The value of antimetabolites for psoriasis was first observed by Gubner.1 He pointed out that the suppressive effects of aminopterin were much greater on epithelium than on blood-forming organs.
Aminopterin (4-aminopteroylglutamic acid) is a metabolically useless analogue of folic acid. Folic acid is necessary for normal cell reproduction because it is converted in the body to folinic acid (citrovorum factor) which participates in several essential biochemical reactions. Aminopterin competes with folic acid to prevent its conversion to folinic acid and also competes with folinic acid in its biochemical reactions.2 Methotrexate (4-amino-N10-methylpteroylglutamic acid) is another folic acid antagonist related to aminopterin in structure. Methotrexate tablets contain 5 times the concentration of drug as aminopterin tablets, but produce fewer toxic reactions.
The pathologic state of the epidermis in psoriasis is one of excessive mitotic activity and incomplete cellular maturation. The benefit of both topically and systemically used therapeutic agents can
REES RB, BENNETT JH. Methotrexate vs. Aminopterin for Psoriasis. Arch Dermatol. 1961;83(6):970–972. doi:10.1001/archderm.1961.01580120082020
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