Use of Fentanyl Patch in Partial Doses Than the Original

A sample of 95 patients will be recruited. Once consent form is signed, blood samples will be collected twice: 1. At the time of the visit; 2. After 144 hours (about 6 days) from the first sample, and at least 36 hours after replacing the cut patch. Pain management will be evaluated at both visits using the Brief Pain Inventory (Hebrew version) - BPI questionnaire, and rescue doses used before and after the cutting of the patch. The blood samples will be transferred to the laboratory for testing of fentanyl concentration levels.