methoxsalen: clinical use

Prescribing considerations

• Restrict use to clinicians trained in CTCL management and the compatible photopheresis system.
• Use only ex vivo in the photoactivation bag; never inject directly into the patient.
• Review photosensitising medicines, recent intense sun exposure, skin-cancer history, hepatic or renal impairment and ability to tolerate extracorporeal volume changes.
• Provide clear UVA eye and skin protection instructions and contraception counselling.

Contraindications and cautions

• Hypersensitivity to methoxsalen, another psoralen or an excipient
• Pregnancy or lactation
• Inadequate contraception in sexually active patients of reproductive potential
• Aphakia
• Photosensitive disease such as porphyria, systemic lupus erythematosus or albinism
• Inability to tolerate extracorporeal volume loss
• Marked leukocytosis, previous splenectomy or coagulation disorder

Monitoring

• Assess blood count, hepatic and renal function, vascular access and suitability for extracorporeal treatment.
• Monitor blood pressure, temperature and clinical condition around each procedure.
• Follow skin manifestations and overall disease response over time.
• Check for infection, vascular-access complications, anaemia and prolonged photosensitivity.

Clinical pharmacology

UVA activation converts DNA-intercalated methoxsalen into covalent photoadducts and cross-links, causing proliferative arrest and apoptosis of treated lymphocytes. Extracorporeal administration produces low systemic exposure after reinfusion. Methoxsalen is highly albumin-bound, extensively metabolised and can inhibit several hepatic cytochrome P450 pathways.

Formulation and product differences

• The selected formulation is a clear solution intended solely for modification of a separated blood fraction in the compatible photopheresis system.
• It is not an oral PUVA preparation and must not be injected directly into the patient.
• It contains ethanol and is essentially sodium-free; systemic effects from the small ethanol content are not expected with extracorporeal administration.
• The solution can adsorb to plastics, so only specified system components should be used; it should not be diluted.