One major difference between anti-inflammatories and opioid analgesics is that the former have a “ceiling effect” — that is, continuous dose escalation does not provide concomitant escalation in pain relief.
One reason opioids are so useful in the treatment of chronic pain is that as tolerance to a dose develops, the dose can be raised. In fact, there is no limit to how high opioid dosing can go -– keeping in mind that higher doses can be associated with unpleasant and/or even dangerous side effects.