Why Long-Acting Opioids Can Make Pain Worse

There is a quiet paradox in chronic pain care: the patient whose dose keeps climbing while the pain keeps worsening. It is usually read as disease progression or drug-seeking. Often it is neither. It is pharmacology doing exactly what it does when a receptor is never allowed to rest.

The receptor needs to cycle

The mu-opioid receptor is a G-protein-coupled receptor. Its regulation depends on phosphorylation of the C-terminal tail domain, which recruits beta-arrestin proteins and drives receptor internalisation. That cycle — activation, internalisation, resensitization, return to the surface — is not a defect. It is how the system stays responsive.

When an agonist is constantly present, the loop cannot complete. The receptor desensitizes and uncouples, and the signal it was built to carry degrades.

How that becomes more pain, not less

The downstream consequence is opioid-induced hyperalgesia — a paradoxical increase in pain sensitivity despite escalating doses. The patient hurts more, so the dose rises, so the receptor is occupied more continuously, so sensitivity increases further.

Alongside it runs central sensitization: the nervous system amplifying signals it once filtered. The analgesic return diminishes while the underlying pain state worsens.

Why long-acting formulations are the harder problem

Short-acting and long-acting opioids are not simply different schedules of the same drug. Long-acting agents produce near-continuous receptor occupancy, and in doing so they deny the nervous system the pharmacological rest periods required for resensitization and homeostasis.

Chronic exogenous stimulation also suppresses the body’s own production of endorphins and enkephalins. The endogenous system becomes less responsive to natural stimuli such as stress or physical activity, and patients lose the capacity for innate pain and mood modulation — a state best described as physiological insolvency. The external supply is losing power at the same time the internal supply is being spent down.

The pill-count paradox

Here is where clinical reality collides with metrics. Enforcement headlines quote raw tablet numbers, which pushes dispensing partners to encourage fewer units. The straightforward way to reduce unit count is to consolidate a patient onto longer-acting medication — which improves the prescribing ratio on paper while producing exactly the continuous receptor occupancy described above.

A lower pill count is not the same as a lower risk. We would rather defend a higher unit count at a genuinely low total morphine-equivalent dose than accept a tidier number achieved through receptor saturation. Our full protocol is set out for dispensing partners in our opioid stewardship guide.

What we do instead

We do not offer medication-only management. Opioids, where used at all, sit inside an interventional and metabolic program, at doses we work continuously to reduce — typically under 30–40 MME, with an average nearer 27–32.5 MME.

Restoring the endogenous system matters as much as reducing the exogenous one. Sleep and circadian health are central to that, because deep sleep is when the body recharges its own pain-relieving chemistry — see circadian rhythm disruption and chronic pain and artificial light at night.

Frequently asked questions

What is opioid-induced hyperalgesia?

It is a paradoxical state in which pain sensitivity increases despite escalating opioid doses. It arises when continuous receptor occupancy causes desensitization and uncoupling of the mu-opioid receptor, so the same or higher dose produces less relief and greater sensitivity. Individual results vary.

Does this mean opioids are always harmful?

No. Opioids have a legitimate role, particularly in acute, cancer and perioperative pain. The concern is chronic, continuous exposure without a plan to reduce it, and especially long-acting formulations that never allow receptor resensitization. Do not start, stop, or change any prescribed medication on your own — that decision belongs with your physician.

If my pill count went down, isn’t that safer?

Not necessarily. Unit count and pharmacological risk are different measures. Consolidating onto longer-acting medication lowers the tablet number while increasing continuous receptor occupancy. Total morphine-equivalent dose and the pattern of exposure matter more than the number of tablets.

Where are you located and how do I make an appointment?

Padda Institute Center for Interventional Pain Management, 4477 Woodson Road, Suite 100, St. Louis, MO 63134. Book at painmd.tv/appointment/ or call (314) 481-5000.

Key takeaways

• The mu-opioid receptor depends on a cycle of internalisation and resensitization to stay responsive.
• Continuous agonist presence causes desensitization, contributing to opioid-induced hyperalgesia.
• Long-acting formulations deny the nervous system the pharmacological rest that cycle requires.
• Chronic exposure also suppresses endogenous endorphins — a state of physiological insolvency.

Medically reviewed by Dr. Gurpreet Singh Padda, MD, MBA, MHP — Board Certified in Anesthesiology, Pain Medicine, Interventional Pain Management, Addiction Medicine, and Obesity Medicine. Last reviewed July 2026.

This article is educational and is not a substitute for evaluation, diagnosis, or treatment by a physician. Individual results vary. Do not start, stop, or change any medication without consulting your physician.

References

1. Birdsong et al. (2015) — mu-opioid receptor phosphorylation and beta-arrestin recruitment. (Confirm full citation.)
2. Woodbury (2015) — opioid-induced hyperalgesia and central sensitization. (Confirm full citation.)
3. Mercadante (2017) — opioid-induced hyperalgesia in clinical practice. (Confirm full citation.)
4. Clauw (2017) — endogenous opioid suppression and receptor resensitization. (Confirm full citation.)

Dr. Gurpreet Singh Padda, MD, MBA, MHP , MD, MBA, MHP