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Photochemotherapy
Published in Henry W. Lim, Nicholas A. Soter, Clinical Photomedicine, 2018
Two approaches to treatment are commonly used. Indoor therapy: Oral methoxsalen and exposure to UVA radiation in an office or clinic give the best results. A three times per week or twice per week schedule is used with the aim of producing and maintaining a faint pink color in the areas of vitiligo. Topical application of methoxsalen as a solution is used in some centers and good results have been reported. This technique is associated with a high frequency of unexpected blistering erythemas, which can Koebnerize to produce more vitiligo.Outdoor therapy: Trioxsalen and exposure to sunlight achieve reasonable results in a sunny climate. Trioxsalen is taken orally in a dosage of 0.6 mg/kg body weight and exposure to sunlight is commenced 2 hr later, starting with 5 min and increasing gradually up to 1 hr on each side. The exposure should ideally be done in the middle of the day and of course the treatment is restricted to the summer months in colder climates.
Systemic and Topical PUVA Therapy
Published in John Y. M. Koo, Ethan C. Levin, Argentina Leon, Jashin J. Wu, Alice B. Gottlieb, Moderate to Severe Psoriasis, 2014
Warwick L. Morison, Elisabeth G. Richard
Direct application of psoralen to the skin, combined with subsequent exposure to UVA radiation, has been used for the treatment of psoriasis for almost as long as oral PUVA therapy. The first approach used a dilute solution of trimethylpsoralen (TMP) in a bath [32,33], and subsequent studies have used methoxsalen and 5-methoxypsoralen in bath solutions as well as creams and lotions. Topical PUVA therapy is used most widely used in Europe and it appears. And it appears to be much less popular elsewhere. In addition, because methoxsalen is the only psoralen available for use in the United States, this section will only discuss treatment with this agent. The suggested advantages of topical PUVA therapy are Marked reduction of systemic exposure to methoxsalen so that gastrointestinal side effects and risk of cataracts are virtually eliminated.Possible improved efficacy.Possible reduced risk of skin cancer.
Psoralen Photochemotherapy
Published in Henry W. Lim, Herbert Hönigsmann, John L. M. Hawk, Photodermatology, 2007
Warwick L. Morison, Herbert Hönigsmann
Soak PUVA therapy uses a basin containing about 5 L of water and is useful for treating hand and foot diseases. Methoxsalen in a cream or gel has been used for local treatments and the kinetics of photosensitivity are similar to bath PUVA.
Methoxsalen as an in vitro phenotyping tool in comparison with 1-aminobenzotriazole
Published in Xenobiotica, 2019
Raghava Choudary Palacharla, Parusharamulu Molgara, Hanumanth Rao Panthangi, Rajesh Kumar Boggavarapu, Arun Kumar Manoharan, Ranjith Kumar Ponnamaneni, Devender Reddy Ajjala, Ramakrishna Nirogi
Methoxsalen (also known as 8-MOP, psoralen) is a naturally occurring constituent found in the seeds of Ammi majus plant belonging to the family, Umbelliferae. Methoxsalen belongs to a group of chemical constituents known as furocoumarins. Methoxsalen is used for treating psoriasis, idiopathic vitiligo and cutaneous T-cell lymphoma. Methoxsalen acts as a photosensitizer and the skin reactivity to ultraviolet radiation is markedly enhanced in the presence of methoxsalen. It is a potent inhibitor of CYP2A6 in vitro and is used as a positive control inhibitor in the coumarin hydroxylation activity assay. Methoxsalen is also a potent metabolism-dependent inhibitor of CYP2A6 (Draper et al., 1997). Besides being a potent CYP2A6 inhibitor methoxsalen is an inhibitor of other cytochrome P450 (P450) enzymes (Nirogi et al., 2015; Zhang et al., 2001). 1-aminobenzotriazole (ABT) is being used as a nonspecific inactivator of P450 enzymes in the in vitro reaction phenotyping studies at a concentration of 1 mM in pre-incubation mode to distinguish the P450 mediated metabolism from non-P450 mediated metabolism. It is known that ABT can’t inhibit certain P450 enzyme activities, such as diclofenac hydroxylation mediated by CYP2C9 (Linder et al., 2009). There is a need for more suitable nonspecific inactivator that can distinguish the P450 mediated metabolism from non-P450 mediated metabolism to be used in phenotyping studies with human liver microsomes (HLM).
Sunlight radiation as a villain and hero: 60 years of illuminating research
Published in International Journal of Radiation Biology, 2019
Julia Montelin Powers, James Edward John Murphy
The parent molecule in the furanocoumarin family is psoralen (Briggs, & Colebrook 1960); as with the other members of the family, the multiple double bonds making up its ring structures are strongly absorptive in the ultraviolet B range of 290–310 nm (Steck and Bailey 1969), potentially increasing its phototoxicity. Between 1958 and 1960, dermatological experiments were carried out using it and another member of the furanocoumarin family, methoxsalen. A trial to determine its efficacy in curing vitiligo when taken orally or applied to the skin produced a variety of results, from limited success to outbreaks of severe itching in sunlight (Elliott 1959). Further experimentation using oral methoxsalen to increase tanning in 25 persons with fair skin who had always burned in the past found that it increased tolerance of sunlight, while one developed a basal cell carcinoma after two weeks at a high altitude, and two children, aged four and five, had to cease therapy due to severe swelling of the lips and feet (Stegmaier 1959). It was later added to suntan lotions, particularly in Europe, until it was found to be carcinogenic when combined with sun exposure (Ashwood-Smith et al. 1980; Zajdela and Bisagni 1981; Autier et al. 1997). Methoxsalen is still used on affected areas topically to treat vitiligo (Oxsoralen (Methoxsalen Lotion): Side Effects, Interactions, Warning, Dosage and Uses,https://www.rxlist.com/oxsoralen-drug.htm#side_effects) and prescribed orally for psoriasis, both in combination with physician-administered UVA treatment (Methoxsalen Oral: Uses, Side Effects, Interactions, Pictures, Warnings and Dosing – WebMD; https://www.webmd.com/drugs/2/drug-6957-1257/methoxsalen-oral/methoxsalen-rapid-oral/details).
The 2-year rodent bioassay in drug and chemical carcinogenesis testing: Sensitivity, according to the framework of carcinogenic action
Published in Toxicology Mechanisms and Methods, 2020
Jose D. Suarez-Torres, Fausto A. Jimenez-Orozco, Carlos E. Ciangherotti
The rationale was: merphalan is a racemic mixture of melphalan and medphalan (13045-94-8) (IARC 1975). In rats, the carcinogenicity of tobacco smoke was recognized from exposure to mainstream tobacco smoke. In mice, the carcinogenicity of tobacco smoke was recognized from exposure to a mixture of sidestream and exhaled-mainstream tobacco smoke. Methoxsalen plus ultraviolet A radiation, as a human carcinogen (IARC 2012), was included because there is evidence that methoxsalen (298-81-7) plays an essential role in the carcinogenicity of this composite physicochemical agent (Forbes and Urbach 1975a, 1975b; Dunnick et al. 1991).