Mild, moderate and severe pain

Mild to moderate pain

The majority of patients presenting to the doctor or pharmacist have mild to moderate pain. This pain usually results from headache, migraine, arthritis, angina, ulcers, trauma, back pain, earache etc. With such pains, management is based upon use of minor analgesics such as paracetamol and NSAIDs. For pains in the mouth and throat, local anaesthetic preparations are often used.

Moderate to severe pain

Moderate to severe pain can be a major medical problem. It is more difficult to alleviate than mild-moderate pain. Those drugs that are available tend to have more serious adverse effects than the simple analgesics used for milder pain.

Types of severe pain

Moderate to severe pain falls into a number of well-recognised groups.

Post-operative pain

Pain may be a major problem even after relatively trivial operations and the patient's experience of post-operative pain is often not related to the extent of surgery. Post- operative pain may have important cost implications when it delays the discharge of patients from hospital.

Moderate to severe pain

Acute trauma

Traumatic pain such as that due to contusions and, especially, fractures, can be very severe. As with post-operative pain, the severity may be unrelated to the seriousness of the injury.

Non-malignant pain

Arthritic pain and chronic back pain come into this category. The pain of rheumatoid arthritis can be particularly problematic because, unlike the pain of osteoarthritis, it is not relieved by rest or change of posture.

Malignant pain

Cancer pain is in a separate category to other kinds of severe pain. Its origins are somewhat obscure: it may be due to expansion of the tumour within a confined space causing pressure on nociceptors, to inflammatory changes, or to biochemical substances released by the tumour. Biochemical changes, which occur as a result of the cancer (eg. high blood calcium in bone cancer), may exacerbate the pain by altering the threshold of nociceptors. However, similar sized tumours in similar locations may cause extreme pain in one patient, yet only mild or no pain in another.

Neurological pain

This is pain due to pressure on, or damage to, nerves. Sciatica and pain after shingles (post-herpetic pain) are in this category. Although the conditions themselves are often chronic, the pain is usually an intense sharp pain, more like acute pain.

Treatment of moderate/severe pain

Moderate to severe pain is treated with the more potent NSAIDs, with opiates or with combinations of the two.

Opiates

The opiates, or narcotic analgesics, relieve pain by acting on specific receptors in the central nervous system (CNS). These are part of the body's own pain-regulating system involving the enkephalins and the endorphins. They fall into two main groups:

• the weaker narcotics include codeine, dihydrocodeine, pentazocine and dextro-propoxyphene which are of moderate potency and which have a lower potential for addiction than the potent opiates. These drugs are often preferred in chronic but non-life threatening pain states.
• the strong narcotics such as morphine, diamorphine, phenazocine and methadone are used in the severest pain, but have a high potential for dependence. Buprenorphine (Temgesic) has less potential for dependence. The differences between the opiates are thought to be due to their differing activity on various CNS opiate receptor types.
  

Opiates are the drugs of choice for severe, acute or life threatening pain states where the risk of dependence is not a significant issue.

Combinations

NSAIDs

Some of the more potent NSAIDs seem to be effective in certain severe pain states. They include ketorolac (Toradol), promoted for post-surgical pain, and fenoprofen (Fenopron), for moderate to severe pain states.

Combinations

Combinations of an opiate with a NSAID are often additive especially in cancer pain. Other drugs often used in combination with analgesics for moderate to severe pain include:

• antihistamines - promote drowsiness and reduce inflammation
• muscle relaxants - used in combinations for musculo-skeletal pain
• anxiolytics - used to reduce the 'anxiety' component contributing to pain, to promote sleep and also for their muscle relaxant properties
• some types of severe pain and psycho-genic pain states are 'opiate insensitive'. These conditions may be treated with psychotropic drugs such as antidepressants or anticonvulsants