Fentanyl is considered a potent synthetic opioid widely used in anesthesiology, for short and long-term pain management, and for sedation. The fentanyl patch is constructed like a matrix, a system based on a polyacrylate net with fentanyl that attaches directly onto the skin. The doses available today are from 12µg/h, 25, 50, 75, to 100 µg/h. Despite the variable doses available, often in certain patients as the elderly or children, there is a need for slower titration than the 12 µg/h currently available.

In this study, the investigators aim to evaluate pain control and to examine the blood fentanyl concentration of patients on a fix dose of fentanyl patch up to 100 µg/h every two or three days, and compare it with pain control and concentration levels obtained from a similar dose patch, but after cutting the patch into two.

The study will take place at the pain clinic of Clalit Health Services-South District (CHS-SD), and the Negev home palliative care unit. In CHS-SD there are approximately 300 patients treated regularly with opioids and about 120 patients in the home palliative care unit. 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.

Inclusion Criteria:

• patients suffering from chronic pain on a fixed dose of fentanyl patch for over two weeks, with a maximum dose of 100 µg/h every two or three days, and have given their informed consent will be included in the study.

Exclusion Criteria:

• Patients with cognitive problems
• non-Hebrew speaking
• patients that their medical condition prevents them from participation in the study.