What is the Type of Pain? An introduction

What is the Type of Pain? An introduction

Dr Dominic Aldington, Consultant in Pain Management

When considering medication for pain the first step is probably to determine what type of pain is present; that is, what is the underlying mechanism for the pain. If the pain could have a neuropathic component then the options are probably different to those where it is thought to be solely nociceptive. The difficulty is that traditionally neuropathic pain was considered a relatively rare event while the modern concept is that it is probably far more common than initially thought.

Nociceptive Pain

Nociceptive pain is defined as “An actually or potentially tissue-damaging event transduced and encoded by nociceptors.” Nociceptors in turn can be considered to be the endings of nerves that are stimulated by damage to normal tissue. Thus nociceptive pain is pain associated with damage to normal tissue.

The traditional starting point for nociceptive pain has become the Acute Pain Ladder. This suggests that the initial agent should be paracetamol, and if this is not sufficient then the next step up on the ladder is taken where an NSAID or weak opioid is introduced into the mix. However, the usual point is to add to the paracetamol and not to replace it. If this is not sufficient to control the pain then a strong opioid should be introduced, either as well as or instead of the weak opioid. The aim is then to climb down the ladder as the pain recedes – rather than jumping from the top rung to the ground!

Figure 1. Acute Pain Ladder

The use of opioids for the management of chronic pain has now come under a cloud for a number of very important reasons. One of these is over concerns about the side effects of long term opioids, although another reason is because it is unclear how helpful opioids are in helping management of long term pains; to date there is no good evidence that they are helpful for most people. As a result, escalation to opioid use should be not undertaken lightly and should be closely monitored. A very useful resource, for both patients and healthcare professionals, to support the prescribing of opioids is Opioids Aware: www.rcoa.ac.uk/faculty-of-pain-medicine/opioids-aware.

Neuropathic Pain

Neuropathic pain is defined as “pain caused by a lesion or disease of the somatosensory nervous system”. It is a clinical description and not a diagnosis.

As with nociceptive pain, it may be possible to consider a similar “ladder” scheme for neuropathic pain. One can consider starting with a tricyclic antidepressant. If this is insufficient, add in an anticonvulsant, or appropriate serotonin and noradrenaline uptake inhibitor. If these do not help, then specialist support, as found in a pain clinic, should be sought. For symptoms of allodynia topical agents can be of benefit.

Nociplastic Pain

Nociplastic pain is a relatively new concept and is defined as “Pain that arises from altered nociception despite no clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors or evidence for disease or lesion of the somatosensory system causing the pain”. It can be found in combination with nociceptive pain.

March 2019, M-C-UK-02-19-0001