Introduction
Postherpetic neuralgia (PHN) is a chronic pain condition that arises as a complication of herpes zoster, more commonly known as shingles.1–3 Shingles occurs when the varicella-zoster virus is reactivated later in life, typically due to immunocompromise. While shingles itself can cause significant discomfort, it is usually self-limited and resolves within a few weeks. However, in some individuals, the pain persists for months or even years, leading to the condition known as postherpetic neuralgia (PHN).4,5 The pain associated with PHN is described as severe, burning, and often intolerable, significantly impairing patients’ quality of life and ability to perform daily activities.5,6
PHN develops in a percentage of individuals who develop shingles, with the risk increasing with age. The likelihood of developing PHN is particularly high in individuals over the age of 50, making it a common pain condition in older adults.7,8 Despite the availability of antiviral medications that can shorten the course of shingles, the risk of developing PHN remains, especially in cases where treatment is delayed or when the initial rash is severe.9,10
The nature of PHN pain is neuropathic, characterized by damage to the peripheral nerves.4,6 This damage leads to aberrant pain signaling pathways, where patients experience pain in response to stimuli that would not normally cause discomfort, such as light touch or clothing brushing against the skin. PHN is also known for spontaneous pain episodes, where patients feel intense discomfort without any external trigger. The chronic nature of the pain can lead to significant emotional and psychological distress, with many patients developing anxiety, depression, or sleep disturbances due to the persistent nature of the pain.
The management of PHN is challenging, as the pain is often refractory to traditional analgesics. First-line treatments include anticonvulsants like gabapentin and pregabalin, which work by stabilizing hyperexcitable nerve membranes, and topical treatments such as lidocaine patches or capsaicin cream.6,11–13 Opioids may be used in more severe cases, but they come with the risk of addiction and side effects like sedation and respiratory depression, particularly in older adults. When these treatments fail, tricyclic antidepressants (TCAs) such as amitriptyline and nortriptyline are often considered. TCAs have demonstrated efficacy in neuropathic pain conditions, likely due to their ability to inhibit the reuptake of norepinephrine and serotonin, both of which play a role in modulating pain pathways in the central nervous system.14,15
This case series explores the use of TCAs in four patients with PHN who had failed multiple other treatment options. Despite the challenges in managing PHN, these patients achieved notable pain relief and improved quality of life with the addition of TCAs to their treatment regimens.
Case Discussion
This case series includes four patients, aged 66 to 71, all of whom had postherpetic neuralgia following shingles. They had previously tried multiple pain management strategies, including acetaminophen (APAP), nonsteroidal anti-inflammatory drugs (NSAIDs), lidocaine patches, gabapentin, pregabalin, and opioids, but none of these treatments provided adequate relief.
The first patient was a 66-year-old male who had tried APAP, NSAIDs, lidocaine patches, gabapentin, and pregabalin without success. He finally found moderate analgesic benefit with pregabalin 150 mg three times daily (TID) and amitriptyline 50 mg at bedtime. His pain improved from 10/10 on the NRS to 5/10, and he reported his pain to be much more tolerable. Notably, he experienced no side effects from the medication.
The second patient, a 71-year-old female, had failed multiple treatments, including APAP, NSAIDs, lidocaine patches, gabapentin, and tramadol. She eventually achieved significant pain reduction with a regimen of gabapentin 400 mg in the morning, 400 mg in the afternoon, 800 mg at bedtime, and nortriptyline 20 mg at bedtime. Her pain decreased from 9/10 to 4/10 on the NRS. She reported mild sedation with nortriptyline, but this side effect was beneficial as it helped her sleep better.
The third patient, a 69-year-old male, had also failed to respond to APAP, gabapentin, pregabalin, and hydrocodone. He experienced pain relief with pregabalin 100 mg twice daily (BID) and amitriptyline 25 mg BID. His pain improved from 10/10 to 5/10 on the NRS. Initially, he experienced dry mouth when starting the TCA, but this side effect resolved with continued use.
The final patient was a 68-year-old female who had tried and failed multiple treatments, including APAP, NSAIDs, gabapentin, tramadol, acetaminophen-codeine, and hydrocodone. She finally found relief with gabapentin 600 mg TID, hydrocodone 7.5 mg TID, and nortriptyline 30 mg at bedtime. Her pain decreased from 10/10 to 5/10 on the NRS, and she reported no side effects from the regimen.
The outcomes of patients treated with TCAs are visually represented in Figure 1.
Discussion
Postherpetic neuralgia is a chronic, often debilitating pain condition that can have a significant impact on a patient’s quality of life. The pain is typically neuropathic in nature, which makes it resistant to many standard pain medications, such as NSAIDs and opioids.3,6 As seen in this case series, even medications commonly used for neuropathic pain, such as gabapentin and pregabalin, may not always provide sufficient relief. This is where TCAs may have a role in the management of PHN.14,15
TCAs, such as amitriptyline and nortriptyline, have been found to be effective in treating various types of neuropathic pain, including PHN. The mechanism of action for TCAs in pain relief is thought to be related to their ability to inhibit the reuptake of norepinephrine and serotonin, two neurotransmitters that are involved in the modulation of pain signals in the central nervous system.14–16 By increasing the levels of these neurotransmitters, TCAs may help to dampen the hyperactive pain signals that are characteristic of neuropathic pain conditions.
In addition to their analgesic properties, TCAs may also improve mood and help with sleep, both of which can be severely affected by chronic pain conditions like PHN. This dual benefit is particularly important in older adults, who are at increased risk of both chronic pain and depression.17
However, TCAs are not without their side effects. Common side effects of TCAs include sedation, dry mouth, constipation, and urinary retention, which are primarily related to their anticholinergic properties.15,17,18 In older adults, these side effects can be particularly problematic, as they may exacerbate issues such as falls, confusion, and urinary retention. Therefore, TCAs must be used cautiously in this population, starting at lower doses and titrating up slowly to avoid severe side effects.
In this case series, two patients experienced side effects from their TCA treatment. One patient reported sedation with nortriptyline, which she found beneficial as it improved her sleep. Another patient reported dry mouth when starting amitriptyline, but this side effect resolved with continued use. Importantly, all four patients experienced significant reductions in their pain intensity after adding a TCA to their treatment regimen. This suggests that, despite the potential for side effects, TCAs can provide meaningful pain relief in patients with PHN, particularly when other treatments have failed.
Limitations
This case series highlights the potential utility of TCAs in managing PHN after other treatment options have failed. However, several limitations should be considered when interpreting these results. First, the small sample size of only four patients restricts the generalizability of the findings. A larger study population would be needed to more accurately assess the efficacy and side effect profile of TCAs in a broader group of patients with PHN. Additionally, the case series lacks long-term follow-up, which is crucial in understanding the sustained effectiveness of TCAs in treating PHN. Neuropathic pain conditions like PHN are often chronic, and while patients may experience initial pain relief, it is unclear whether the benefits of TCAs are maintained over months or years. While this case series provides valuable insights into the use of TCAs for PHN, larger, controlled studies with long-term follow-up are required to fully understand the role and limitations of these medications in chronic neuropathic pain management.
Conclusion
This case series demonstrates the effectiveness of tricyclic antidepressants in managing postherpetic neuralgia in patients who failed to achieve adequate relief with more conventional treatments. Amitriptyline and nortriptyline, when combined with other medications like gabapentinoids resulted in notable pain reduction and improved patient satisfaction. While side effects like sedation and dry mouth were reported, they were generally manageable and did not detract from the overall efficacy of the treatment. Further studies are needed to fully explore the long-term outcomes and safety of TCAs in this patient population.