Postherpetic neuralgia

Postherpetic neuralgia has a significant negative impact on the quality of life and the functional status of patients who develop affective disorders in the form of anxiety, depression, as well as disturbances in social activity, sleep, appetite. Accounting for all these factors is very important in the therapy of patients with postherpetic neuralgia.

After suffering varicella, the Herpes zoster virus remains in the body in a latent state, localizing primarily in the sensory ganglia of the spinal nerves and the trigeminal nerve. When reactivated, the virus causes the formation of a characteristic vesicular rash and the appearance of pain in the innervation zone of the corresponding nerve root.

[1], [2], [3], [4], [5], [6], [7], [8]

Symptoms of postherpetic neuralgia

In 50% of patients, the rash is localized on the trunk, 20% - on the head, 15% - on the hands, and 15% - on the legs. After a few days the rash is transformed into a pustule, then it forms crusts and disappears by the end of the 3-4th week. Nevertheless, in many patients, after the disappearance of the rash in the area of the affected dermatome, pain persists for several months and even years. This pathological condition is called postherpetic neuralgia (PHN). Especially often, herpetic neuralgia develops in patients over the age of 60 (50%). Pain is associated with inflammatory changes in the ganglia of the posterior roots of the spinal cord and peripheral nerves (leading pathophysiological mechanisms are ectopic activity, expression of sodium channels on nerve cell membranes, and central sensitization).

In patients with postherpetic neuralgia, there are 3 types of pain: permanent, deep, blunt, pressing or burning; spontaneous, periodic, stitching or shooting ("electric shock") and allodic (acute, superficial, burning, usually occurring with a light touch).

In most patients, pain associated with postherpetic neuralgia decreases within 1 year. Nevertheless, in some patients it can persist for years and even for the rest of life.

Treatment of postherpetic neuralgia

In terms of treatment of postherpetic neuralgia, the timely treatment of herpes in an acute period with the help of antiviral agents (acyclovir, famciclovir and valaciclovir) plays an important role. Studies have shown that all 3 of these drugs reduce the pain associated with herpes zoster, and the risk of postherpetic neuralgia. For symptomatic pain therapy associated with postherpetic neuralgia, antidepressants, local anesthetics and anticonvulsants are used.

• Most often used tricyclic antidepressants (amitriptyline in a dose of up to 150 mg / day). Given the predominantly elderly age of patients with postherpetic neuralgia in the appointment of tricyclic antidepressants, it is important to strictly consider their side effects.
• Several randomized trials have shown the effectiveness of lidocaine plates. The transdermal delivery of a local anesthetic directly into the area of pain localization allows to effectively stop the pain syndrome. Unlike drugs used for local analgesia in the form of ointments or gel, this dosage form has an undeniable advantage in the convenience of use (the plate is easily pasted to the place of pain, does not stain clothes, etc.). In addition, the plates protect the pain zone from external stimuli (touching clothes, etc.), which is very important, since most patients have allodynia. Unwanted adverse reactions in the form of skin reactions (itching and redness of the skin) usually spontaneously disappear within a few hours after cessation of treatment. Another local drug, capsaicin, is currently used rarely, since at the beginning of the treatment it usually intensifies the pain due to the activation of nociceptive A5 and C-fibers (anesthesia occurs later due to desensitization of nociceptors in the peripheral terminals of the sensory nerves).
• Of anticonvulsants in the treatment of postherpetic neuralgia, gabapentin and pregabalin proved to be the most effective. Gabapentin is prescribed in a dose of 300 mg on day 1, 600 mg (in 2 divided doses) on day 2, and 900 mg (3 times a day) on day 3. If necessary, increase the dose to 1800-3600 mg / day (in 3 doses). The recommended dose of pregabalin is 75 to 150 mg twice daily or 50 to 100 mg 3 times a day (150-300 mg / day). In the absence of a satisfactory effect, after 2-4 weeks of treatment, the dose is increased to 600 mg / day.