PHN Treatment: Antidepressants

To treat neuralgia, specifically trigeminal and postherpetic neuralgia, physicians typically begin by prescribing antidepressants, anti-convulsants, or anti-spasticity drugs. Normally, antidepressants function by regulating levels of serotonin, dopamine, and norepinephrine in the brain to increase the sensitivity of nerve cells to glutamate, which is a non-essential amino acid linked to anxiety and depression, as well as the way one's body interprets pain; however, these medications are usually prescribed in smaller doses for neuralgia patients. Specifically, tricyclic antidepressants (which also affect nervous sodium channels) are usually prescribed to patients suffering from postherpetic neuralgia (PHN), rather than trigeminal or glossopharyngeal neuralgia.

These antidepressants should ease nerve pain within a few days, although they can also take up to several weeks to begin working fully, and are less effective in patients with burning pain or pain triggered by external stimuli. They are more effective when started within the first year after symptoms occur. Patients usually become dissatisfied with medication therapy, because it only moderates the pain and nerve pain can re-emerge unless dosage is increased over time (this is actually a phenomenon that has developed among patients suffering depression; no scientific correlation to neuralgia patients has been established). Side effects for tricyclic antidepressants include: dry mouth, constipation, bladder problems (especially in men with enlarged prostrate conditions), impaired sexual function, dizziness, drowsiness, blurred vision, increased heart rate, and weight gain. Unfortunately, side effects are more severe in the elderly- who are more at risk for neuralgia.

Nortriptyline (Pamelor, Aventyl), amitriptyline (Elavil, Endep), and desipramine (Norpramin) are standard drugs, but desipramine and nortriptyline have fewer side effects than amitriptyline and are preferred for older patients. In a study published in 2005 by the UCSF Pain Clinical Research Center, Michael Rowbotham treated postherpetic neuralgia patients with desipramine, amitriptyline, and fluoxetine. He concluded that: "Desipramine produced the greatest reduction in pain intensity (47%), followed by amitriptyline (38%) and fluoxetine" (Journal of Pain, Vol. 6, Issue 11). Additionally, he found that fluoxetine exhibited the most severe side effects: "The fluoxetine group had the highest noncompletion rate, with 1 subject hospitalized for hyponatremia. Although the magnitude of pain reduction and the category pain relief rating was not significantly different among the 3 drugs, the tricyclics desipramine and amitriptyline were well tolerated and provided clinically meaningful pain relief in 53% to 80% of subjects."


Antidepressants for neuralgia include:

- Amitriptyline: Elavil, Amitril, Emitrip, Endep, Etrafon, Levate, Limbitrol, Novotriptyn, Triavil. This is the most commonly used antidepressant for neuralgia treatment, and in most cases it does NOT demonstrate a loss of affectivity over time.

- Protriptyline: Vivactil

- Nortriptyline: Aventyl, Pamelor

- Desipramine: Norpramin

- Duloxetine: Cymbalta

- Fluoxetine: Prozac (US), Seronil, Fontex (Europe). The use of fluoxetine to treat neuralgia is more experimental, and often used only as an alternative to oter antidepressants, due to its higher cost.

Diagnosing Neuralgia

Neuralgia presents a conundrum to both doctors and patients, because of the difficulty inherent in diagnosing it. Although there are common symptoms for neuralgia, such as a constant, burning pain or a short, stabbing pain (both in localized areas), these are also symptoms which accompany a variety of other disorders. For example, people with trigeminal neuralgia are often diagnosed with having toothaches or even damage to the jawbone. This can be further complicated by the irregularity of the pain attacks; remission can last for months and typically there is no lasting paralysis, although episodes are sometimes precluded by a more lasting, throbbing sensation. In extremely rare cases, localized numbness and muscle spasms accompany the pain, which can be severe enough to also disrupt regular heartbeat rhythms.
Also involved in diagnosing neuralgia is pinpointing the nerve from which the pain is originating; unfortunately, this is difficult to do, and oftentimes the origin of the pain remains unknown. The mechanisms in the nervous system that are often actually attributed to neuralgia include: overly-sensitive neural receptors, malfunctions in the ion-transfer process along neural pathways, cross-signaling between large and small fibers, or damage in the central nervous system that "misreads" peripheral signals.

Introduction to Neuralgia

Neuralgia is characterized by a burning or stabbing pain that follows the path of a nerve. Because it usually occurs in conjunction with nerve damage or degeneration, it is most common in people over the age of 50 (and is more often diagnosed in women than men). Typically, it is classified by the type of nerve involved, the most common diagnosis being "trigeminal neuralgia," which involves intense pain on one side of the face. Although it can be a result of nerve damage or inflammation, the most common cause of trigeminal neuralgia is nerve compression (pressure- in this case from facial blood vessels- that inhibits normal neural pathways). Neuralgia can be a difficult condition to live with, not only due to the debilitating pain, but also because it can be triggered by the slightest external stimuli: such actions as brushing one's teeth or walking in a cool breeze can prompt intermittent bouts of stabbing pain that lasts anywhere from a few seconds to a few minutes at a time; sometimes, such episodes can be precluded by a prolonged throbbing sensation.
The easiest form of neuralgia to diagnose is postherpetic neuralgia, which exists in regions of shingles outbreak. Shingles (herpes zoster) arises when dormant chickenpox virus in nerve cells reactivates, causing pain, rash, and blisters. Although the skin usually heals within a month, sometimes pain persists and this is postherpetic neuralgia.
Two other recognized forms of neuralgia include occipital neuralgia and glossopharyngeal neuralgia. The first is pain in the neck, back of the head, or behind the ears resulting from damage, inflammation, or compression to the occipital nerves in the head. The latter, most rare form of neuralgia, is actually more common in men, and involves pain in the tonsils, tongue, or the back of the throat. Similar to the other cases of neuralgia, it is assumed that the pain results from compression of, or damage to, the glossopharyngeal nerve, although the exact cause is unknown.