The list of expectorant drugs that can be used for asthma is quite
extensive, but there are only a few truly effective ones: 1) acetylcysteine
(commercial names – acetylcysteine, ACC, mucomist , etc.); 2) mesna , or
mercaptoethanesulfonate ( mistabron ); 3) Bromhexine ( Bizolvon , Bromhexine,
Solvin , etc.); 4) ambroxol ( ambroxol , ambrosan , lazolvan , etc.); 5)
carboxymethylcysteine ( carbocysteine , mucodin , mucopront , etc.); 6) iodine
preparations (potassium iodide and mixtures based on it); 7) alkaline mixtures
based on sodium bicarbonate (soda).
The mechanisms of action of modern expectorants are mainly associated with an
improvement in the rheological properties of sputum – a decrease in viscosity,
elasticity and adhesion, as well as a decrease in the amount of mucus formed.
Drugs that normalize rheological characteristics are represented by: 1)
mucolytics (substances that thin mucus), 2) secretion rehydrators (increasing
the water content in it), and 3) agents that reduce adhesion (sticking) of
sputum to the bronchial wall.
Mucolytics act directly on bronchial mucus: if a small amount of medication is
added to a portion of viscous sputum, it will turn into a cloudy and completely
non-viscous liquid in a few minutes. The group of mucolytics includes two
classes of chemical compounds: proteolytic enzymes and thiols .
Trypsin, chymotrypsin and analogues containing them can be mentioned among the
first ones. The mucolytic effect of enzymes is associated with the cleavage of
peptide (protein) bonds of mucus glycoprotein molecules. In the 50s-70s. they
were used quite widely, but it soon became clear that proteolytic enzymes
contribute to the development of emphysema and pneumosclerosis. Therefore, they
cannot be prescribed for chronic lung diseases, the progression of which can
lead to emphysema and pneumosclerosis. Asthma is one of these diseases. In
addition, there are other mucolytics – thiols – no less effective and
absolutely safe.
Unlike proteolytic enzymes, thiols (acetylcysteine and mesna ) thin sputum by
breaking the disulfide “bridges” that bind glycoprotein molecules.
The mechanism of this reaction is quite simple, but the effectiveness of such
an impact is unusually high: sputum liquefies almost instantly. Therefore,
thiols are also used in otorhinolaryngology to clear viscous mucus from the
upper respiratory tract. By the way, other thiol derivatives (for example, the
domestic drug unitiol ) can also be effectively used as mucolytic agents. Most
thiols are used in the form of tablets or syrups, injections and inhalations.
When thiols are used orally, they are absorbed from the digestive tract into
the blood, secreted through the wall of the bronchus, thinning and exfoliating,
first of all, the parietal layer of mucus. And this significantly increases the
effectiveness of the expectorant action. That is, when thiols are taken orally
(as well as when injected), they act EXTRABRONCHIALLY, getting into the lumen
of the bronchus through its wall from the blood. When inhaled, thiols act
ENDOBRONCHIALLY, as they enter directly into the lumen of the respiratory
tract. Therefore, if there is a lot of mucus in the lungs, the drug does not
affect the parietal layer of the secret, which does not allow for the most
effective expectorant effect. In such cases, it is better to combine the use of
thiols inside with inhalations.
The scientific literature describes many cases where the use of thiols , in
particular acetylcysteine, causes bronchospasm with suffocation. However, prior
inhalation of a bronchodilator prevents it. Contraindications for the use of
thiols inside are severe chronic diseases of the digestive system: thinning of
the mucus eliminates its protective effect, which can lead, for example, to an
exacerbation of peptic ulcer and other ailments. In such cases, these agents
are recommended to be used in smaller doses and mainly in the form of
inhalations.
