Adjuvant pain medications are medications that are not typically used for pain but may be helpful for its management. Adjuvant pain medications can include antidepressants, anti-seizure medications, muscle relaxants, sedatives or anti-anxiety medications, and botulinum toxin.


Some antidepressants (e.g., amitriptyline, nortriptyline, venlafaxine, duloxetine) may be helpful for nerve-related pain called neuropathic pain, for migraine headaches, fibromyalgia, and rheumatoid arthritis. Usually, lower doses than those needed to treat depression are effective for pain. Just because antidepressants are helpful for pain does not mean that the pain is caused by depression. People who do not have depression can experience pain relief with these medications and people with depression may not experience pain relief.

Antidepressants are thought to work by increasing the levels of certain chemicals (norepinephrine, serotonin) at nerve endings that help to inhibit pain signals. Some people with chronic pain may also experience depression. In these cases, treatment with antidepressants can improve quality of life, but without having an effect on pain control. The most common side effects of antidepressants used for pain control are drowsiness, dry mouth, and constipation.

Anti-seizure medications

Anti-seizure medications such as gabapentin, pregabalin, topiramate, lamotrigine, and carbamazepine may also be helpful for nerve-related pain. The most common side effects with these medications are drowsiness, dizziness, and balance problems, but they usually improve with continued use.

Muscle relaxants

Muscle relaxants such as baclofen, cyclobenzaprine, methocarbamol, and diazepam may also be used to help with pain management. However, their use is best limited to short-term periods of worsening pain due to tense muscles. Muscle relaxants have not been proven to be effective for the management of chronic pain.

Sedative and anti-anxiety medications

Getting enough sleep can be difficult for people who are in pain. Doctors may prescribe medications such as zopiclone, lorazepam, or temazepam to help with short-term sleep problems. These medications should only be used for a short period of time because they can be habit-forming and become less effective with chronic use.

If you are experiencing severe anxiety, this can make your pain worse and your doctor may suggest counselling or an anti-anxiety medication (e.g., lorazepam, alprazolam) to help. Do not drink alcohol if you are taking medication for anxiety or sleep as this can cause extreme drowsiness and can reduce breathing.

If you have been taking a medication for sleep or anxiety, do not stop it suddenly without talking to your doctor. If you stop your medication suddenly you may experience withdrawal symptoms. If you have ongoing problems with sleeping, your doctor may prescribe other mediations (e.g., antidepressants) to help.

If you have pain that is not controlled by common pain medications, ask your doctor if any adjuvant medication would help.

Botulinum toxin

If you thought Botox® was used only for cosmetic purposes, think again. Botulinum toxin type A - known commercially as Botox® - is also used to treat muscle spasticity associated with strokes and cerebral palsy and was recently approved in Canada to prevent chronic migraine headaches (headaches more than 14 days a month). Injections are also being used to treat other types of pain, although not enough evidence is available to support its use at this time.

Essentially, botulinum toxin works by blocking the nerves from releasing acetylcholine, a substance that causes muscles to contract. This results in temporary paralysis of the affected muscle that typically lasts up to 3 months. For chronic migraine prevention, injections are given approximately every 3 months and are injected into muscles around the head and neck. For muscle spasticity, botulinum toxin is injected into affected muscles.

The side effects for any of these treatments are minimal (e.g., muscle weakness), but there is a possibility that botulinum toxin can spread to other parts of the body and cause vision changes, eyelid drooping, and bronchitis.