Generality
Pain therapy (also called analgesic therapy or pain medicine) aims to recognize, assess and treat chronic pain in the most appropriate manner.
The type of drug to be used may vary depending on the origin, nature and intensity of the painful stimulus to be treated. Therefore, before illustrating the categories of drugs most used in this area, it is useful to understand what chronic pain is and what causes it can trigger it.
Causes of chronic pain
According to the definition provided by the International Association for the Study of Pain (IASP), pain represents "an unpleasant sensory and emotional experience associated with tissue damage, actual or potential, or described in terms of damage. It is an individual experience and subjective, which converge purely sensory components (nociception), related to the transfer of the pain stimulus from the periphery to the central structures, and experiential and affective components, which modulate in an important and perceived way ".
Basically, three different types of pain can be distinguished: acute, chronic and procedural.
Chronic pain, the target of analgesic therapy, persists over time, is highly debilitating and is capable of causing not only physical, but also psychological, social and economic damages to the patients who are afflicted by it. For this reason, chronic pain is considered a real pathology.
Very often, chronic pain is believed to be a peculiarity of neoplastic diseases . However, tumors are not the only possible cause that can trigger the aforementioned form of pain. In fact, the cause may not be oncological, but may be, for example, of a neuropathic type, or associated with degenerative diseases of various kinds.
Drugs used
The choice of the type of drug to be used in pain therapy depends above all on the intensity and the type of pain that afflicts the patient.
The main classes of drugs used in pain therapy will be briefly described below.
NSAIDs
NSAIDs (non-steroidal anti-inflammatory drugs) are used in pain therapy when the latter is mild or moderate.
Generally, these medicinal products complement the analgesic activity with an anti-inflammatory and antipyretic action.
Their mechanism of action involves the inhibition of the cyclooxygenase enzyme, with consequent inhibition of prostaglandin synthesis responsible for mediating pain responses and inflammatory processes.
Among the active ingredients mostly used in pain therapy, we mention ketoprofen, diclofenac, naproxen and nimesulide.
To get more information about the properties and the mechanism of action of NSAIDs, we recommend reading the dedicated articles "NSAIDs: History, Mechanism of Action, Indications" and "NSAIDs: Side Effects and Contraindications".
Opioid analgesics
Opioid analgesics, widely used in pain therapy, are particularly indicated when the pain stimulus is moderate to severe.
These drugs exert their antinociceptive action through the stimulation of opioid receptors present in the whole of our body. In fact, these particular receptors are located on the pain pathways and their task is precisely to mediate and transmit painful stimuli.
Among the opioid analgesics mostly used in pain therapy we find codeine, tramadol, buprenorphine, fentanyl, oxycodone, methadone, hydromorphone and morphine.
Although they can be used in the treatment of pain of various origins and nature, the aforementioned active ingredients are considered as the most important drugs in the treatment of chronic oncological pain .
However, to get more information about the characteristics of this class of drugs, see the article on "Opioid drugs".
Antidepressants
Despite their main therapeutic indication is the treatment of depression, some active ingredients belonging to the classes of tricyclic antidepressants (or TCA) and serotonin and norepinephrine reuptake inhibitors (or NSRIs) have proved very useful in neuropathic pain therapy and can be used either alone or in combination with opioid analgesics.
Among the most used TCAs in this field, we mention amitriptyline and clomipramine.
Among the NSRIs, however, we recall duloxetine, an active ingredient that has proved particularly effective in the treatment of diabetic neuropathic pain.
Anticonvulsants
Some types of anticonvulsant drugs have also been found to be quite effective in treating neuropathic pain. In particular, gabapentin and pregabalin are among the active ingredients most used in this area.
These drugs, in fact, through the interaction with the voltage-dependent calcium channels present at the level of the central nervous system, are able to reduce the release of neurotransmitters involved in the modulation and transmission of the pain stimulus, such as substance P and peptide related to the calcitonin gene.
Local anesthetics
Among the local anesthetics mostly used in chronic pain therapy we find lidocaine.
More in detail, lidocaine is able to reduce and block the transmission of painful stimulus through the inhibition of voltage-dependent sodium channels present on cell membranes.
Non-pharmacological therapy
To the classical pain therapy performed with medicinal specialties, it is possible to combine a non-pharmacological pain therapy.
Of course, the type of approach that you decide to take varies according to the type of chronic pain that needs to be treated.
These different approaches include radiotherapy, cryotherapy, thermotherapy, massages and physiotherapy.
Finally, it is now known that the psychological component also plays a certain role in the perception and possible worsening of chronic pain. For this reason, in some cases, approaches based on behavioral or cognitive psychological techniques can be useful, as can the use of relaxation and imagination techniques and distraction techniques.
