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Salbutamol belongs to the group of drugs that stimulate the Beta-2 receptor. These drugs are used mainly in the treatment of respiratory diseases, while there are cases of the use of beta-2-agonists in gynecology and obstetrics.

Effects of salbutamol

Salbutamol is a beta-adrenergic stimulant and it is aselective beta-2 agonist . Most of these receptors are found in the respiratory system, hence their wide application in pulmonology.

These receptors in the respiratory tract are found, among others, on the surface:

  • epithelial cells,
  • smooth muscle cells,
  • mast cells,
  • endothelial cells,
  • type II pneumocytes,
  • submucosa glands,
  • cells of the cholinergic ganglia.

Their stimulation causes a multidirectional reaction that allows the patient to stabilize the breathing. The agonist effect of salbutamol on beta-2 receptors causes:

  • relaxation of the central and peripheral bronchi,
  • intensification of ion transport within the epithelium,
  • secretion of bronchodilator by epithelial cells,
  • mucous cells increase their secretory activity,
  • ciliary movement is accelerated, as a result of these reactions the bronchi are cleansed faster and more effectively,
  • blood vessels in the bronchi dilate,
  • the epithelium becomes less permeable, which reduces plasma leakage in the lungs.

All the above-mentioned reactions give the patient relief during an attack of dyspnea.

Salbutamol is one of the short-acting beta-2-agonists. This is due to the hydrophilic nature of its molecule. This drug passes directly from the aqueous extracellular space to the core of the beta-2-adrenergic receptor. Thanks to this, the effect of salbutamol is noticeable after just a few minutes.

The drug reaches its maximum effect after about 30 minutes , and the full effect of salbutamol lasts up to about 4 hours. After this time, the ionic bond between the drug molecule and the active site of the receptor is broken and the substance is removed from the cell by diffusion.

Drugs from this group can be used as an adjunct to glucocorticoid therapy(it is observed in the case of asthma therapy) or as drugs used chronically. The most desirable forms are:

  • inhalation spray suspension,
  • inhalation powder or nebulization solution, i.e. puffs.

By such administration of the drug, the risk of systemic side effects is reduced, the drug quickly reaches the desired site of action and reaches a high concentration there without the risk of prior hepatic metabolism or poor absorption from the gastrointestinal tract.

In the discussed group of drugs, doctors observe the phenomenon of tachyphylaxis. This situation is somewhat similar to the phenomenon of tolerance, but here the decrease in drug efficacy by a decrease in effectiveness is due to the exhaustion of mediators in the presynaptic membrane of neurons. Most often this happens when the patient is trying to deliver multiple doses in quick succession.

The first dose has an effect because the neurotransmitters that are triggered by the drug's mechanism of action in the nervous system are thrown into the synaptic cleft and passed on to the next neuron.

Subsequent doses deplete the supply of neurotransmitters in the synapse, which reduces the effect of the dose. Again, contrary to the phenomenon of tolerance, increasing the dose will not cause the drug to work again.

The desired therapeutic effect will be achieved after some time, during which the synthesis of new neurotransmitters will take place. It has been noted that in asthmatics, the "rapid onset of tolerance" to beta-2-agonists is genetically determined.

In some patients, regular use of short-acting beta-2-agonists leads to a decrease in bronchodilator response. In this situation, the patient should not decide to increase the dose of the drug on his own, and should immediately contact the attending physician.

Indications for the use of salbutamol

Symptomatic treatment of reversible bronchial obstruction in the course of bronchial asthma and chronic obstructive pulmonary disease (COPD). Salbutamol can be used to treat chronic bronchitis and emphysema.

In asthma, short-acting beta-2-agonists (SABAs) are administered primarily to terminate an asthma attack at the lowest dose that is effective. Asthma exacerbates when the patient is ineffective or exposed to a triggering factor.

During an asthma attack, it becomes difficult to breathe, the patient becomes nervous, and may even panic. The person is often leaning against various objects to facilitate breathing.

Often the patient is unable tosay a full sentence on the exhalation or even one word, so it is very important that the environment in which the patient is staying knows how to help him in the event of an attack if the patient is not able to react appropriately. The patient should also have information that he / she suffers from asthma.

Contrary to the treatment of asthma, COPD treatment involves the chronic use of beta-2-agonists. Constant therapy with bronchodilators is aimed at reducing the likelihood of exacerbations of this progressive disease. It is not recommended to stop the therapy, even if the patient feels a great improvement after taking the medications.

Treatment of category A patients (with a low risk of exacerbation and mild disease symptoms) involves the use of inhaled short-acting beta-2-agonists mainly in the case of dyspnea, while in more advanced forms of COPD bronchodilators are regularly used, both short-acting and and long-acting forms.

Although salbutamol also has a relaxant effect on the muscles of the uterus, which can be used to stop labor during preterm labor, it is not the drug of choice. The drugs more often used in this situation are nifedipine and atosiban.

Salbutamol dosage

Suspension in the form of an inhalation aerosol :

Dosage is usually determined individually with the patient by a pulmonologist who takes into account the advancement of the disease.

Adults and children over 12 years of age usually take 1-2 inhalations to relieve attacks of breathlessness. For this group, the maximum dose is 8 inhalations a day. Experts remind you to use inhalation 10-15 minutes before the dyspnea trigger in the event of exercise in an asthmatic or allergen exposure. In children under 12 years of age, the usual dose to relieve an attack of breathlessness is 1 inhalation.

