Oxsoralen

Name: Oxsoralen

Pharmacology

Half-Life: 0.75-2.4 hr

Onset: 1-2 hr

Duration: 3-8 hr

Peak Plasma:

Time: 3 hr (conventional cap); 1.8 hr (liquid-filled cap)

Concentration: liquid-filled cap 2-3 x more than conventional cap

Other Information

Bioavailability: variable; enhanced by food

Protein Bound: 75-91%

Metabolism: hepatic

Metabolites: 8-hydroxypsoralen; glucuronide & sulfate conjugates

Excretion: urine

Mechanism of Action

Photosensitizer; preferentially taken up by epidermal cells and binds to DNA, making it more susceptible to ultraviolet radiation damage

8-methoxypsoralen - photoactive derivative of Ammi majus and Heraclem candicans plants

Descriptions

Methoxsalen belongs to the group of medicines called psoralens. It is used along with ultraviolet light (found in sunlight and some special lamps) in a treatment called psoralen plus ultraviolet light A (PUVA) to treat vitiligo, a disease in which skin color is lost. Methoxsalen may also be used for other conditions as determined by your doctor.

Methoxsalen is available only with a prescription and is to be administered by or under the direct supervision of your doctor.

This product is available in the following dosage forms:

  • Lotion

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Reviewed on 6/24/2016 References REFERENCE: FDA Prescribing Information

How supplied

Oxsoralen Lotion containing 1% methoxsalen (8-methoxypsoralen) packaged in 1 ounce (29.57 ml) amber glass bottles (NDC 0187-0402-31). Store at 25°C (77°F); excursion permitted to 15°C-30°C (59°F-86°F).

Manufactured by: Sun Pharmaceuticals Industries, Inc., Bryan, OH 43506 U.S.A. Manufactured for: Valeant Pharmaceuticals North America LLC, Bridgewater, NJ 08807. Revised: May 2011

Clinical pharmacology

The exact mechanism of action of methoxsalen with the epidermal melanocytes and keratinocytes is not known. Psoralens given orally are preferentially taken up by epidermal cells (Artuc et al, 1979)1. The best known biochemical reaction of methoxsalen is with DNA. Methoxsalen, upon photoactivation, conjugates and forms covalent bonds with DNA which leads to the formation of both monofunctional (addition to a single strand of DNA) and bifunctional adducts (crosslinking of psoralen to both strands of DNA) (Dall'Acqua et al, 1971)2. Reactions with proteins have also been described (Yoshikawa et al, 1979)3.

Methoxsalen acts as a photosensitizer. Topical application of this drug and subsequent exposure to UVA, whether artificial or sunlight, can cause cell injury. If sufficient cell injury occurs in the skin an inflammatory reaction will result. The most obvious manifestation of this reaction is delayed erythema which may not begin for several hours and may not peak for 2 to 3 days or longer. It is crucial to realize that the length of time the skin remains sensitized or when the maximum erythema will occur is quite variable from person to person. The erythematous reaction is followed over several days or weeks by repair which is manifested by increased melanization of the epidermis and thickening of the stratum corneum. The exact mechanics are unknown but it has been suggested that melanocytes in the hair follicles are stimulated to move up the follicle and to repopulate the epidermis. (Ortonne, et al, 1979)4

REFERENCES

1. Artuc, M.; Stuettgen, G.; Schalla, W.; Schaefer, H.; Gazith, J.: Reversible binding of 5- and 8- methoxypsoralen to human serum proteins (albumin) and to epidermis in vitro; Brit. J. Dermat., 101, pp. 669-677 (1979).

2. Dall'Acqua, F.; Marciani, S.; Ciavatta, L.; Rodighiero, G.: formation of interstrand cross-linkings in the photoreactions between furocoumarins and DNA; Z Naturfors ch (B), 26, pp. 561-569 (1971).

3. Yoshikawa, K.; Mori, N.; Sakakibara, S.; Mizuno, N.; Song, P.: Photo-Conjugation of 8- methoxypsoralen with Proteins; Photochem & Photobiol, 29, pp. 1127-1133 (1979).

4. Ortonne, J. P.; MacDonald, D.M.; Micoud, A.; Thivolet, J.: PUVA-induced repigmentation of vitiligo: a histochemical (split-DOPA) and ultra-structural study; Brit. J. Dermat., 101, pp. 1-12 (1979).

Patient information

No information provided. Please refer to the WARNINGS and PRECAUTIONS sections.

Pediatric

Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of methoxsalen in children up to 12 years of age with use in other age groups.

Uses of Oxsoralen

  • It is used to treat white patches on your skin (vitiligo).
  • It is used with light therapy.

Iii. indications and usage

As a topical repigmenting agent in vitiligo in conjunction with controlled doses of ultraviolet A (320-400 nm) or sunlight.

Vi. precautions

A. This product should be applied only in small well-defined lesions and preferably on lesions which can be protected by clothing or a sunscreen from subsequent exposure to radiant UVA. If this product is used to treat vitiligo of face or hands, be very emphatic when instructing patient to keep the treated areas protected from light by use of protective clothing or sunscreening agents. The area of application may be highly photosensitive for several days and may result in severe burn injury if exposed to additional UV or sunlight.

B. CARCINOGENESIS

See Warning Section.

C. Pregnancy Category C

Animal reproduction studies have not been conducted with topical methoxsalen. It is also not known whether methoxsalen can cause fetal harm when used topically on a pregnant woman or affect reproductive capacity. It is not known to what degree, if any, topical methoxsalen is absorbed systemically. Topical methoxsalen should be used in women only when clearly indicated.

D. Nursing Mothers

It is not known whether topical methoxsalen is absorbed or excreted in human milk. Caution is advised when topical methoxsalen is used in a nursing mother.

E. Pediatric Usage

Safety and effectiveness in children below the age of 12 years have not been established.

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