1.Start with a specific drug for a specific type of pain. As defined by the WHO three-step analgesic ladder, the specific drug chosen depends in part on the degree of pain intensity and the type of pain. Cancer patients commonly have multiple sites and types of pain. A continuum of opioid responsiveness, rather than an all-or-none phenomenon, has been clearly observed. opioid responsiveness is defined as the degree of analgesia achieved during dose escalation to either intolerable side effects or adequate analgesia. Patient characteristics and pain-related factors, as well as drug-selective effects, influence this variable response.