Analgesics, make pain go to chronic pain?

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Pain is a fundamental feeling of survival and the most common reason people seek medical attention.

However, the pain that requires people to seek medical attention is often acute pain, and when acute pain develops into chronic pain, it becomes another medical condition . The World Health Organization put forward the concept of "chronic pain is a kind of disease" in 2000. Statistics show that more than 30% of the world's people have experienced chronic pain, resulting in a huge economic burden.

As a disease, chronic pain has attracted great attention from all over the world. The World Pain Congress recognized pain as the "fifth most vital sign of human beings" after respiration, pulse, body temperature and blood pressure. However, for a long time, people's understanding of chronic pain is still relatively one-sided. In order to prevent acute pain, people often choose quick-acting analgesic and anti-inflammatory drugs, but as everyone knows, such anti-inflammatory drugs bring the occurrence of chronic pain .

From pain to chronic pain

Unlike acute pain, chronic pain is considered to be pain that persists or recurs for more than 3 months.

If the point of acute pain is that it limits or stops our behavior, it prevents further injury and promotes wound healing to prevent similar injuries in the future. Then, chronic pain is an important disease that affects people's health problems and quality of life insignificantly.

The Lancet study revealed that chronic pain was associated with lower life expectancy even after controlling for higher rates of depression, suicide and opioid use.

Numerous studies have shown that when we do not treat the underlying pain cause, or because we cannot effectively relieve pain and the pain becomes chronic, there are some maladaptive changes in the nervous system that increase the intensity of the pain. When the pain becomes stronger, the body's thoughts and emotions will be negatively affected, and eventually the symptoms of depression will appear .

Specifically, if pain goes untreated for more than three months, it can leave a mark in the brain that permanently alters the body's pain signals, and intensified pain experiences increase the risk of pain becoming chronic. The pain time is less than half a year and can still be understood and tolerated by the patient, and if it exceeds this time limit, there may be more significant negative emotional changes . So, pain isn't just a "physical thing," even if it's just pain from a physical injury in the first place.

In addition, patients with chronic pain have also been found to have a certain relationship with depression and anxiety, but it is difficult to determine the cause and effect. Chronic pain and depression and anxiety interact repeatedly to form a vicious circle of pain-depression-anxiety-more pain . Pain increases unpleasant emotions and promotes the recall of unpleasant events, which in turn aggravate unpleasant emotions, thereby aggravating pain.

Faced with pain, tolerance is the choice of more people. Fan Bifa, director of the pain department of Beijing China-Japan Hospital, estimates that there are 80 million chronic pain patients in China . In one survey, about half of 2,779 patients over the age of 65 had daily pain, while 21.6% were not receiving any pain medication or other pain relief. And that doesn't include chronic ailments that aren't "painful" like ringing in the ears, itching, shortness of breath, etc.

Being taught to "bear hardships and stand hard work" since childhood, and "endure it for a while" when suffering from illness is the norm for many Chinese. But the truth is that the destructive power of pain is not necessarily attached to other diseases. Pain itself is destructive.

If a person bears pain for a long time, his tolerance to pain will become lower and lower, simple pain will become complicated, and treatable pain will become intractable . For example, in some clinical patients, it hurts to jump at the slightest touch. This is peripheral sensitization (primary hyperalgesia), which means that after long-term pain tolerance, the nervous system changes, turning simple pain into neuropathy.

Another type of hyperalgesia refers to the fact that the threshold of the anti-pain system will be lowered after a long period of pain tolerance . The lower the threshold, the stronger the perception of pain. As a result, when the pain threshold approaches "0". Even a normal feeling can be perceived by the body as a pain.

Chronic pain is placing a huge burden on individuals and the economy. Take the US data as an example. In 2010, the US medical system spent US$560 billion on chronic pain treatment alone, and the productivity loss caused by chronic pain was as high as US$635 billion.

Painkillers prolong pain?

Treating pain with anti-inflammatory drugs has long been standard medical practice. In the United States, 36 million people use over-the-counter pain relievers every day, and more than 111 million prescriptions for nonsteroidal anti-inflammatory drugs (NSAIDs) are dispensed each year.

For example, ibuprofen is a commonly used non-steroidal anti-inflammatory drug (NSAID), which is a non-selective cyclooxygenase blocker . Synthesize, produce analgesic and anti-inflammatory effects; play an antipyretic effect by acting on the hypothalamus thermoregulatory center.

Clinically, ibuprofen is mainly used to relieve symptoms of rheumatoid arthritis, rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, etc. It can also be used for soft tissue injury, low back pain, dysmenorrhea, and oral and eye operations. pain afterward. Currently, more than 20 million prescriptions for ibuprofen are prescribed each year in the United States.

But now, a new study suggests that these drugs may cause pain to last longer. Scientists at McGill University in Canada found that using anti-inflammatory drugs to relieve pain in the early stages of pain increases the risk of developing chronic pain later. Not only will this overturn past practice standards for treating pain with anti-inflammatory drugs, it will even rewrite pain management guidelines.

