What Are Adjuvant Analgesics?

Learn why antidepressants and anticonvulsants are used to treat chronic pain

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An adjuvant analgesic is a medication that is not primarily designed to control pain but can be used for this purpose. Some examples of adjuvant analgesics are medications like antidepressants and anticonvulsants. They may also be called coanalgesics.

You might be prescribed an adjuvant analgesic in addition to other pain medications, or on its own. Adjuvant analgesics tend to be less effective for musculoskeletal pain, such as back pain or joint pain.

However, they can work well for neuropathic pain and pain syndromes, such as fibromyalgia. They also have a role in treating cancer pain. Unlike many other non-opioid analgesics, adjuvant analgesics are not available over the counter.

Types of Adjuvant Analgesics

Antidepressants

While antidepressants are not often thought of as pain medication, they can effectively treat chronic pain conditions. Antidepressants are thought to control the way pain is perceived from the spinal cord to the brain. In addition, antidepressants may decrease anxiety and help regulate sleep.

However, not all types of antidepressants are effective in managing chronic pain. Tricyclic antidepressants (TCAs) such as amitriptyline, selective serotonin reuptake inhibitors (SSRIs), like duloxetine, and others, such as nefazodone, are commonly used to treat both chronic pain syndromes and nerve pain. Monoamine oxidase inhibitors (MAOIs) are not as effective in chronic pain control.

Anticonvulsants

Anticonvulsants, which are medications most commonly used to control seizure disorders, can also be used to treat chronic pain. Anticonvulsants work by not allowing certain types of nerve transmissions, and they can decrease neuropathic pain, such as those caused by trigeminal neuralgia or diabetic neuropathy.

Anticonvulsants commonly used to manage chronic pain include gabapentin and pregabalin.

Gabapentin is the most widely-used adjuvant analgesic. Some patients who don't respond well to gabapentin respond instead to pregabalin, and vice versa.

What Pain Syndromes Do Adjuvant Analgesics Treat?

The Oxford Textbook of Palliative Medicine and the Merck Manual list the following adjuvant analgesics to treat pain syndromes:

Adjuvants Used for Multiple Types of Pain Syndromes

  • Corticosteroids
  • Dexamethasone
  • Prednisone
  • Tricyclic antidepressants
  • Amitriptyline: not recommended for the elderly or patients with a heart disorder.
  • Desipramine
  • Selective serotonin and norepinephrine reuptake inhibitor (SNRI) antidepressants
  • Duloxetine: It is better tolerated than tricyclic antidepressants.
  • Milnacipran
  • Alpha-2-adrenergic agonists
  • Tizanidine
  • Topical therapies: capsaicin can be used for neuropathic pain and arthritis.
  • Local anesthetics: such as a lidocaine patch

Adjuvants Used for Neuropathic Pain

  • Antiepileptic agents
  • Gabapentin: This is the preferred drug of the anticonvulsants.
  • Pregabalin
  • Carbamazepine: this is the first-line treatment for trigeminal neuralgia.
  • Phenytoin: considered to be a second-line drug.
  • Valproic acid: used for headache.
  • Clonazepam
  • Lamotrigine
  • Topiramate
  • Tiagabine
  • Oxcarbazepine
  • Lacosamide
  • NMDA receptor antagonists
  • Memantine
  • Ketamine
  • Dextromethorphan: used when the pain has an inflammatory component.
  • Oral sodium channel blockers
  • Mexiletine
  • Tocainide
  • Baclofen: Used in trigeminal neuralgia.
  • Calcitonin

Adjuvants Use for Complex Regional Pain Syndrome

  • Calcitonin
  • Clonidine
  • Prazosin: Bone pain from cancer
  • Bisphosphonates (e.g., pamidronate)
  • Calcitonin
  • Radiopharmaceuticals

A Word From Verywell

If you wonder why different medications are being used to treat your chronic pain, ask your doctor or pharmacist to explain. The biochemistry involved can be complicated, but you can be reassured that you are receiving the correct medications that will work together to provide pain relief.

Sources

Lussier D, Portenoy RK: Adjuvant analgesics. In Doyle D, Hanks G, Cherny NI, Calman K (eds): Oxford Textbook of Palliative Medicine. Oxford: Oxford University Press, 4th Ed, Oxford: Oxford University Press, 2011.

Markman, J, et. al. Tratment of Pain. Merck Manual Professional Version. http://www.merckmanuals.com/professional/neurologic-disorders/pain/treatment-of-pain.

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