Naloxone: uses and side effects of this drug

This drug is used to treat some cases of opioid drug overdose.

Naloxone is an opioid antagonist used to treat opiate used to treat opioid intoxication or overdose (especially heroin). It is also indicated to treat respiratory depression or CNS (Central Nervous System) depression.

In this article we will learn about its characteristics, routes of administration, mechanism of action, adverse reactions, indications and precautions to be taken regarding its use.

Naloxone: characteristics

Naloxone is an opioid antagonist drug, which is indicated to treat opioid intoxications. to treat opioid intoxication and respiratory depression.. The fact that it is an opioid antagonist means that it "slows down" or blocks the effect of this substance. It is generally administered as an injectable solution.

The main contraindication to naloxone is hypersensitivity to it, or hypersensitivity to its main compound, naloxone hydrochloride (or to any of its excipients).or hypersensitivity to its main compound, naloxone hydrochloride (or to any of its excipients).

Opioids

To understand how naloxone works, it is also useful to know what an opioid is.

Opioids are substances that reduce pain, i.e. analgesic substances. They are natural substances (from seeds called "poppy seeds"), but they can also be synthesized, they can be used as pharmaceuticals or as drugs (depending on their use, characteristics,...). Morphine, heroin, hydrocodone, codeine, etc. are opiates. These molecules act by binding to opioid receptors (a type of protein), minimizing the person's perception of pain..

Routes of administration

Continuing with naloxone, it is usually administered intravenously (IV) through an injectable solution.. It can also be administered intramuscularly (IM), or it can be administered through an intravenous infusion. This last, less well-known route of administration consists of introducing an intravenous solution into the bloodstream on a continuous basis; it is performed by means of a catheter inserted into a peripheral or central vein.

However, it is important to note that in acute cases (especially in cases of overdose of opiates such as heroin), the most recommended route of administration is intravenous (IV), since the effect is produced more quickly; specifically, the effect becomes evident after approximately 2 minutes. The duration of the effects will always depend on the dose.However, it is generally between 1 and 4 hours.

If a second or third dose is needed, this will always depend on the opioid to be antagonized (or the type of respiratory or CNS depression that the patient presents); specifically, the type of opioid, its amount and the route of administration used, among others.

Mechanism of action

Naloxone is actually is composed of naloxone hydrochloride, which is a semi-synthetic derivative of morphine (a natural opiate). (a naturally occurring opioid). Its mechanism of action involves specifically antagonizing opioids; specifically it acts by competing at opioid receptors.

This drug has a very high affinity for these types of receptors (i.e., it fits very well with them). What it does thanks to this is to displace opioid antagonists and agonists.

Composition and dosage

At the chemical level, it is derived from oxymorphone, a very potent semi-synthetic opioid analgesic.. The drug is composed of naloxone hydrochloride. Specifically, each 1 ml ampoule of naloxone contains 0.4 mg of naloxone hydrochloride.

The recommended doses in adults, generally, are 0.4 to 20 mg through the intravenous route. In the event that no improvement in respiratory depression is obtained after administration by this route, it can be administered again at intervals of 2 to 3 minutes (always by a medical professional). Of course, its use must be indicated and prescribed by a physician..

Indications

Naloxone is often known for its use during acute intoxication or opioid overdose.. The main natural opiate is morphine. Another opiate drug is heroin, a drug synthesized from morphine.

Other indications for naloxone are: to treat respiratory depression or CNS (Central Nervous System) depression. The respiratory depression mentioned above is usually caused by the consumption of opiates, either natural or synthetic. It is also indicated for babies who have just been born, with mothers who have been taking opiates.

Another interesting fact is that when naloxone is administered in cases of opiate dependence, the following happens symptoms of physical dependence to it increase..

Pharmacokinetic properties

Pharmacokinetics has to do with the absorption time of the drugs, the duration of their effect, etc. In other words, it encompasses the processes through which the drug passes once it is administered in the organism. Naloxone (naloxone hydrochloride) is rapidly absorbed by the gastrointestinal tract..

But why is naloxone not usually administered orally? It is also effective, but to produce the same effect as from the other routes, much higher doses would be necessary to allow an antagonism of opiates (in case of overdose). This is why it is administered intravenously and intramuscularly.

Precautions

Special caution should be taken with patients who have a physical dependence to narcotics (narcotics are analgesic and/or anesthetic drugs), or who have been intoxicated by this type of substances; this is because the use of naloxone can induce an acute withdrawal syndrome.. On the other hand, naloxone is not effective when respiratory depression is due to factors other than opioids.

Naloxone should also be used with caution in elderly patients, especially in those with previous Cardiovascular disease.. This is because there are known cases where naloxone has caused serious cardiovascular adverse effects in the elderly.

In addition, it is not recommended to take naloxone at high doses during surgery after consuming opioids. Special care or caution should be exercised in patients with cardiovascular disease, or in patients taking cardiotoxic drugs that may cause heart disturbances.

Pregnancy and lactation

If you are pregnant, the risk/benefit ratio of taking naloxone should be assessed in consultation with your family doctor or doctor of medicine. in consultation with the family doctor or psychiatrist. There is not much data regarding the use of naloxone during pregnancy, but it is known that it can cause withdrawal symptoms in the baby.

Regarding breastfeeding, it is not known whether or not naloxone can pass into breast milk. It has also not been established whether infants who are breastfed have effects of naloxone.

Side effects

Like any drug, naloxone can also cause a number of adverse reactions in the patient, such as: nausea, vomiting, tachycardia, hypo/hypertension, headache, postoperative pain and fainting, among others.among others.

Other adverse reactions that can be caused by naloxone, and which have been reported especially in postoperative periods, are hypotension, hypertension, pulmonary edema, fibrillation and ventricular tachycardia. In addition, these adverse reactions have been seen mostly in people with cardiovascular disease or who have been taking similar drugs.

Bibliographic references:

• Ferrandis, V. (2013). Professional association of physiotherapists of Castilla y León. Pharmacokinetics and pharmacodynamics. Course of Pharmacology for Physiotherapists.
• Gregorio Marañón University Hospital. (2014). Continuous intravenous perfusion. Nursing documentation: 2 - 10.
• Ministry of Health, Social Policy and Equality. (2018) Fact sheet: naloxone. 1 - 8.
• Stahl, S.M. (2002). Essential psychopharmacology. Neuroscientific bases and clinical applications. Barcelona: Ariel.
• Vademecum. (2016). Naloxone.