According to the WHO Guideline on Cancer Pain Relief (second edition), pain treatment should consist of three steps:

Step 1: For mild pain: non-opioid analgesics (e.g., paracetamol), to which an adjuvant can be added if necessary.
When a non-opioid no longer adequately controls the pain, an opioid analgesic should be added.

Step 2: For mild to moderate pain: weak-acting opioid analgesics, to which non-opioid analgesics and adjuvants can be added if necessary.
If the pain is persisting or increasing, proceed to Step 3.

Step 3: For moderate to severe pain: strong-acting opioids, to which non-opioid analgesics and adjuvants can be added if necessary.
If the pain is increasing, the dosage of the opioid should be increased in steps until the patient is free of pain. The effective analgesic dose of morphine varies considerably and ranges from as little as 5 mg to more than 1000 mg every 4 hours. The effective dose varies partly because of individual variations in systemic bioavailability. The correct dose is the dose that works.

Five principles on managing pain
The five principles on managing pain are also part of this method:

1. By mouth, meaning that oral administration if possible is preferred.
2. By the clock, meaning that administration should be given in regular intervals and one should not wait for the pain to return.
3. By the ladder, as explained above.
4. For the individual, as opioid kinetics vary tremendously from person to person, one cannot prescribe standard dosages.
5. Attention to detail should be given.

WHO. Use of controlled medications in pain treatment. Internet. Accessed on January 24, 2016.