PUVA and other phototherapy

shevyatiwari's version from 2015-04-26 03:13

Section 1

Question Answer
Psoralens are highly hydrophilicF. Lipophilic
Psoralens are ionised compoundsF. Non ionised
8MOP is two times more water soluble than 5MOPF. 3 times
The smaller the particles of psoralen the better the absorptionT
Food esp fatty food does not affect Psoralen F. Delays absorption and peak levels
Psoralens are hydrolysedF. Metabolised in the liver
There is no first pass hepatic metabolismF. Extensive. Doses < 20mg are not effective
First pass metabolism of psoralen is highly saturableT
There are interindividiual and intraindividual variations in BA of psoralensT
8-MOP is more protein bound than 5-MOPF. 8-MOP 75-80, 5-MOP 98-99
8-MOP and 5-MOP are both approx 75-80% protein bound (PP)F. 5-MOP is 98-99% bound
Epidermal tissue binding is the same as PP binding for psoralensF. Different in 8-MOP
Epidermal tissue binding is 75-80% for 8-MOPF. 90%
Epidermal tissue binding is 99% for 5-MOPt
Bioavailability is best measured by the minimal phototoxic doseT
8-MOP is more photoactive than 5-MOPT.
8-MOP undergoes rapid and complete metabolism in the liverT
Metabolites are not activeT
Excretion is predominantly renalT. 74%
Peak absorption occurs in the UVA spectrum 320-400F. 320-330
Type 1 reactions -> prouction of ROS and free radicals leading to damage of cell membranes F
Type 2 reactions consist of photo addition of the compound to pyridines in DNAF. Type 1
PUVA causes suppression of DNA synthesisT
PUVA causes selective immunosuppressionT
PUVA -> selective cytotoxicityT
PUVA stimulates melanocytesT
PUVA is FDA approved for only psoriasisF. Also approved for vitiligo
Pemphigus, pemphigoid, lupus, xeroderma pigmentosum, lactation, and reactions to psoralen are relative C/IF. Absolute
Photosensitivity is an absolute C/IF. Relative
Prior exposure to radiation, personal/family history of melanoma, skin cancer, pregnancy, cardiac, liver, renal disease and young age are absolute C/IF. Relative
The blistering phototoxic reactions of topical psoralen is likely due to sun exposure after therapT
Psoralen are secreted in breast milkT
The use of a photosensitising medication should warrant dose adjustment of UVAT. Approx 25%. Only for potent sensitisers like doxycycline or fluoroquinolone Not thiazide diuretics
Doxycycline and fluroquinolones (esp sparfloxacin and lomefloxacin) are drug interactions with psoralenT
Aphakia (absence of the lens) is not a C/I provided there is good protectionT
8-MOP is taken the night before PUVAF. Taken 1-2 hours prior
0.4mg/kg has better and more predictable absorption than the 0.6mg/kg formulationT. Lower dose, less nausea, cheaper, better absorption, can be exposed within 1 hour
Food should be avoided until after treatmentT
Measuring the MPD and starting therapy at 70% of this dose -> less cumulative UVAT
If widespread erythema is present prior to a treatment, dose should be stopped until it clearsT
>5% return of psoriasis warrants increase frequency of treatmentsT
Topical CS may be required for areas naturally shielded from UVA as an adjunctT
NBUVB is as effective as PUVA in activating psoralenT.
Mtx, acitretin, BBUVB, calcioptriene, tazarotene are all relative C/I with 8-MOPF. Can be used as concurrent therapy
Nausea is proportional to drug level T
The most common side effect of PUVA is symptomatic erythemaT. Give supportive treatments
Pruritis and subacute phototoxicity are indications to stop treatmentT, restart when resolved at a lower dose
Headache and CNS issues including depression, hyperactivity and insomnia can be due to PUVAT.
Bronchoconstriction can occur with psoralenT
Fevers and exanthema can occur with psoralensT
Melanoma and NMSC can occur as long term effectsT
Cataracts, and immunosuppression can be long term effectsF. No evidence
CYP inducers such as carbamazepine, and phenytoin can reduce the effectiveness of treatmentT
Topical PUVA is diluted with ethanol or in bathwaterT
Drug levels can be detected with topical psoroalenT
While in PUVA, goggles should be wornT
Wrap around UV opaque glasses should be worn until sunsetT
Eye protection is necessary for topical PUVAT

Section 2

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