Potent opioids and chronic pain

It was said earlier that chronic pathological pain can become an independent disease with serious consequences for many organs and systems. Pathological pain loses its protective functions, it has a maladaptive and pathological significance for the body. Insurmountable, severe, pathological pain causes mental and emotional disorders, disintegration of the central nervous system, frequent suicidal actions, structural and functional changes and damage in internal organs and the cardiovascular system, dystrophic tissue changes, disruption of vegetative functions and the endocrine system, secondary immune deficiency. There is a large arsenal of non-narcotic analgesics for the treatment of chronic pain. But in those situations where their use is limited by the occurrence of side effects (gastro, nephro- and hepatotoxicity) or their analgesic potential is exhausted, the question arises about the possibility of using strong opioid analgesics for the treatment of chronic non-oncological pain. Doctors recognized that from a legal and ethical point of view, patients with chronic pain cannot be denied opioid analgesics that provide maximum pain relief; opioids began to be used to treat pain in rheumatoid arthritis, back pain, and neuropathic pain.

Prescribing opioid (narcotic) analgesics for non-oncological pain is possible only when doctors have high theoretical training and serious clinical experience in treating chronic pain syndromes. The doctor must be able to clearly determine the nature and cause of pain, consider and use the entire arsenal of drug and non-drug treatment methods for a specific patient, including surgical ones.

Opioid analgesics are the main treatment for somatogenic pain syndromes of moderate and high intensity in various fields of medicine. In terms of analgesic effect, they significantly exceed all known non-opioid analgesics. Opioid analgesics have a central mechanism of action, which is realized by interacting with opioid receptors in different parts of the central nervous system.

The class of modern opioid analgesics includes drugs with different analgesic activity and a different spectrum of other additional properties, which is of great importance for the correct choice of opioid in specific clinical situations. Differences in properties of different opioids are due to their different relationships with opioid receptors:

1. affinity for a certain type of receptor (mu-; kappa-; sigma-receptors),
2. the degree of binding to the receptor (strength and duration of the effect),
3. competitive ability (antagonism) to a certain type of receptor.

Accordingly, opioids can be agonists or stagonists of certain receptors, which determines the spectrum of properties inherent to each opioid.

Opioids of different groups differ in the degree of expression of such specific properties as the ability to cause tolerance and dependence.

Tolerance, i.e. resistance to opioid analgesia, is associated with the “habituation” of receptors to the dose of opioid used and a decrease in the analgesic effect during long-term therapy (for morphine, tolerance begins to appear after 2-3 weeks), which requires a gradual increase in the analgesic dose of the opioid.

Drug dependence (physical and/or mental) can develop at different times from the start of therapy. Physical dependence manifests itself when drug use is suddenly stopped, with a characteristic withdrawal syndrome (psychomotor agitation, chills, abdominal cramps, nausea, vomiting, salivation, etc.) and requires special therapy. Mental dependence (addiction or drug addiction) is characterized by an irresistible psychological need to obtain the drug (even in the absence of pain) to avoid severe emotional experiences and severe discomfort when stopping drug use.

To identify the risk of developing drug addiction, you can use the CAGE and CAGE-AID questionnaires. The differences are that the first questionnaire is designed to identify the risk of alcohol addiction, while the second one has questions to identify drug addiction.

Question	Yes	No
Have you ever wanted (in general or in the last 3 months) to reduce your intake of alcohol or medications?
Have people around you made comments (in general or in the last 3 months) about your use of alcohol or drugs?
Have you ever felt guilty about using alcohol or drugs?
Have you ever had a drink or taken medication first thing in the morning to calm your nerves or cure a hangover (in general or in the last 3 months)?

The ability to cause dependence (the so-called narcotic potential) is expressed differently in opioids of different groups. Some opioids (gramal, butorphanol, nalbuphine), due to minimal narcotic potential, are not classified as narcotic drugs and are non-narcotic analgesics. Mu-receptor agonists (except tramadol) have a greater ability to cause dependence. Due to the high social significance of this dangerous property of opioid analgesics, all countries have a special system of control over the use of narcotic drugs to prevent possible abuse. Differences between different opioids in narcotic potential determine the features of their accounting, prescription, dispensing, and use.

To minimize the risk of developing psychological dependence when using opioids in patients with chronic pain, preliminary selection and systematic monitoring of the use of recommended doses of narcotic analgesics is required.

Most opioids are metabolized in the liver and their metabolites are excreted by the kidneys, so the effect of opioids may be enhanced in patients with impaired function of these parenchymal organs and may manifest as CNS depression (sedation, respiratory depression).

Contraindications to the use of all opioid analgesics are: hypersensitivity (intolerance) to a specific drug, intoxication with alcohol or drugs that depress the central nervous system (hypnotics, narcotics, psychotropic drugs), concomitant use of MAO inhibitors and a period of 2 weeks after their withdrawal, severe liver or kidney failure, epilepsy, drug withdrawal syndrome, pregnancy and breastfeeding. Caution is required when prescribing opioids to elderly and senile patients (the safe analgesic dose may be 1.5-2 times lower than in middle-aged people.

Recently, transdermal therapeutic systems (TTS) for the dosed administration of drugs (estrogens, androgens, lidocaine) have been increasingly introduced into practical medicine.

TTS allows the patient to administer the drug independently without the services of medical personnel; the procedure is non-invasive, which undoubtedly contributes to greater patient compliance with treatment.

Prescription of all narcotic analgesics should be carried out only in case of ineffectiveness or intolerance of previously conducted etiopathogenic therapy and low risk of developing addiction, knowledge of the doctor of all the features of the prescribed drug, drug interactions, complications.

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