Postherpetic neuralgia

What is postherpetic neuralgia?

Postherpetic neuralgia (PHN) is a nerve pain (neuralgia) that persists after the shingles rash has cleared. If the pain from shingles goes but then returns at a later date, this too is called PHN.

Shingles is caused by the chickenpox (varicella-zoster) virus. After a chickenpox infection, the virus lies dormant in one or more nerves in the body. This can later be reactivated (often after being unwell or when there has been some immunosuppression) and cause a typical rash. About 1 in 5 people have shingles at some time in their lives. Shingles is most common in people aged over 50 but can occur at any age, including in children. Many people with shingles have pain (although it is very common to have no pain or only very mild pain if shingles occurs under the age of 50) but the pain usually eases soon after the rash clears. Postherpetic neuralgia is pain that persists (or returns in some people) for longer. See the separate leaflet called Shingles (Herpes zoster) for more details.

Postherpetic neuralgia symptoms

• Pain. Postherpetic neuralgia causes pain on and around the area of the skin that was affected by the shingles rash. The pain is mild or moderate in most cases but can be severe in some cases.

• Pain characteristics. The pain is usually a constant burning or gnawing pain. There may also be sharp or stabbing pains that come and go. Some people only get the sharp stabbing pains without the burning sensation.

• Skin sensitivity. The affected area of skin is often very sensitive and hurts to touch. Even slight touch, such as the rubbing of clothes or a draught of air on the affected area, may cause pain and feel tender. There may also be itchiness (which can be significant) over the affected area.

• Sleep disorder. Many people find that their sleep is disturbed.

• Depression. Having this pain can lead to symptoms of depression occurring in some people.

Postherpetic neuralgia treatment

Postherpetic neuralgia is not like other pains, such as headaches or toothache. The pain is caused by the nerve endings which were affected by the shingles. These are inflamed or damaged by the infection. Because the pain is arising from the nerve endings, rather than the skin itself, normal painkillers are largely ineffective. Specific drugs may be required which act on the nerve endings themselves.

• General measures.

  • Loose-fitting cotton clothes are best to reduce irritation of the affected area of skin.

  • Pain may be eased by cooling the affected area with ice cubes (wrapped in a plastic bag or a tea towel), or by having a cool bath.

  • Some people find that putting several layers of 'cling film' over the affected area of skin helps. This allows clothes to slide over the skin without irritating.

• Commonly used traditional painkillers. Traditional painkillers such as paracetamol that can be bought over the counter are unlikely to ease postherpetic neuralgia in most cases.

• Tricyclic antidepressant medicines.

  • An antidepressant medicine in the tricyclic group is a common treatment for PHN. It is not being used here to treat depression but to act on the nerve endings. The dose is much lower than that used for depression.

  • Tricyclics ease nerve pain (neuralgia) very well. There are several tricyclics.

  • Amitriptyline is the one most commonly used for nerve pain. Pain is stopped, or greatly eased, in up to 8 in 10 cases of PHN treated with amitriptyline.

  • Nortriptyline is the other tricyclic that is sometimes used to treat PHN.

  • A tricyclic will usually ease the pain within a few days; however, it may take 2-3 weeks. It can take several weeks before you have maximum benefit so it is best to persevere for at least 4-6 weeks to see how well the tricyclic is working.

  • If a tricyclic works, it is usual to take it for a further month after the pain has gone or eased. After this, the dose is gradually reduced and then stopped. It should be re-started quickly if the pain returns.

  • Tricyclic antidepressants sometimes cause drowsiness. This often eases in time. To try to avoid drowsiness, a low dose is usually started at first and then built up gradually if needed. It is also usually taken at night.

  • A dry mouth is another common side-effect. Frequent sips of water may help with this.

• Anti-epilepsy medicines (anticonvulsants). An anti-epilepsy medicine is an alternative medication to try and reduce nerve pain.

  • Gabapentin is commonly tried to help manage postherpetic neuralgia.

  • An anti-epilepsy medicine, such as gabapentin or pregabalin, can stop nerve impulses causing pains separate to their action on preventing epileptic seizures.

  • As with tricyclic antidepressants, a low dose is usually started at first and built up gradually, if needed. It may take several weeks for maximum effect as the dose is gradually increased.

• Strong (opiate) painkillers.

  • These are the stronger traditional painkillers, for example codeine, morphine and related medicines. As a general rule, they are not used first-line for neuropathic pain. This is mainly because they are not very effective for neuropathic pain. The medicines listed above tend to work better for neuropathic pain.

  • There is a risk of problems with medication dependence, impaired mental functioning and other side-effects with the long-term use of opiates.

  • Tramadol is a painkiller that is similar to opiates but has a distinct method of action that is different to other opiate painkillers. It is sometimes used for postherpetic neuralgia but, again, does not work as well as anti-epilepsy medications.