Incorrect use of the inhaler may reduce the dose that enters the respiratory system, which reduces the therapeutic effect of the drug. The doctor or nurse should instruct the patient exactly how to use the inhaler.

If, during an attack of breathlessness, a child or an elderly person has a problem to use the inhaler correctly, inhalation chambers are available on the market, which make it easier for the patient to take the right dose of the drug without the need to coordinate inhalation with administration of the drug.

Although nebulizations are currently an alternative to administering the drug through an inhalation chamber, they are not recommended for parents to treat a chronic child. Much betterthey work well in treating an attack of dyspnea, when the child needs to be given an increased dose of the drug, and the child is distracted and cooperation with him may prove to be a challenge for the caregiver.

Salbutamol nebuliser solutiondosed as follows: 2.5 mg salbutamol 3 to 4 times a day in nebulisation (this dosage applies to adults and children from 2 years of age) life).

Salbutamol is also available in the form of tablets andsyrup. Oral forms of this drug are less popular because they do not work as fast as the so-called puffs and cause more side effects.Tablets can be given to children from 6 years of age and adults , whilesyrup can be taken by children from 2 years of age .

Tablet dosing starts with 2 to 4 mg, up to two to four times a day. For children from 6 to 12 years of age, dosage should be limited to 2 mg three to four times a day.

For syrup, the dosage is as follows :

  • children from 2 to 6 years of age: 2.5 to 5 ml of syrup three to four times a day,
  • children aged 6 to 12: 5 ml of syrup three to four times a day,
  • adults and adolescents over 12 years of age: 10 ml of syrup three to four times a day.

Salbutamol is also available as an injection solutionwhich can be administered subcutaneously, intramuscularly or intravenously.

Contraindications to the use of salbutamol

The drug must not be taken by people who are hypersensitive to salbutamolor other excipients present in a given form of the drug. In the safety data sheet, hypersensitivity to sympathomimetic amines is also mentioned as a contraindication to the use of salbutamol.

Salbutamol should not be taken in any form to prevent a threatening miscarriage.

Myocardial infarction is also mentioned as a contraindication to the use of this drug.

Precautions and interactions

Literature emphasizes thatthe use of beta-2-agonists is not recommended as monotherapy in patients with severe and unstable asthma . These patients should take bronchodilators in addition to glucocorticoid therapy. They should be under the constant supervision of the attending physician and have regular pulmonary function tests, as uncontrolled asthma may lead to the death of the patient during a severe attack of breathlessness.

A very important piece of information for the physician is when the patient has to increase the number of doses taken in order to obtain relief duringbreathlessness. This may indicate that asthma control has deteriorated and treatment of this patient should be reviewed.

Taking the drug should be done exactly as explained by the attending physician during the visit. Do not change the dosage of the drug or the form of administration on your own.

If a patient experiences paradoxical bronchospasm following administration of a beta-2-agonist, discontinue use of the drug and institute an alternative treatment.

You should not take salbutamol with propranolol, as they have opposite effects and drug interactions may occur and the effectiveness of therapy may be reduced.

The drug should be used with caution in patients with metabolic disorders, such as diabetes or hyperthyroidism. Salbutamol increases blood glucose levels, which makes it difficult to control diabetes in patients. Glucocorticosteroids used in polytherapy with salbutamol also negatively affect the patient's glycaemia.

The drug should be administered with caution to patients with concomitant phaeochromocytoma, vascular diseases resulting in narrowing of the vessel lumen, and hypertension.

In rare cases, salbutamol can cause myocardial ischemia. The risk is mainly in patients with underlying heart disease and in elderly patients. If the treated person feels sudden pressure and pain in the chest and shortness of breath, they should see a doctor immediately.

Treatment with beta-2-agonists creates a risk of hypokalemia, i.e. lowering the serum potassium concentration. Drugs that accompany beta-2-agonists in polytherapy, such as glucocorticosteroids, also cause a decrease in potassium levels in the body. During therapy with these drugs, serum potassium levels should be monitored by means of laboratory tests, and in the event of its decrease, potassium supplementation in the patient should be considered.

You may develop narrow-angle glaucoma with salbutamol. In patients who are already diagnosed with or suspected glaucoma, exercise caution and instruct the patient to prevent medication from entering the eye.

Do not use salbutamol with monoamine oxidase inhibitors and tricyclic antidepressants.

Salbutamol and pregnancy and breastfeeding

The patient should not be given salbutamolduring pregnancy unless absolutely necessary. This drug is included in the safety category C of drugs in pregnancy. In animals, it has been observed that the administration of high doses of salbutamol causes fetal harm.

Nursing womenbreastfeeding patients should wean the baby from the breast during treatment with salbutamol . It has not been proven in studies that this drug has a negative effect on the newborn baby. Salbutamol can make driving and the use of machines difficult because its side effects include trembling of the muscles of e.g. the hands and dizziness.

Side effects of salbutamol

Very common side effects include skeletal muscle tremors .

Common side effects include:

  • headaches,
  • tachycardia,
  • palpitations,
  • muscle spasms.

You can meet less often:

  • hypersensitivity reaction,
  • hypokalaemia (where therapy in combination with other drugs that reduce plasma potassium levels increases the risk of hypokalaemia),
  • hyperactivity,
  • dilatation of peripheral blood vessels,
  • muscle stiffness,
  • heart rhythm disturbance,
  • ischemic heart disease.

When taking the drug by inhalation, the throat and oral mucosa may be irritated. Paradoxical bronchospasm may also occur, which manifests itself in wheezing immediately after taking the drug.

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