Medrysone (INN, USAN) (brand names HMS, Medrocort, others; former developmental code name NSC-63278), also known as hydroxymethylprogesterone, methylhydroxyprogesterone, or hydroxymesterone, as well as 6α-methyl-11β-hydroxyprogesterone or 6α-methyl-11β-hydroxypregn-4-ene-3,20-dione, is a synthetic glucocorticoid that is or has been used in the treatment of inflammatory eye diseases. It has been discontinued in the United States. Although it is very similar in structure to progesterone, neither progestogenic nor androgenic activity has been demonstrated for or attributed to medrysone.