Many acute and chronic diseases of the musculoskeletal system are accompanied by the appearance of persistent spasms of skeletal muscles. This enhances the existing pain syndrome and may contribute to the consolidation of the pathological positions of the affected areas of the body. Also, cramped muscles become tight and sometimes squeeze nearby neurovascular bundles. Therefore, the treatment of many diseases includes muscle relaxants, allowing to cope with muscle spasms.
How muscle relaxants work
After the recommendations of the doctor about taking muscle relaxants, people often wonder what it is. Usually, by mistake, people begin to take antispasmodics and become frustrated without getting the desired effect.
These are two different groups of drugs.
Muscle relaxants act on the striated musculature, which is designed to maintain body position and perform voluntary and automated movements. It is also called skeletal because such muscles are attached to bones. But antispasmodics act mainly on smooth muscle fibers, which are located in the walls of blood vessels and hollow internal organs. Therefore, the testimony of these funds is different.
The mechanism of action classifies muscle relaxants. They are central and peripheral, and it depends on the area of application of the molecules of the active substance. Each group includes drugs of different molecular structure, which determines the characteristics of their use.
Peripheral preparations are depolarizing, non-depolarizing and mixed. They have a curare-like effect, affecting neuromuscular transmission at the level of synapses with acetylcholine receptors.
Non-depolarizing drugs have a competitive effect on acetylcholine, and they are also called anti-depolarizing. Due to the content of nitrogen atoms, peripheral muscle relaxants are water-soluble and practically do not penetrate through the blood-brain barrier. The action of digestive enzymes destroys them. Therefore they can only be administered parenterally. The preparations for this group are powerful enough. Consequently, it is necessary to strictly observe the dosage and control the function of the respiratory muscles in the background of their use.
Central muscle relaxants act at the level of the central nervous system. They affect the formation of excitatory impulses in certain motor areas of the brain and some parts of the spinal cord. The stability of their molecules and pharmacodynamic features allow using many of these drugs in the form of tablets and solutions for parenteral administration. They are often prescribed for various diseases of the spine and other pathologies of the musculoskeletal system, including outpatient treatment.
Muscle relaxants of central action are included in the anesthesia protocol for various surgical interventions since their introduction facilitates tracheal intubation and allows temporarily blocking the work of the respiratory muscles, if necessary, mechanical ventilation (artificial respiration). They are also used in traumatology during reposition of displaced fragments at fracture for the relaxation of large muscle groups. Some remedies are used for the relief of resistant convulsive syndrome and a modern version of electroconvulsive therapy.
Peripheral muscle relaxants have much more widespread use, which is explained not only by the simplicity of their use but also by a higher safety profile.
The most common situations in which drugs are prescribed in this group are:
• muscular-tonic syndrome of vertebral origin (with osteochondrosis, spondylosis, sciatica and other radiculopathies of various etiologies);
• pronounced myofascial syndrome, including those supported by psychosomatic and neurotic causes, chronic stress;
• chronic pain syndrome of different origin, often due to the presence of muscle spasms;
• in the presence of central paralysis (after a stroke, with multiple sclerosis, cerebral palsy).
Speaking more simply, central muscle relaxants are quite often prescribed for local or back pain in the limb in the back and neck, for spastic paralysis. And in the presence of muscle tension in the cervical region, an indication for these drugs may be the appearance of vertebral artery syndrome.
The use of muscle relaxants is limited by the presence of renal and hepatic failure, myasthenia and myasthenic syndrome, Parkinson’s disease, peptic ulcer, hypersensitivity to the drug.
Epilepsy and convulsive disorder of a different etiology are contraindications for prescribing this group of drugs. But for intractable seizures that threaten cardiac arrest, the doctor may decide to introduce muscle relaxants with simultaneous transfer of the patient to a ventilator. At the same time, the use of muscle relaxant is not a way to combat cramps, and it only allows to reduce the spasm of the upper respiratory tract and respiratory muscles, to achieve controlled breathing.
