PHOTREXA VISCOUS IN DEXTRAN 20%/PHOTREXA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PHOTREXA VISCOUS IN DEXTRAN 20%/PHOTREXA (PHOTREXA VISCOUS IN DEXTRAN 20%/PHOTREXA).
Photosensitizing agent that is activated by ultraviolet A (UVA) light; causes cross-linking of DNA in rapidly dividing cells, leading to cell death.
| Metabolism | Hepatic; primarily metabolized by CYP1A2 and CYP2C9 |
| Excretion | Primarily excreted via the reticuloendothelial system into the biliary tract and eliminated in feces; less than 1% excreted renally as unchanged drug. |
| Half-life | Terminal elimination half-life is approximately 12 hours, supporting once-daily dosing for photosensitization. |
| Protein binding | Highly protein-bound (>99%), primarily to albumin and other plasma proteins. |
| Volume of Distribution | Volume of distribution (Vd) is approximately 0.8 L/kg, indicating distribution into extracellular fluid and some tissue binding. |
| Bioavailability | Intravenous: 100% (administered only intravenously). |
| Onset of Action | Intravenous: Onset of photosensitization occurs within 10-15 minutes after completion of infusion (15-minute infusion). |
| Duration of Action | Duration of photosensitization persists for approximately 48 hours, after which patients should avoid direct sunlight for at least 48 hours post-infusion. |
Not applicable. Photrexa Viscous (riboflavin 5'-phosphate in 20% dextran) is used as a photosensitizer during corneal collagen cross-linking (CXL) for keratoconus. The corneal epithelium is removed, and the solution is applied topically to the cornea every 2 minutes for 30 minutes, followed by UV-A irradiation (365 nm, 3 mW/cm²) for 30 minutes.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No adjustment necessary. Ophthalmic use results in negligible systemic absorption. |
| Liver impairment | No adjustment necessary. Ophthalmic use results in negligible systemic absorption. |
| Pediatric use | Same dosing protocol as adults: topical application to de-epithelialized cornea every 2 minutes for 30 minutes prior to UV-A exposure. Limited to patients with progressive keratoconus, typically aged 14 years and older. |
| Geriatric use | No specific adjustment. Use standard adult dosing protocol as in younger adults, considering age-related corneal changes and slower healing. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PHOTREXA VISCOUS IN DEXTRAN 20%/PHOTREXA (PHOTREXA VISCOUS IN DEXTRAN 20%/PHOTREXA).
| Breastfeeding | Methoxsalen is excreted into human breast milk. The milk-to-plasma ratio (M/P) is approximately 0.9. Due to the potential for genotoxic effects in a nursing infant, breastfeeding is not recommended during treatment and should be avoided for at least 24 hours after the last dose. |
| Teratogenic Risk | PHOTREXA VISCOUS IN DEXTRAN 20%/PHOTREXA is a photochemotherapeutic agent containing methoxsalen and dextran. Methoxsalen is a furocoumarin that intercalates with DNA upon UVA activation, forming crosslinks and inhibiting DNA replication. In pregnancy, there is a potential risk of genotoxicity and teratogenicity based on its mechanism of action. Animal studies have shown embryotoxicity and teratogenicity at doses comparable to human exposure. In the first trimester, exposure may increase the risk of congenital malformations; in the second and third trimesters, it may impair fetal growth and development. Use is contraindicated during pregnancy unless no alternative. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to psoralen compounds","Aphakia","History of melanoma or invasive squamous cell carcinoma","Severe hepatic or renal impairment","Pregnancy (Category C)"]
| Precautions | ["Carcinogenicity risk (skin cancer)","Ocular toxicity (cataracts, retinal damage requiring UVA-protective eyewear)","Photosensitivity reactions","Hepatotoxicity"] |
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| Fetal Monitoring | Maternal: Obtain baseline liver function, renal function, and ophthalmologic exam. Monitor for cutaneous phototoxicity, gastrointestinal symptoms, and ocular effects. Fetal: Ultrasound monitoring for growth and anatomy if inadvertent exposure occurs; consider fetal echocardiography if exposure in first trimester. |
| Fertility Effects | Methoxsalen plus UVA (PUVA) therapy has been associated with impaired spermatogenesis in males and may cause ovarian dysfunction in females. In males, decreased sperm count and motility have been reported. In females, temporary or permanent amenorrhea may occur. These effects are dose- and duration-dependent. |