Customer: replied 6 years ago. My doctor said fentanyl patch is 100 times stronger than morphine this is confusing. plus i am still in a pain range of about a 7. Expert: Dr. P. Jyoti replied 6 years ago.Transdermal Fentanyl, the fentanyl patch, has an onset of action of 6-12 hours, that is, it takes this long to get into the system and give pain relief.In case of opioids, the comparision is made not in terms of which is stronger but in terms of the dose which is required to have the same analgesic effect.ustomer: replied 6 years ago. My doctor said fentanyl patch is 100 times stronger than morphine this is confusing. plus i am still in a pain range of about a 7. Expert: Dr. P. Jyoti replied 6 years ago.