VITRASERT
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VITRASERT (VITRASERT).
Vitrasert (ganciclovir implant) releases ganciclovir, a nucleoside analog that inhibits cytomegalovirus (CMV) replication by competitively inhibiting viral DNA polymerase (UL54) after intracellular phosphorylation to ganciclovir triphosphate. This results in chain termination and viral DNA synthesis inhibition.
| Metabolism | Ganciclovir is primarily eliminated unchanged by the kidney via glomerular filtration and tubular secretion. Hepatic metabolism is minimal; no specific cytochrome P450 enzymes are involved. |
| Excretion | Primarily biliary/fecal (approximately 90%) with minimal renal excretion (<10% unchanged in urine). |
| Half-life | Terminal half-life of 2.8 hours following intravitreal injection; sustained local levels for 2-3 weeks. |
| Protein binding | Extensive (99% bound) primarily to albumin. |
| Volume of Distribution | Systemic Vd not clinically relevant; local ocular distribution ~4 mL (vitreous volume). |
| Bioavailability | Intravitreal: 100% (local). |
| Onset of Action | Intravitreal: within 2 weeks of injection. |
| Duration of Action | Intravitreal: approximately 3-4 months (single implant); effect may last up to 8 months. |
Intravitreal implant containing 0.59 mg fluocinolone acetonide; inserted into the vitreous cavity; releases drug over approximately 36 months; no systemic dosing.
| Dosage form | IMPLANT |
| Renal impairment | No dose adjustment required; renal impairment does not affect intravitreal pharmacokinetics. |
| Liver impairment | No dose adjustment required; hepatic impairment does not affect intravitreal pharmacokinetics. |
| Pediatric use | Not indicated for pediatric patients; safety and efficacy not established. |
| Geriatric use | No specific dose adjustment; same as adult dosing; monitor for intraocular pressure elevation and cataract progression. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for VITRASERT (VITRASERT).
| Breastfeeding | It is unknown if ganciclovir is excreted in human milk. The M/P ratio has not been determined. Because of the potential for serious adverse reactions in nursing infants, breastfeeding is not recommended during therapy. |
| Teratogenic Risk | Vitrasert (ganciclovir implant) is classified as Category C. First trimester: There is no adequate human data, but animal studies show embryotoxicity and teratogenicity (e.g., cleft palate, anophthalmia). Second and third trimesters: Potential for fetal toxicity based on animal data, but limited human experience. Use only if benefit outweighs risk. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to ganciclovir or acyclovir","Neutrophil count less than 500 cells/μL","Platelet count less than 25,000 cells/μL"]
| Precautions | ["Severe leukopenia, neutropenia, anemia, thrombocytopenia","Potential for retinal detachment","Risk of endophthalmitis and vitreous hemorrhage with implantation procedure","Impaired renal function may require dose adjustment of systemic ganciclovir","Carcinogenicity, mutagenicity, and impairment of fertility observed in animal studies"] |
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| Fetal Monitoring | Monitor maternal complete blood count (neutropenia, thrombocytopenia), liver function tests, and serum creatinine. Fetal monitoring: Consider serial ultrasound for fetal growth and anatomy due to potential embryotoxicity. |
| Fertility Effects | Animal studies have shown decreased fertility in male and female rats at high doses. In humans, no specific data; however, ganciclovir may impair spermatogenesis and cause ovarian failure based on preclinical findings. |