Individual patients vary greatly in their response to different opioids - the biological basis for the individual variability in sensitivity to opioids is multifactorial.
Patients who obtain poor response to one opioid will frequently tolerate another opioid.

Opioid rotation (sequential opioid trials, also opioid switching) may be needed to identify the drug that yields the most favorable balance between analgesia and adverse effects.

The need to change opioid occurs in the following clinical conditions:
- pain is controlled but the patient experiences intolerable adverse effects
- pain is not adequately controlled, but it is impossible to increase the dose due to adverse effects
- pain is not adequately controlled by rapid increasing the dose of opioids, although the drug does not produce adverse effects.

Studies suggest that
(a) about 12% of patients may require a true opioid rotation (excluding changes of route), due to insufficient efficacy (64%), adverse effects (51%), or application problems (22%), and
(b) opioid rotation will result in clinical improvement at least in more than 50% of patients with chronic pain presenting a poor response to one opioid.

Mercadante S and Bruera E. Opioid switching: A systematic and critical review. Cancer Treatment Reviews, 2006. 32, 304.