• Combinations of medicines. Sometimes both a tricyclic and an anti-epilepsy medicine are taken if either alone does not work very well. As they work in different ways, they may complement each other and have an additive effect on easing pain.

• Lidocaine patches (topical lidocaine). Lidocaine is normally used as a local anaesthetic. Lidocaine patches contain a special gel allowing the active ingredient, lidocaine, to seep into your skin. The aim is for the lidocaine to block the pain signals coming from the nerve. Lidocaine patches are not usually advised as a 'first-line' treatment. However, they may be considered for people when other treatment options have not worked well, are unsuitable, or have caused bad side-effects. A patch is worn for 12 hours (day or night as you prefer) on or near the painful area and the skin left open to breathe for the other 12 hours. In some areas of the UK this is not able to be prescribed.

• Capsaicin cream. This is sometimes tried if the above treatments do not help, or cannot be used because of problems or side-effects. Capsaicin is thought to work by blocking nerves from sending pain messages. Capsaicin cream is applied 3-4 times a day. Hands should be washed immediately after applying it. It can cause an intense burning feeling when it is applied; this is particularly the case if it is used less than 3-4 times a day, or if it is applied just after taking a hot bath or shower. (However, this side-effect tends to ease off with regular use.) Capsaicin cream should not be applied to broken or inflamed skin. It is therefore not suitable for use during an episode of shingles. It should only be used on healthy skin which is painful due to PHN. In some areas of the UK this can only be prescribed by pain specialists.

• Treatment for itch. Some people have a severe itch with PHN. This is difficult to treat. An antihistamine taken at bedtime may improve sleep. It may also reduce scratching in the night (which may then also make the itch less severe the following day).

Side-effects and titrating dosages of medicines

For most of the medicines listed above, it is common practice to start at a low dose at first. This may be sufficient to ease the pain but the dose needs to be increased if the effect is not satisfactory. This is usually done gradually and is called titrating the dose. Any increase in dose may be started after a certain number of days or weeks - depending on the medicine. The doctor will advise as to how and when to increase the dose if required and also the maximum dose that can be taken for each particular medicine.

The aim is to find the lowest dose required to ease the pain. This is because the lower the dose, the less likely that side-effects will be troublesome. Possible side-effects vary for the different medicines used. A full list of possible side-effects can be found with information in the medicine packet. Some people don't have any side-effects and some people are only mildly troubled by side-effects that are OK to live with. However, the side effects for some people are difficult to live with and a switch to a different medicine may be an option if this occurs.

Common questions

How common is postherpetic neuralgia?

Postherpetic neuralgia is extremely unusual in people aged under 50 and, if it does occur, it tends to be mild.

Postherpetic neuralgia is both more likely to develop, and more likely to be severe, in people aged over 60.

Studies suggest that about 2 in 3 people over the age of 60 who have shingles develop postherpetic neuralgia and that this increases to about 3 in 4 people over the age of 75.

However, postherpetic neuralgia goes away quickly in the majority of people. Between 1 in 8 and 1 in 10 people still have pain after 1 month; 1 in 20 still have pain at 3 months. About 3 in 100 people still have some pain a year after their shingles infection.

Why does the pain persist in some people?

The symptoms of postherpetic neuralgia can last for several months in some people. Shingles causes inflammation of the nerve. Whilst the pain is understandable whilst the rash and inflammation is present, it is not clear why some people continue to have pain when the acute inflammation has gone. It is thought that some scar tissue or ongoing inflammation next to the nerve, or in the nearby part of the spinal cord, may be a factor. This may cause pain messages to be sent to the brain.

Will the pain go away?

Without treatment, PHN typically eases gradually and goes. Some people have a slow improvement over a long period of time. A very small number of people do not have any improvement over time without any treatment.

With treatment, most people will have some benefit and lots of people will have very good relief from the pain.

Can shingles and postherpetic neuralgia be prevented?

Shingles can only be prevented if people have never had chickenpox, or if they have very good immunity against the chickenpox virus (that is, against the varicella-zoster virus). Most people in the UK have chickenpox as a child. Immunity to the chickenpox virus reduces as you become older.

People who have been vaccinated against chickenpox can still get shingles but it is much less common than in people who had chickenpox infections. The chickenpox vaccine is not currently part of the NHS childhood vaccination schedule. It has been recommended that it is added to the routine schedule but it is not yet clear whether this will happen.

There is a vaccine against the varicella-zoster virus which is now offered routinely to people in the UK aged 70-79 years. The efficacy of the vaccine declines with age and so it is not recommended for people aged 80 years or older. This vaccine is the most effective way of preventing the development of postherpetic neuralgia by preventing shingles. It is a very effective and safe vaccine.