OXSORALEN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for OXSORALEN (OXSORALEN).
Psoralen intercalates into DNA and upon UVA exposure forms covalent crosslinks between pyrimidine bases, inhibiting DNA synthesis and cell proliferation.
| Metabolism | Hepatic metabolism via cytochrome P450 enzymes (primarily CYP1A2 and CYP2A6) to inactive metabolites. |
| Excretion | Primarily hepatic metabolism; less than 5% excreted unchanged in urine. Biliary/fecal elimination accounts for the majority of metabolites, though exact percentage not well defined. |
| Half-life | Approximately 2-5 hours for parent drug; clinical effect persists longer due to epidermal DNA binding. |
| Protein binding | >90% bound, primarily to albumin. |
| Volume of Distribution | 0.2-0.5 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: approximately 70-80% with food; topical/bath: systemic absorption minimal (<5%). |
| Onset of Action | Oral: 2-5 hours (peak photosensitivity). Topical: 2-6 hours. Bath: 2 hours. |
| Duration of Action | Oral: up to 8-12 hours of photosensitivity; topical: 12-24 hours; bath: 4-6 hours. |
0.6 mg/kg orally once daily, 2 hours before UV-A exposure, or 0.4 mg/kg orally 2 hours before psoralen plus UV-A (PUVA) therapy. For topical use, a 1% lotion is applied 2 hours prior to UV-A exposure.
| Dosage form | LOTION |
| Renal impairment | No specific dose adjustment guidelines available; caution advised in severe renal impairment due to potential accumulation. |
| Liver impairment | No specific dose adjustment guidelines for Child-Pugh classification; use with caution in hepatic impairment and monitor for adverse effects. |
| Pediatric use | Not recommended in children due to lack of safety and efficacy data; avoid use. |
| Geriatric use | No specific dose adjustment; initiate at lower end of dosing range and monitor closely for adverse effects such as phototoxicity and skin aging. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for OXSORALEN (OXSORALEN).
| Breastfeeding | It is unknown if methoxsalen is excreted in human breast milk. The M/P ratio has not been determined. Because of the potential for serious adverse reactions in nursing infants, including photosensitivity and potential carcinogenicity, breastfeeding is not recommended during treatment with oxsoralen and for a period after the last dose. |
| Teratogenic Risk | Oxsoralen (methoxsalen) is contraindicated in pregnancy. In animal studies, methoxsalen has been shown to be teratogenic and embryotoxic. There are no adequate and well-controlled studies in pregnant women. Based on animal data and its mechanism of action, there is a potential risk for fetal harm if used during pregnancy. Specifically, in the first trimester, there is risk of major malformations. In the second and third trimesters, there is risk of fetal toxicity and growth impairment. Due to these risks, use is not recommended at any stage of pregnancy. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to psoralen compounds","Pregnancy","Lactation","History of melanoma or invasive squamous cell carcinoma","Severe hepatic or renal impairment","Photosensitive disorders (e.g., porphyria, lupus erythematosus)"]
| Precautions | ["Carcinogenic risk (skin cancer) with prolonged use","Severe burns and blistering if UVA exposure is excessive","Photosensitivity reaction lasting up to 8 hours","Ocular toxicity (cataracts) requires eye protection","Hepatotoxicity risk","Not for use in patients with xeroderma pigmentosum or lupus erythematosus"] |
Loading safety data…
| Fetal Monitoring | Monitor for signs of photosensitivity and skin reactions. Perform regular complete blood counts and liver function tests. Ophthalmic examinations are recommended due to risk of cataracts. In pregnancy, if exposure occurs, fetal ultrasonography and assessment for growth and development should be considered. |
| Fertility Effects | Methoxsalen has been associated with reduced fertility in animal studies. In humans, there is limited data, but potential effects on spermatogenesis and ovarian function are possible. Patients of reproductive age should be counseled on the potential impact on fertility. |