Study Objective: The objective of our study was to determine safety and pharmacology (pharmacokinetics and preliminary efficacy) of intranasal (IN) ketamine for uncontrolled cancer-related pain. Design: Dose escalation clinical trial. Setting: Outpatient. Patients: Ten adult patients with uncontrolled cancer-related pain. Intervention: Each patient received escalating doses of ketamine over four visits, each 2-5 days apart: 10 mg IN at visit 1, 10 mg intravenous (IV) at visit 2, 30 mg IN at visit 3, and 50 mg IN at visit 4. Measurements: Pain was measured before and after drug administration for up to 4 h using the 11 point (0-10) Numerical Pain Rating Scale (NPRS).Main Results: All subjects had advanced cancer, with intractable pain, despite being on moderate dosage of opioids. There was a statistically significant reduction in median NPRS by 1.5 (1-4), 3 (2-3), and 4 (3-5) points at 60 min after receiving the medication and remained decreased by 1.5 (1-2), 2 (1-2) and 1 (1-4) points at the end of the study visit (240 min) with the 10 mg, 30 mg and 50 mg IN dosage, respectively. The