Overview

Adjuvant analgesics are drugs whose primary indication is not pain but that relieve specific pain types — especially neuropathic pain, which responds poorly to opioids and NSAIDs alone. They work best added to (not substituted for) a primary analgesic in a multimodal plan. The three major classes are anticonvulsants, antidepressants, and corticosteroids. Onset is not immediate: antidepressants and anticonvulsants may take 1-2 weeks for full analgesic effect, so the client needs education about realistic timelines.

Anticonvulsants

gabapentin

binds alpha-2-delta subunit of voltage-gated calcium channels; first-line for neuropathic pain

pregabalin

same alpha-2-delta mechanism; first-line for postherpetic neuralgia

Antidepressants

amitriptyline

tricyclic; inhibits norepinephrine + serotonin reuptake, modulating descending pain inhibition

duloxetine

SNRI; first-line for diabetic neuropathy and fibromyalgia

Corticosteroids

dexamethasone

reduces inflammation/edema around nerves and tumors; key adjuvant in cancer pain and acute spinal cord compression

Indications

neuropathic pain Hallmark

burning, shooting, electric pain; responds poorly to opioids alone

diabetic peripheral neuropathy

first-line: duloxetine or gabapentin/pregabalin

postherpetic neuralgia

first-line: gabapentin or pregabalin

fibromyalgia

duloxetine

cancer-related pain

corticosteroid adjuvant for nerve/tumor edema

acute spinal cord compression

dexamethasone

Administration & Monitoring

add to a primary analgesic, do not substitute

adjuvant role within a multimodal plan

titrate gabapentin gradually over 1-2 weeks

minimizes sedation, dizziness, ataxia

reduce gabapentin/pregabalin dose in renal impairmentCrCl < 60 mL/min

renally cleared; accumulates in renal impairment

assess for dizziness and sedation

fall risk, especially in older adults

monitor blood pressure on duloxetine

norepinephrine reuptake inhibition can raise BP

monitor mood for suicidal ideation

SNRI/antidepressant monitoring requirement

limit cyclobenzaprine to short-term spasm

not for chronic pain; additive CNS depression with gabapentin

Patient Teaching

full pain relief may take 1-2 weeks

not immediate after the first dose

do not stop gabapentin abruptly

taper to discontinue

rise slowly to avoid falls

dizziness, sedation, ataxia

avoid combining sedating drugs

additive CNS depression

report worsening mood or suicidal thoughts

while on antidepressant adjuvants

Report Nowescalate immediately

excessive sedation Hallmark

Pasero sedation score ≥3; gabapentinoid + opioid additive CNS/respiratory depression (2019 FDA warning)

respiratory depression

amplified by obesity and obstructive sleep apnea with gabapentinoid + opioid

new or worsening suicidal ideation

antidepressant adjuvants

severe dizziness or unsteady gait

fall risk in older adults

Clinical Pearl

Burning, shooting, or electric pain screams neuropathy — reach for gabapentin or duloxetine, not more morphine. Opioids alone won't silence a misfiring nerve, and these adjuvants take 1-2 weeks to fully work.

Adjuvant Pain Medications