Case Reports of Transdermal Fentanyl Patch Administration Difficulties in Cancer Patients with Excess Sweating.

(Case 1) A 45-year-old male was diagnosed with prostate cancer. Treatment was administered using bicalutamide and leuprorelin acetate, while a transdermal fentanyl (TDF) was applied for pain relief. However, TDF continued to peel off owing to excessive sweating, even when reinforced by a protective layer. As such, TDF was discontinued and pain control was initiated using other medicines. Sweating occurred irregularly because of hot flashes, approximately four to five times per day. (Case 2) A 37-year-old male was diagnosed with a malignant thymoma and sacral metastasis. For analgesic control, etodolac tablets, carbamazepine tablets, and TDF were administered. Subsequently, the dose of the TDF was gradually increased, but the analgesic effect was low; thus, fentanyl blood concentration was measured. The measurements showed that even higher TDF doses did not increase fentanyl blood levels. During this period, full body sweating began to occur to a large extent due to unknown causes, and it was thought that the absorption of fentanyl decreased. When using a TDF, it is necessary to monitor patients for any sweating during treatment, while also considering changes in medication in some cases. This should promote the maintenance and improvement of the quality of life of the affected patients.