3 - PUVA, NB-UVB and UVA-1 phototherapy Flashcards
UVA wavelength is 320-400nm
True
UVB wavelength is 311nm
True
Psoralen plus ultraviolet A (PUVA) photochemotherapy is the photochemical interaction between a psoralen medication and UVA radiation
True
Psoralens are naturally occurring compounds acting as natural insecticides
True
Human contact with plants containing psoralens and subsequent exposure to sunlight results in phytophotodermatitis
True
Phytophotodermatitis represents an acute phototoxic reaction in the skin manifested as erythema, blistering and pigmentation
True
The presence of psoralen in the skin before and after exposure can be harmful through unintentional exposure to sunlight resulting in undesirable phototoxicity
True
Psoralens are lipophilic and poorly soluble in water
True
There are 2 types of psoralens available, namely 8-MOP (methoxsalen) and 5-MOP (bergapten) where 8-MOP is more water soluble than 5-MOP
True
The water solubility of psoralens determines the bioavailability of these compounds
True
8-MOP (Methoxsalen) is available as 2 formulations of dissolved psoralen (Oxsoralen Ultra) and micronised crystals of 8-MOP
True
Dissolved psoralen (Oxsoralen Ultra) is rapidly and more completely absorbed as compared to the 8-MOP micronised crystals
True (accounts for dissolved psoralen being dosed at 0.4mg/kg and taken 1 hour prior to UVA and micronised crystals 8-MOP being dosed at 0.6mg/kg and 2 hours prior to UVA)
High fat foods can slow down the absorption of psoralens
True (psoralens is ideally taken under fasting conditions although food intake can be used to alleviate the nausea associated with high serum level of the drug)
Nausea is associated with high serum levels of psoralen
True (food intake with the drug can alleviate this adverse effect)
Psoralens exhibit first pass metabolism in the liver and intestines
True (therefore doses <20mg may not be clinically effective)
Psoralens highly bind to serum albumin
True
8-MOP (Methoxsalen) is more photoactive than 5-MOP (Bergapten)
True
The physical formulation of psoralen influences its absorption
True (8-MOP dissolved psoralen more readily absorbed than 8-MOP micronised crystals)
Methoxsalen (8-MOP) is completely metabolised in the liver through the CYP 450 system
True
Cytochrome P450 inducers have an effect on the metabolism of psoralens
True (cytochrome P450 inducers enhance and accelerate the metabolism of 8-MOP therefore reducing the biological effect of PUVA)
Most of 8-MOP is excreted in the kidneys
True
The peak of the absorption spectrum for psoralen molecules to be activated to the excited singlet state is in the region of 320-330nm
True
PUVA therapy suppresses DNA synthesis through the formation of monoadducts and cross links in the DNA
True
PUVA therapy causes selective immunosuppression
True
NB-UVB phototherapy is almost as effective as PUVA for psoriasis not involving the palms and soles
True
NB-UVB has replaced PUVA as the treatment of choice for vitiligo as both treatments have comparable efficacy but NB-UVB is simpler
True
Vitiligo on the face and torso are more responsive to phototherapy than on the limbs
True
The eczematous and plaque stages of mycosis fungoides respond to PUVA
True
The tumour stage of mycosis fungoides does not usually respond to PUVA
True (PUVA is usually not effective in the tumour phase of the disease)
Sezary syndrome is not responsive to PUVA
True
Patients with various photodermatoses can be desensitised by prophylactic exposure to a brief course of PUVA
True