The case study presents a 75-year-old female patient treated at the Outpatient Clinic Prosen. The patient with advanced cancer disease participated in a clinical trial that aimed at evaluating the efficacy and safety of treatment with intranasal fentanyl used for treating breakthrough pain episodes. The study protocol assumed participation in the open label phase of treatment as long as thepatient's clinical situation required. Then, the treatment was continued with the drug being available and refundable an outpatient basis. The patient have been treated with the study medication (Instanyl) in stable doses since 2007. The present case study of a long-term Instanyl treatment proved effective, safe and significantly improved the quality of life of the patient in question.