The occurrence of chronic inflammation is inseparable from the interaction between the nervous system and the immune system. Immune cells in the circulation are recruited to the damaged tissue site/inflammation site, releasing various inflammatory mediators, chemokines, lipids and proteases, acting on peripheral Nerves that regulate pain perception. Based on this, scientists believe that immune cells also play a role in the transformation of acute pain into chronic pain .

The researchers first studied 98 patients with low back pain to explore why patients had different disease outcomes three months after an acute low back pain attack -- some patients experienced pain relief after three months, while others developed chronic low back pain. Low back pain.

The researchers collected the peripheral blood of the patients during the acute pain period (t0) and at the follow-up 3 months later (t1), and analyzed and compared the changes of immune cells in the peripheral blood of the pain reliever and the pain persister. The results showed that the proportion of neutrophils in the peripheral blood of patients with pain relief gradually decreased over time, while the proportion of neutrophils in patients who developed chronic pain was almost no throughout the course of the disease. change .

Furthermore, neutrophils dominate the early stages of inflammation and provide the conditions for repair of tissue damage. During the acute pain stage, all patients with low back pain showed neutrophil activation and inflammatory response activation, but the intensity of inflammatory response in patients with pain relief was 75% higher in the early stage than in patients with persistent pain. Clearly, inflammation plays a key role in pain relief.

Based on this, the researchers blocked the neutrophils in mice in the experiment, prolonging the pain time to ten times the normal time. At the same time, the researchers also used anti-inflammatory drugs and steroids such as dexamethasone and diclofenac to treat pain, with the same results, although they were effective for pain early on.

Through a series of rigorous animal experiments, researchers can finally determine: whether acute pain turns into chronic pain depends on the intensity of the early inflammatory response, and the use of anti-inflammatory analgesics to suppress the inflammatory response at this stage will lead to prolonged pain duration .

The findings are also supported by a separate analysis of 500,000 people in the UK, which showed that those who took anti-inflammatory drugs for pain were more likely to experience pain two to ten years later, an effect that increased after taking paracetamol Not seen in people taking aminophenols or antidepressants.

rethink pain

Perhaps, we need to rethink pain, and how we treat it.

On the one hand, chronic pain should not be ignored . A survey involving 440,000 people in the United States shows that more than 20% of adults have chronic pain, regardless of age, gender, race, education level and income, the prevalence rate has increased, among which people with poor economic conditions suffer from chronic pain. Disease rates are rising fastest. According to the Global Burden of Disease Study, pain and related diseases are the leading cause of disability worldwide and affect life expectancy.

But at the same time, what does not match the pain caused by pain is that in the face of chronic pain, most people would rather endure the pain than seek medical treatment. In fact, it is precisely because chronic pain will bring endless physical pain or discomfort, psychological isolation and inferiority, which promote each other and form an inescapable circle, so chronic pain should get more attention .

Fortunately, there are many new areas that are opening up. For example, "pain departments" have been opened in many hospitals. All kinds of neuralgia, shoulder, neck, waist, and leg pain, cancer pain, as well as rheumatoid arthritis, post-herpetic sequelae, gout and other pain problems that are difficult to solve in other departments can be found in the pain department. Rehabilitation departments, chronic disease management departments, and psychiatry departments also provide relevant medical support.

On the other hand, while painkillers or anti-inflammatory drugs of all kinds can relieve our acute pain, in the final analysis, pain is not a disease or injury itself, it is a symptom of a disease or physical injury . Think about pain and think about ways to treat acute pain rather than just compromising pain with painkillers.

In fact, there are many types of commonly used pain relievers, including acetaminophen pain relievers, non-steroidal anti-inflammatory drugs (aspirin, ibuprofen, indomethacin, paracetamol, phenylbutazone, rofecoxib, celecoxib) ) and central pain relievers with severe side effects, such as opioids such as morphine and delhexidine. But the so-called medicine is three-point poison, and painkillers are no exception. All kinds of painkillers have their own specific toxic and side effects. Moreover, although taking painkillers can temporarily relieve pain, it also hides the location and nature of the pain, which is often not conducive to doctors' observation of the disease and judging the diseased part, and it is even more unfavorable for doctors to correctly diagnose and treat in a timely manner.

Previous research from the University of Waterloo has realised that anyone who is taking a diuretic and a renin-angiotensin system (RSA) inhibitor for high blood pressure (hypertension) should be cautious about taking the pain reliever ibuprofen at the same time. The researchers used computer-simulated drug trials to simulate the interaction of the three drugs and their effects on the kidneys. It was found that, in people with certain medical characteristics, the combination led to acute kidney injury, which in some cases could be permanent.

Chronic pain is real, it deserves to be treated with more caution, and chronic pain also gives us a good opportunity to recognize pain.