Major Categories of Adjuvant Analgesics
Anticonvulsants
- Gabapentin (Neurontin) and pregabalin (Lyrica) are first-line treatments for neuropathic pain by blocking calcium channels and reducing nerve excitability. Common side effects include dizziness, sedation, and peripheral edema.
- Monitor for suicidal ideation in patients taking anticonvulsants, especially during the first few weeks of therapy or dose changes.
Memory Aid: "GAB-A-pain away" - Gabapentin for neuropathic pain
Antidepressants
- Tricyclic antidepressants (TCAs) like amitriptyline and nortriptyline block sodium channels and enhance descending pain inhibition pathways. They're particularly effective for neuropathic pain and fibromyalgia.
- SNRIs (duloxetine, venlafaxine) inhibit serotonin and norepinephrine reuptake, making them effective for diabetic neuropathy and fibromyalgia with fewer anticholinergic side effects than TCAs.
TCAs have significant anticholinergic effects: dry mouth, constipation, urinary retention, and cardiac conduction delays
Topical Agents
- Capsaicin cream depletes substance P from nerve endings, providing relief for arthritis and neuropathic pain with minimal systemic absorption. Patients should wash hands thoroughly after application and avoid contact with eyes and mucous membranes.
- Lidocaine patches provide localized anesthesia for post-herpetic neuralgia and localized neuropathic pain with minimal systemic effects when used as directed.
Clinical Applications
Clinical Scenario
A 65-year-old diabetic patient complains of burning, tingling pain in both feet that worsens at night. Traditional NSAIDs provide minimal relief.
Appropriate adjuvant analgesics: Gabapentin or pregabalin (first-line), duloxetine (especially if concurrent depression), or topical capsaicin for localized relief.
Nursing Considerations
- Assess pain characteristics: burning, shooting, tingling suggests neuropathic pain suitable for adjuvant therapy
- Start with low doses and titrate gradually to minimize side effects and improve tolerance
- Educate patients about delayed onset of action (days to weeks) to prevent premature discontinuation
- Monitor for drug interactions, especially with anticonvulsants and antidepressants
- Assess for mood changes and suicidal ideation with anticonvulsants and antidepressants