Skin patches used in Hormone Replacement Therapy (HRT). A double and single transdermal skin patch, brand name Estraderm TTS, manufactured by Ciba- Geigy. These self-adhesive skin patches are impregnated with 10 and 4 milligrams respectively of the female hormone oestradiol (a type of oestrogen). They each release some 50 micrograms oestradiol in 24 hours when in contact with the skin. The double patch also releases Norethis- terone acetate. Oestrogen replacement therapy is typically given to relieve menopausal symptoms in women. These symptoms can include hot flushes, night sweating, and atrophic vaginitis. HRT also helps prevent atherosclerosis and osteoporosis.