If you use a 25 mcg/hour fentanyl patch, you’ll want to check to see if it’s on this Actavis recall:

Actavis identified one lot of 25 mcg/hour Fentanyl patch (Control/Lot # 30349) shipped to market that contained one patch that released its active ingredient faster than the approved specification in laboratory testing. An accelerated release of Fentanyl from a 25 mcg/hour patch can lead to adverse events for at-risk patients, including excessive sedation, respiratory depression, hypoventilation (slow breathing), and apnea (temporary suspension of breathing). The patches are packaged individually and boxed in quantities of five patches per box.

Recalled Control/Lot #s

30041, Exp 12/2011
30258, Exp 03/2012

30049, Exp 12/2011
30349, Exp 03/2012

30066, Exp 12/2011
30350, Exp 03/2012

30096, Exp 01/2012
30391, Exp 03/2012

30097, Exp 02/2012
30392, Exp 04/2012

30123, Exp 01/2012
30429, Exp 04/2012

30241, Exp 02/2012
30430, Exp 04/2012

30256, Exp 02/2012
30431, Exp 04/2012

30257, Exp 03/2012
30517, Exp 04/2012

Source: Recalls, Market Withdrawals, & Safety Alerts > Actavis Inc. Issues a Voluntary Recall of 18 Lots of Fentanyl Transdermal System 25 mcg/h

I would also suspect that a defective fentanyl patch like this could lead to death from acute fentanyl intoxication.  If you have a recalled patch, definitely click the link above to the FDA and follow the directions on exchanging the patches.