Pregnant and lactating women should not use muscle relaxants. Such drugs are prescribed only with the ineffectiveness of other methods of treatment if the potential benefit to the mother is higher than the risk of developing complications in the child.
Side Effects and Overdose
Against the background of the use of muscle relaxants, the following side effects may appear:
• headache, dizziness;
• general weakness;
• nausea, discomfort in the stomach;
• dry mouth;
• the decrease in blood pressure (mainly when using drugs of peripheral action);
• skin rash;
• anaphylactic shock;
• the weakness of the muscles of the face, neck and respiratory muscles (intercostal muscles and diaphragm) – with the use of peripheral muscle relaxants.
Non-compliance with the recommendations of the doctor and the unauthorized excess of the permissible dose is fraught with the development of an overdose, which can be life-threatening. But pronounced side effects may develop against the background of the average therapeutic dose of the drug. When using peripheral muscle relaxants, this may be due to acetylcholine deficiency due to natural features or the use of other medications.
Alcohol, psychotropic drugs, and drugs that affect the metabolic rate of drugs in the liver strengthen the effect of muscle relaxants.
The overdose of muscle relaxants requires emergency care. Since the risk of respiratory arrest is high due to inhibition of the respiratory muscles, the patient is tried to be hospitalized in the intensive care unit. If anti-depolarizing drugs were used, protein or other anticholinesterase agents are injected into the treatment regimen. There are no antidotes to other muscle relaxants; therefore, in all other cases, blood purification methods, mechanical ventilation, and symptomatic therapy are used.
Use of muscle relaxants for back pain
In the medical literature, some studies are proving the effectiveness of muscle relaxants in the treatment of acute pain in the neck and back for a short period (up to one – two weeks). Muscle relaxants can contribute to the recovery of the patient by blocking pain.
Typically, muscle relaxants are used in the following cases:
In cases of muscle spasms
Muscle cramps occur when a muscle (or muscle group) suddenly shrinks, causing severe pain. When this happens in the back or neck, it is often caused by lifting a heavy object or a sharp turn of the body, resulting in muscle strain. Muscle relaxants in such cases are prescribed along with painkillers to relieve cramps.
When providing emergency care to physicians, it is essential to determine if a severe problem causes pain in the back or neck. If the depression is not associated with harsh conditions, such as an unstable fracture or a tumor, the patient may be prescribed muscle relaxants and pain medications for a short time to treat painful stretching of muscles, ligaments or tendons.
After spinal surgery
Muscle relaxants are often prescribed after surgery, even when the pain has subsided. In some cases, muscle spasms can appear in those parts of the body that are located quite far from the area of operation. Muscle relaxants are often given in hospitals and prescribed to patients in the first days and weeks after discharge. Prescribing physicians and instructions attached to medications must be carefully followed. It is useful to discuss in advance how to take the drugs: on a schedule to prevent the appearance of pain, or only when they are needed. A separate rather than simultaneous intake of painkillers and muscle relaxants can help, since in this case some drug will always affect the body and the pain will not become too loud when the effect of the drug ends.
Muscle relaxants can also be prescribed when a patient starts a new physiotherapy program. Taking muscle relaxants can improve patient mobility, reduce anxiety associated with the need to exercise, and reduce the likelihood of exacerbations of pain from muscle spasms.
Muscle relaxants can help temporarily relieve back pain. Some studies indicate that taking analgesics in combination with muscle relaxants is more effective than taking only painkillers.
Doubts of doctors in the effectiveness of the use of muscle relaxants
Even though muscle relaxants are prescribed very often, the validity of their use in the medical community is questioned.
The increasing frequency of prescribing these drugs raises questions about the abuse, side effects, and limited evidence of their effectiveness, especially when taken regularly to treat chronic pain in the neck and back.
The results of research on muscle relaxants are ambiguous. Some studies and analyses have found that muscle relaxants are more effective than placebo for non-specific acute back pain in the short term.
However, the results of other studies show that patients who applied for emergency medical care for back pain did not experience any additional positive effects from taking muscle relaxants.