The extrabronchial mechanism of action is also inherent in another class of
substances – iodine salts, which are used in the form of mixtures and very
rarely in the form of solutions for intravenous administration. Being absorbed
into the blood, they are then secreted through the wall of the bronchus into
its lumen and, by virtue of the laws of osmosis, increase the water content in
the mucus ( rehydrate it), facilitating coughing. An unpleasant property of
these drugs is irritation of the skin and mucous membranes, since it is through
them that iodine salts are secreted. This is sometimes manifested by a rash and
itching, exacerbation of chronic inflammation of the mucous membranes in
various organs, which naturally limits their use. A positive property of drugs
containing iodine salts is a fairly pronounced antifungal effect. Therefore,
one of the additional indications for the appointment of iodine mixtures is the
development of candidiasis during treatment with inhaled steroids.
Alkaline solutions, in particular sodium bicarbonate (sodium bicarbonate),
which are used mainly in the form of inhalations, also have a mucus rehydrating
effect. Recommendations such as “plentiful alkaline drinking”,
declared as expectorant therapy, are rather doubtful. It can be added to the
above that, depending on the concentration, soda solutions also cause alkaline hydrolysis
of mucus, which increases the efficiency of expectoration. Thus, the
expectorant action of saline solutions is based on the rehydration of bronchial
mucus, that is, an increase in water in it. This reduces its adhesion
(sticking) to the wall of the bronchus, and according to some reports, it also
reduces the viscosity.
Another class of pharmacological substances that reduce sputum adhesion is
represented by bromhexine and its derivative, ambroxol . Bromhexine is a
substance of natural origin: for the first time it was isolated from a plant.
Subsequently, its chemical synthesis was carried out, and it became widely used
in pulmonology. To date, Bromhexine and Ambroxol are the most effective and
safe expectorants. They are usually used in the form of tablets and mixtures.
The main mechanism of action of bromhexine and its analogues is the stimulation
of the production of special substances in the lungs – surfactants with high
surface activity (similar to synthetic detergents). Therefore, rising up from
the alveoli (where they are produced), surfactants “wash” the mucus
from the bronchial wall. Preparations of the bromhexine group not only have an
effective expectorant effect, but also, when taken for a long time (over 3
months), contribute to the normalization of secretion, reducing the amount of
mucus formed in the respiratory tract. Long-term treatment with bromhexine at a
dose of 48 to 96 mg per day for 3-6 months, especially in the autumn-spring
periods, improves not only bronchial drainage, but also gradually normalizes
secretion, sometimes to almost complete absence of sputum. In the indicated
doses, these drugs are absolutely harmless. And according to the data available
in the literature, patients who regularly take lazolvan or bromhexine suffer
exacerbations of the disease twice as rarely.
The most complete cleansing of the respiratory tract from excess mucus (which
impairs bronchial patency and reduces the effectiveness of inhaled
anti-inflammatory and antiallergic drugs) can also be achieved by reducing its
amount in the lungs. For this purpose, drugs are used that affect its
production by mucus-forming cells and glands. These drugs include S-
carboxymethylcysteine ( carboxycysteine , or carbocysteine ), produced under
various commercial names. It is usually given in capsules or as a syrup. An
unpleasant side effect of carboxycysteine is its ability to exacerbate chronic
diseases of the digestive tract. Therefore, it cannot be used for a long time.
And in conclusion, I would like to warn doctors against a very common mistake:
TRY NOT TO PRESCRIBE PATIENTS WITH ASTHMA DRUGS THAT SUPPRESS THE COUGH (AS SO
MUCH HAPPENS), ESPECIALLY THE CODEINE SERIES. Such an action will only disrupt
bronchial drainage, aggravate bronchial obstruction and ultimately worsen the
patient’s condition. The same applies to drugs of the non- codeine series, for
example, libexin , synecode , etc.
As already mentioned, almost all severe cases of asthma uncontrolled by
bronchodilator aerosols are associated with widespread airway obstruction with
mucous plugs . IN THIS CONNECTION, I REPEAT AGAIN: IF THE BRONCHOR DILATIVE
AEROSOLS POORLY REMOVE A SHOCKING ATTACK, AND THE MUCISE IN THE FORM OF FIBER
OR STRANDS IS EXHAUSTED FROM THE LUNGS WITH GREAT DIFFICULT, THERE IS A POSSIBLE
OBTURATION (BLOCKAGE) OF THE BRONCH. forget about expectorants.