Medical Health Encyclopedia

Skin Coolants. Ethyl chloride (Chloroethane) and fluori-methane are chemicals that cool the blood vessels in the skin. Sprays that contain these chemicals are not anesthetics, but are used to inactivate the sensitive areas. To use the spray, the patient must be in a comfortable position. The spray bottle is held upside-down, about 12 to 18 inches from the targeted area, and the face must be covered if the spray is being used near the head.

Tricyclic Antidepressants

Tricyclic antidepressants relieve pain in up to two-thirds of patients. These agents not only relieve depression, which can be common in PHN sufferers, but certain tricyclics specifically block sodium channels, which play a role in causing pain in PHN. Nortriptyline (Pamelor, Aventyl), amitriptyline (Elavil, Endep), and desipramine (Norpramin) are standard agents.

According to one study, two thirds of patients obtain pain relief if they take tricyclics within three months to a year after a herpes zoster attack. The agents are less successful when taken after that. It may take several weeks for the drugs to become fully effective, however. They are much less successful in patients who experience burning pain or allodynia (pain that occurs with normally non-painful stimulus, such as a light touch or wind).

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Unfortunately, tricyclics have side effects that are particularly severe in the elderly, who are also more likely to have PHN. Desipramine and nortriptyline have fewer side effects than amitriptyline and are preferred for older patients. Side effects include:

• Dry mouth.
• Blurred vision.
• Constipation.
• Dizziness.
• Difficulty in urinating.
• Disturbances in heart rhythm.
• An abrupt drop in blood pressure when standing up.

Anti-Seizure Drugs

Certain anti-seizure drugs have effects that block over-excitation of nerve cells and may be helpful for PHN patient.