Sustained release hormonal preparations. I. Diffusion of various steroids through polymer membranes

Various steroids diffused readily through dimethylpolysiloxane membrane into distilled water at 37°C. The diffusion was found to be proportional to the thickness of the membrane and its area. Calculated values for standard conditions (μg/24 hrs/100mm2/0.1mm) were as follows: 19 norpregn-4-ene-3, 20-dione, 1353; pregn-4-ene-3, 20-dione, 469; 17β-hydroxyandrost-4-en-3-one, 317; 6-methyl-17α-acetoxypregna-4, 6-diene-3, 20-dione, 236; 17α-ethynyl-17β-hydroxyestr-4-en-3-one, 73; estra-1, 3, 5(10)-triene-3, 17β-diol, 61; 3-methoxy-17α-ethynylestra-1, 3, 5(10)-trien-17β-ol, 43; 11β, 21-dihydroxypregn-4-ene-3, 20-dione, 21; 11β, 17α, 21-trihydroxypregn-4-ene-3, 20-dione, 6. The rates of diffusion through other polymers (acetylcellulose, fluoroethylene, polyester, polycarbonate, polyethylene, polyamid, and polystyrene copolymer) were of the order of 1% or less.