Pharmacological Treatment of Neuropathic Pain and Depression

Medication Overview

• Amitriptyline is a dual-acting tricyclic antidepressant (TCA) that inhibits both serotonin and norepinephrine reuptake, according to the American College of Neuropsychopharmacology 1
• Mirtazapine is an antidepressant that can promote sleep, appetite, and weight gain, with sedative effects most pronounced at lower doses, as recommended by the American Academy of Family Physicians 2, 3

Treatment of Neuropathic Pain

• The National Comprehensive Cancer Network recommends amitriptyline as a first-line coanalgesic for cancer-related neuropathic pain, with a starting dose of 10-25 mg nightly, which can be increased to 50-150 mg nightly 4

Treatment of Depression

• The American College of Physicians suggests that for patients with two or more episodes of depression, longer duration of therapy may be beneficial 5
• Treatment with mirtazapine should continue for 4-9 months after satisfactory response for the first episode of depression, with longer duration potentially beneficial for recurrent depression, as recommended by the American Academy of Family Physicians 6, 2
• The optimal antidepressant dose of mirtazapine is typically 30-45 mg daily, with lower doses (15 mg) tend to be more sedating due to predominant H1 antagonism, as recommended by the National Institute of Mental Health 7

Dosing and Administration

• Mirtazapine should be started at a dose of 15 mg once daily in the evening prior to sleep, with titration up to 30 mg at bedtime as needed for optimal antidepressant effect, as recommended by the American Academy of Family Physicians 2
• Elderly patients may require lower starting doses (7.5-15 mg) due to reduced clearance, and patients with hepatic or renal impairment may also require dose adjustments, as recommended by the American Geriatrics Society 5
• Strong CYP3A inducers may require mirtazapine dose increase, and strong CYP3A inhibitors may require mirtazapine dose decrease, to optimize the therapeutic benefits of mirtazapine while minimizing potential side effects 2, 3

Monitoring and Safety

• Assess therapeutic response after 4-8 weeks on the current regimen, monitoring for sleep quality, daytime sedation, sexual function improvement, weight changes, and mood and anxiety symptoms, using standardized depression scales, as advised by the American Academy of Family Physicians and the American Heart Association 2, 6
• Regular monitoring is recommended to check blood pressure, weight, and metabolic parameters periodically, and to assess for side effects, particularly signs of serotonin syndrome, as advised by the American Heart Association 6
• The following adverse effects and their frequencies have been reported for mirtazapine:

• Lamotrigine may cause serious rash, including Stevens-Johnson syndrome, with a risk of 0.1%, as reported by the CDC 8
• Mirtazapine may cause rare hematological effects, such as agranulocytosis and neutropenia, as reported by the AACAP 9
• Varenicline carries a warning for potential neuropsychiatric side effects, including depression and suicidal ideation/behavior, and is contraindicated in patients with brain metastases due to seizure risk, according to the National Comprehensive Cancer Network 10

Contraindications and Interactions

• MAOIs should be avoided with mirtazapine due to the risk of serotonin syndrome, as recommended by the AACAP 9
• The combination of lamotrigine and mirtazapine does not increase the risk of serotonin syndrome, as reported by the American Academy of Child and Adolescent Psychiatry (AACAP) 9
• The combination of Chantix (varenicline), Lamictal (lamotrigine), and sumatriptan requires monitoring for individual safety considerations, including neuropsychiatric effects, seizure risk, and common side effects, as recommended by the National Comprehensive Cancer Network 10