ANTINEURITICS: WHAT ARE THEY FOR, HOW THEY WORK, EFFECTS - MEDICINE - 2024

The antineuríticos are a group of drugs of different nature but with a common purpose: to avoid or reduce neural inflammation. Depending on their origin, they can act directly on the affected peripheral nerves or have effects on the central nervous system.

Most of these drugs were not initially intended as antineuritics. Although most have actions at the neurological level, their therapeutic use was intended for other pathologies, such as seizures, depression, degenerative diseases or chronic pain.

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In the case of drugs that act at the level of the nervous system, the side effects due to their administration are abundant. In fact, their use as antineuritic drugs was an occasional finding, initially described as an adverse event. Some of these effects can be severe and require discontinuation of treatment.

What are they for?

Antineuritic drugs are administered to reduce inflammation and therefore the symptoms of peripheral neuropathies. To better understand this task, it must be clear what these neuropathies commonly known as neuritis consist of.

Neuritis

Inflammation of a peripheral nerve or one of its branches is known as neuritis. This condition can be caused by local or generalized trauma, various infections, nutritional disorders, poisoning, neurodegenerative diseases, cancer or even unknown causes.

The term neuritis is also used, erroneously, to describe any painful dysfunction of a peripheral nerve even in the absence of inflammation. In this case the correct word is neuralgia, although this concept is only limited to pain and does not consider the other consequences of neuropathies.

Neuritis doesn't just manifest itself with pain. In fact, the initial symptoms are changes in the sensitivity of the area innervated by the affected nerve root and a tingling sensation. If the causative medical condition is perpetuated, there is usually muscle hypotrophy, alterations in tissue function and local skin changes.

Everyday uses

Antineuritic treatment covers a significant number of neurological pathologies. Neuritis can occur in practically any peripheral nerve in the body, but there are certain particular cases that deserve mention.

Intercostal neuritis

It is the inflammation of the nerves that run between one rib and another. The signs and symptoms associated with this particular type of neuritis are very varied.

In severe cases, just breathing can be painful. Other common actions are also annoying like laughing, sneezing, coughing, sighing, or stretching your arms.

Trigeminal neuralgia

It occurs due to inflammation of one of the highest cranial nerves: the trigeminal nerve. Its area of ​​innervation is the face, therefore the symptoms are located in this region.

It is usually unilateral so it only affects one half of the face and causes peculiar grimaces to reduce discomfort. The pain is stabbing or stabbing and very intense.

Optic neuritis

One of the most common causes of acute visual loss is optic neuritis. Unilateral or bilateral inflammation of this cranial nerve affects young people and is more common in women. In addition to partial or total loss of vision, there is difficulty distinguishing colors and pain when moving the eyeball.

Vestibular neuritis

The vestibular nerve innervates the inner ear and fulfills fundamental functions in balance. Hence, its inflammation is characterized by dizziness, nausea, vertigo, imbalance and even fainting. In these cases, hearing is not compromised and there is almost no pain.

How do antineuritics work?

Antineuritics are drugs produced for a different task that also demonstrated the ability to alleviate the symptoms of neuritis.

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Among these drugs, the most important are:

Antiepileptic drugs

Gabapentin and pregabalin are the main representatives of this group. Originally devised as seizure treatments, they now play a vital role as neuropathic, antimigraine, and antidepressant treatments.

Its mechanism of action as antineuritics is not well known. At the central level it is known that they act on the receptors of the neurotransmitter GABA, helping to prevent seizures, but at the peripheral level their function is not clear. Some authors believe that it is due to its effect on voltage-gated calcium channels in pain pathways.

Carbamazepine and oxcarbazepine are widely used in trigeminal neuralgia, showing encouraging results. Lamotrigine, another new generation antiepileptic drug, acts on sodium channels and inhibits the release of glutamate, a powerful neurotransmitter that is very active in the genesis of pain.

Antidepressants

Serotonin / norepinephrine reuptake inhibitors and tricyclic antidepressants may be helpful as antineuritics. Like antiepileptic drugs, these drugs have effects on the central and peripheral nervous system. Its use has been used almost exclusively for chronic neuralgia.

These drugs activate the descending nerve pathways dependent on norepinephrine and serotonin. When this pathway is stimulated at the level of the spinal cord, the neuronal feedback is not fulfilled, limiting the pain signals that ascend to the brain through the opposing nerve bundles.

Opioids

Morphine, methadone, and meperidine are widely used opioid drugs in neuritis. Its intention is only to reduce pain, although a certain central effect may prevent the mental disorders that often accompany these neuropathies. Its mechanism of action involves the central as well as the peripheral nervous system.

Opioid receptors are found throughout the body. Depending on the drug used and the dose, they may have local or distant actions. His task focuses on NMDA antagonism, a very important neurotransmitter in the activation of pain. Thanks to this phenomenon the analgesic effect occurs.

Other antineuritics

Local anesthetics are useful due to their localized action and few systemic effects. Lidocaine, bupivacaine and mepivacaine are used in injection, gel or patches, blocking local nerves and therefore inhibiting the painful stimulus for the duration of their action.

Some neuritis is caused by vitamin deficiency, therefore compounds with vitamin B are widely used in these cases. Medications composed of elements of the Vitamin B complex are especially useful in intercostal neuritis.

The administration of cannabinoid derivatives for the treatment of certain chronic neuropathies has now been allowed. While their use remains controversial, some studies support the relief they provide thanks to the action of THC centrally.

Side effects

The vast majority of antineuritic treatments have central undesirable effects. Most antiepileptic and antidepressant drugs cause drowsiness, dizziness, unsteady gait, and blurred vision.

The presence of nightmares and eating disorders also occur with the consumption of these medications.

Another common side event is addiction. This is also the case with opioids and cannabinoids. The feeling of well-being and sometimes of euphoria that they produce can end up being a vice. Caution and proper dosage are necessary in these patients.

References

1. Hoorbakht, Hedieh and Bagherkashi, Farid (2012). Optic Neuritis, its Differential Diagnosis and Management. The Open Ophthalmology Journal, 6: 65-72.
2. Baron, R; Binder A. and Wasner, G. (2010). Neuropathic pain: diagnosis, pathophysiological mechanisms, and treatment. The Lancet. Neurology, 9 (8): 807-819.
3. Hsu, Eric S. et al. (2013). Intercostal neuralgia. Problem-Based Pain Management, Chapter 5, 114-119.
4. Jeong, S. H; Kim, HJ and Kim JS (2013). Vestibular Neuritis. Seminars in Neurology, 33 (3): 185-194.
5. Cruccu, Giorgio and collaborators (2016). Trigeminal neuralgia: new classification and diagnostic grading for practice and research. Neurology, 87 (2): 220-228.
6. Ang, CD et al. (2008). Vitamin B for treating disorders of the peripheral nerves. Recovered from: cochrane.org
7. Lee, G. et al. (2018). Medical Cannabis for Neuropathic Pain. Current Pain and Headache Reports, 22 (1): 8.
8. Wikipedia (last edition 2018). Neuropathic pain. Recovered from: es.wikipedia.org