Hi, severe pain can be very distressing. It is important that pain is managed effectively with proper & safe drugs. The drug Fentanyl prescribed to you is an opioid & is 100 times more effective than morphine. Fentanyl patches are approved for use in long standing pain. Fentanyl patch is ideal for your condition. Generally, it may take 12 hours to get pain relief and 16 hours to get full benefit by Fentanyl patch but this varies from person to person. Don t apply heat on the patch as that may increase the absorption of fentanyl & may result in its overdose. Hydrocodone is a morphine derivative. Overdose of Fentanyl & Hyrocodone can result in dangerous side effects like respiratory arrest. Hence it is wise not to take Hydrocodone with Fentanyl patch. Some non opioid drugs like Diclofenc, Ketorolac & Etodolac also can provide pain relief comparable to the relief produced by Hydrocodone & these drugs are safer compared to opioids. So, if Fentanyl s action is delayed, then you can take one of the above mentioned drugs & not Hydrocodone.