Methoxsalen
Mechanism :
It is a melanising agent used to promote repigmentation in vitiliginous areas of the skin. It is applied topically as it can cause severe adverse effects after oral administration.
Indication :
- Psoralen agent used to enhance ultra violet light therapy of psoriasis.
Contraindications :
Hypersensitivity, anticoagulant therapy, actinic damage, skin cancer, hepatic insufficiency, porphyrias, acute lupus erythematosus, polymorphic light eruptions or other risk factors for skin cancer such as immunosuppression.
Avoid sunbathing, oversensitivity may lead to blistering/burning.
Dosing :
<12 years old: Safety and efficacy not established.
Give orally with milk or food 2 hours before UVA exposure.
<30 kg: 10 mg
30-50 kg: 20 mg
51-65 kg: 30 mg
66-80 kg: 40 mg
81-90 kg: 50 mg
91-115 kg: 60 mg
>115 kg: 70 mg.
Adverse Effect :
Nausea and pruritus are common. Other effects include nervousness, insomnia, erythema, skin, pain and headache.
Interaction :
Concurrent use of fosphenytoin and phenytoin may make treatment ineffective.
Hepatic Dose :
Dose adjustment in hepatic impairment: Specific guidelines are not available. Use with caution as methoxsalen undergoes significant hepatic metabolism.