Mylan Technologies has received the first approval from the FDA for a generic version of Alza's Duragesic Patch (Fentanyl Transdermal System), which is indicated to treat patients suffering from severe chronic pain who can't be managed with alternative analgesics. The transdermal patch delivers fentanyl for slow absorption into the body, providing pain relief for up to 72 hours.The generic transdermal fentanyl patches are available in 25 mcg/h, 50 mcg/h, 75 mcg/h, and 100 mcg/h sizes. The patches are translucent and rectangular. The Mylan product is a Schedule II controlled substance.