of CMV retinitis, a critical formulation for sight-threatening infection in immunocompromised patients, particularly those with AIDS in the Indian context.

💊 Dosage & Administration

Adult: Intravitreal Implant (1.5mg): One implant surgically inserted into the posterior segment of the eye. It releases approximately 1 µg/hr over 5-8 months. Re-implantation may be performed when the implant is exhausted.

Note: INTRAVITREAL IMPLANT: Must be administered by a qualified ophthalmologist under strict aseptic conditions in an operating room. The implant is surgically placed in the posterior segment via pars plana incision. Topical antibiotics and mydriatics are used pre-and post-op. Patient must be monitored for intraocular pressure, endophthalmitis, and retinal detachment.

⚠️ Contraindications

Hypersensitivity to ganciclovir, valganciclovir, or any component of the formulation.
Absolute neutrophil count <500 cells/µL (for systemic therapy).
Platelet count <25,000/µL (for systemic therapy).
Haemoglobin <8 g/dL (for systemic therapy).

🔬 Mechanism of Action

Ganciclovir is a prodrug that requires triphosphorylation for activation. Viral kinases, primarily the UL97 gene product in CMV, initiate monophosphorylation. Cellular kinases then convert it to ganciclovir triphosphate, which competitively inhibits viral DNA polymerase (UL54 gene product) and incorporates into the viral DNA chain, causing premature chain termination.

🤕 Side Effects

Ocular: Transient hypotony, mild vitreous hemorrhage, post-operative inflammation, increased intraocular pressure.
Systemic (from implant are rare but from systemic therapy): Diarrhea, fever, nausea, vomiting, abdominal pain, headache, insomnia.

🤰 Special Populations

Pregnancy: Pregnancy Category C (US FDA). Teratogenic and embryotoxic in animals at systemic doses. There are no adequate studies in pregnant women. Should be used only if the potential benefit justifies the potential risk to the fetus. For the implant, risk is primarily from possible systemic leakage.

Driving: Patients may experience blurred vision, dizziness, or confusion. Caution advised against driving or operating machinery until visual acuity is stable and they know how the medicine affects them.

🔄 Drug Interactions

Zidovudine (AZT)	Increased risk of severe myelosuppression (additive neutropenia).	Major
Mycophenolate Mofetil	Potential additive immunosuppression and increased risk of CMV infection paradoxically.	Moderate
Imipenem-Cilastatin	Increased risk of seizures.	Major
Probenecid	Decreases renal clearance of ganciclovir, increasing plasma levels and toxicity risk.	Moderate
Other Nephrotoxic drugs (Amphotericin B, Cyclosporine, NSAIDs)	Increased risk of renal impairment, reducing ganciclovir clearance.	Moderate
Didanosine (ddI)	May increase didanosine levels; increased risk of pancreatitis and peripheral neuropathy.	Moderate

Cytevir