The myth of a drug to treat all types of cough

Cough, fundamentally, can be categorized into two types based on its nature: dry or productive with phlegm.
However, it can be further classified into fifty types based on the cause.
For instance, a cough could be due to:
Heart muscle failure, ACE inhibitors usage, asthma, immunological reactions, post nasal discharge, chronic obstructive lung disease, rheumatoid conditions, emphysema, asbestosis, pulmonary arterial hypertension, pulmonary embolism, and many others.

If we focus solely on its nature, we can say that the dry cough has a mechanism opposite to that of a productive cough with phlegm.

In the case of a dry cough, our lungs have something called cough receptors. These receptors sense stretch, temperature, and pain, sending signals to the cough center through the vagal nerve. Why? To initiate the cough reflex and inform the brain about something foreign or problematic, prompting the person to cough and expel it.

The problem here could be either peripheral in the lung receptors or central in the cough center in the brain. The primary treatment is to suppress the cough reflex, either with local medications or central anti-tussive drugs. The crucial point is whether it is acute (lasting less than 3 weeks, usually due to infection) or chronic (lasting more than 8 weeks, with various causes, as mentioned above).

As for a productive cough, it involves phlegm or mucous in the bronchi tree, which, if not expelled, can accumulate in the alveoli and cause issues like Lower Respiratory Tract Infection (LRTI).

The solution involves two aspects. First, we need to take substances that reduce the viscosity of the mucous, making it easier to expel. These are called mucolytics, and they work through different mechanisms, either breaking the peptide bridge or increasing the water content to decrease viscosity.

The second aspect is to facilitate the expulsion of the thinned mucous. For this, we take expectorants, which induce irritation to the cough receptors, activating the cough reflex. This is contrary to the action of anti-tussive drugs.

Consequently, it's challenging to find a single medication that treats both dry and productive coughs. Unfortunately, the science has not yet fully understood the mechanisms behind these drugs for cough treatment.