Rheumatoid arthritis is a chronic systemic disease of unknown aetiology. It is characterised by synovial fluid accumulation and by inflammation in the joints, tendons, ligaments, bone and soft tissues. Inflammation causes the release of multiple mediators, such as kinins, which induce a systemic response.

The inflammatory pain experienced is due to peripheral tissue injury, caused by damage induced by the mediators, concurrent infection or trauma. It is usually responsive to NSAIDs and opiates.

Rheumatoid arthritis can also cause nerve injury and produce neuropathic pain, which is less responsive to opiates.

Treatment aims in rheumatoid arthritis are:

• to halt the disease process

• to relieve symptoms, especially pain

• to improve functional and vocational capabilities

• to prevent deformity by joint protection and splintage

• to correct existing deformity using surgery.

This article will focus on the relief of pain and will relate to the following case study:
MANAGING PAIN IN RHEUMATOID ARTHRITIS

Pain should be assessed with respect to function, debility, sleep disturbance, chronicity and acute exacerbations. The type of pain should be classified as either nociceptive, neuropathic or a mixture of both. The possibility of infection exacerbating or causing the increase in pain should be considered.

Assessment of the patient's pain can be difficult due to cultural, social, demographic and environmental factors. The patient's current psychological state, previous history and the current physical pathology may also make assessment difficult.

If the pain is thought to be nociceptive, a trial of simple analgesia using the WHO ladder should be tried. Paracetamol and an NSAID can be useful in decreasing stiffness and reducing inflammation. If the patient is intolerant of standard NSAIDs because of gastric irritation then one of the Cox-2 inhibitors, such as rofecoxib (Vioxx) or celecoxib (Celebrex), may be helpful. As this patient is already on opiates the weaker opiates are unlikely to be helpful and may increase the likelihood of adverse reactions.

For patients without active infection and with localised pain a TENS machine may help. Those with more widespread pain may find acupuncture helpful, but the acupuncturist should avoid areas of oedema, effusion or inflammation. Physiotherapy may reduce pain and protect function.

Neuropathic pain, characterised by burning, shooting or throbbing sensations may respond to simple analgesia and opiates, but this is less likely due to underlying nerve damage and a reduction of opiate receptors at the dorsal horn within the spinal cord.

Drugs such as amitriptyline are useful for burning pains and in those patients who have disturbed sleep; 10 mg at night is a reasonable starting dose, particularly in the elderly.

If there is a shooting element to the pain then an anticonvulsant is often used. Gabapentin (Neurontin) is licensed for neuropathic pain and if tolerated can reduce shooting pains. It is not unusual to commence treatment with amitriptyline and add gabapentin.

This patient may benefit from a trial of amitriptyline and gabapentin before increasing her dosage of opiates.
Opiates and nonmalignant pain

There is disagreement about opiate use in chronic nonmalignant pain because of concerns about addiction, and the fact that not all pain is opiate responsive. Patients may also think that opiates signify a serious illness.

The use of opiates for nonmalignant pain is considered in provisional recomendations -- currently under review available from the Pain Society .

Opiates should only be considered after all other avenues of analgesia have been tried. There should be a careful history and examination and appropriate special investigations. Psychological and social issues and the patient's beliefs about their pain and what they expect from opiates should be explored. It is unlikely that opiates will relieve all of their pain. Medication that is partially effective should be continued (eg antidepressants and anticonvulsants).

Opiates should be avoided, or at least considered carefully if there is:

• a history of substance abuse

• a severe character disorder

• a chaotic home environment.

In these cases referral to a multidisciplinary pain service is sensible.

The primary outcome of opiate treatment is analgesia, with a secondary outcome of improved function. Figure 1 lists the key issues to consider when prescribing opiates.
Monitoring

Assess patients regularly for:

• analgesia

• functional change

• sleep

• mood

• side-effects

• signs of drug abuse -- such as early prescriptions, lost medication, documented intoxication, frequent missed appointments, use of other scheduled drugs.

Patients should be warned of the side-effects of opiate medication. These include constipation, nausea, vomiting, itching and somnolence. Anticipating these side-effects is advisable, with prescription of antiemetics and laxatives with the opiate.

Less common side-effects include respiratory depression, weight gain and hormonal effects (reduced adrenal function, reduced sexual function and infertility). Common side-effects occur in the first few days and should be treated appropriately. The less common side-effects may require a reduction in dosage or gradually stopping the opiate.

Opiate toxicity may result from accumulation of metabolites, particularly in patients with impaired renal function. Symptoms include drowsiness, confusion and the unpleasant sensation of seeing objects moving in the periphery of vision. Fentanyl, which is excreted via the liver, may be a suitable alternative in such patients.

Evidence of tolerance or addiction should prompt referral to a specialist service, eg a multidisciplinary pain service or drug addiction service.
CONCLUSION

The patient in this case study has pain secondary to her rheumatoid arthritis and has been given opiates. Her request for increased analgesia should be assessed and the cause of her pain determined.

Appropriate analgesia for nociceptive or neuropathic pain should be prescribed using simple analgesia, tricyclic antidepressants or anticonvulsants, before an increase in her opiate.

Alternative treatment such as TENS, acupuncture or physiotherapy may be useful. If this strategy fails then an increase in opiate may be useful but it should be done carefully.

Referral to a specialist multidisciplinary service is advisable if she continues to request opiate analgesia without improvement of pain or function.
THE PATIENT

• A 64-year-old woman has suffered from chronic rheumatoid arthritis for many years and has been prescribed small doses of morphine by another GP.

• She is now asking for increasing doses, as the original prescription is no longer effective.

• Opioids should be only one aspect of the patient's treatment

• A treatment plan should be discussed with the patient and expected goals and a time frame agreed

• Stress that improved analgesia, changes in physical, psychological and social function are the expected outcomes. Improved sleep and decreased anxiety are not sufficient to justify continued treatment

• Close liaison should be maintained between primary care and the specialist service

• A single doctor should prescribe the opiate, in most situations the GP is best placed to do this

• Sustained-release opioids by the oral or transdermal route reduce the risk of abuse

• Short-acting opioids can be used as rescue medication or during the titration phase in conjunction with the specialist service

• Drug dosage increases should occur at fixed intervals during the initial titration phase until analgesia or side-effects occur

• Avoid mixed agonist/antagonist drugs, eg pentazocine

• Avoid compound analgesia