Introduction
cancer, cancer pain, Pain, pain
CANCER, CHRONIC PAIN
Pain is a common symptom in cancer patients; some studies suggested that almost half of patients experience pain at least 3 months after completing curative treatment, and nearly a third experience moderate to severe pain [Clinical guidelines for managing cancer pain, including those developed by the World Health Organization (WHO) [Tramadol is a weak μ-opioid receptor agonist that also inhibits norepinephrine and serotonin reuptake, with proven efficacy for managing chronic pain. Oral administration is preferred, with a regular dosing frequency every 4 or 12 h depending on the formulation prescribed (e.g., immediate-release or extended-release formulations). However, another administration route may be required in some patients.With a view to improving the pharmacokinetic profile of orally administered tramadol, Nippon Zoki developed a new tramadol formulation as bilayer sustained-release (SR) tablets (hereafter bilayer tablets) in which the top layer comprises 35% of the dose as an immediate-release (IR) formulation and the lower layer comprises 65% of the dose as a SR formulation administered twice-daily (Twotram