हिन्दी (Hindi) मे पढ़िये
Most people would prick up their ears at the above statement. In fact many people at some point of time in their lives have spent much effort in search of the perfect cough syrup. After all cough is a common and irritating symptom.
So, what is cough? It is the spasmodic expulsion of air from the inside of our lungs to the exterior. The air is expelled due to a sudden contraction of the chest wall muscles in response to a stimulus. The purpose is to dislodge and expel any matter trapped inside the airways. Trapped material may be mucous, blood, or a foreign body. Thus cough is a protective phenomenon helping to keep our airways free of obstruction thus allowing better oxygenation of blood. But sometimes there may be no material to expel from the airways. In such cases the cough is a result of irritation of the airway wall and may serve the only purpose of being a nuisance to the person coughing.
Cough may be caused by many mechanisms like:
1. Direct irritation of the airway wall by material introduced from the outside environment or material abnormally produced from within our lungs such as pus, mucous or blood. Such abnormal material is produced during disease states like pneumonia, abscess to name a few.
2. Allergic mechanisms in which the airway becomes hypersensitive to otherwise normal stimuli like dust, cold air, or drugs. One common disease causing such hypersensitivity is bronchial asthma. It is common for asthma to run in families, usually affecting people from childhood and sometimes presenting only cough.
3. Drugs like ACE inhibitors are another common cause for cough in which case the cough subsides if the drug is withdrawn. Ace inhibitors like Ramipril are commonly used as antihypertensives and cardiac medication.
4. After many viral infections involving the upper airways like throat in which the the airways are irritated producing a cough.
5. Smokers tend to have a chronic (longstanding) cough which is mostly irritating to others than themselves. This is because they themselves get habituated to the cough.
The importance and the treatment of cough would obviously depend on the cause of cough. A discussion of the various treatments available depending upon the diagnosis (establishing the disease process responsible for the cough) of the disease is outside the scope of this discussion.
So, where exactly does the cough syrup come into the picture. Traditionally the cough syrup used to be mixture of ingredients. Different ingredients have different actions with sometimes seeming opposite action.
1. Cough suppresants: Codeine is the prototype drug with cough suppressing action. It is useful for people with dry irritating cough which apparently serves no purpose in clearing the airway. It is particularly useful when there is coughing up of blood which needs to be stopped. Codeine is an opioid which is a derivative of opium the well known narcotic which is traded in the illicit drug market. This is why cough syrups containing codeine or its congeners are prone to misuse by addicts, especially so because it is easily available over the counter. Teenagers are particularly prone to this form of addiction.
2. Expectorant: This supposedly is to facilitate the cough in expelling the abnormal produce of the lungs. Guaifenesin is an example.
3. Mucolytic: A substance which reduces the viscosity of mucous to ease the expectoration (expulsion of mucous). Bromhexine is an example drug. Utility is doubtful.
4. Antihistaminic: Apparently reduces the allergic or hypersensitive reaction of the airway thus alleviating the cough. Chlorpheniramine is an example of this group.
5. Decongestants: These are used to dry up the mucous membranes in cases of excessive secretion. Pseudoephedrine is an example.
Cough syrups available over the counter are different combinations of the above mentioned drugs. Hundreds of cough syrup brands are sold in India. And believe me, no two cough syrups are alike! A Times of India report says that cough syrups are the leading selling brands in India (1). A Cochrane Collaboration meta-analysis (an analysis of available literature) shows that there is no evidence either in favour of or against over-the-counter-cough medication for acute cough in children or adults (2). This of course is a generalized statement. A few special situations are given below:
1. Decongestants like pseudoephedrine are also known to cause hypertension.
2. Antihistamines cause sedation and are not suitable for people who need to remain alert like drivers or machinery operators.
3. The potential of opioids to be abused has already been discussed.
Recently the US Food and Drug Administration (FDA) has removed about 500 unapproved cough and anti allergy medications from the US market (3). This serves to prove that such medications have proliferated unnecessarily in the market and that the manufacturing companies target an unaware and cough syrup hungry population. The extent of advertisement is such that patients are unhappy if their doctor does not prescribe them the best cough syrup. This problem can be solved with patient education and strong legislation.
2. The Cochrane Collaboration Meta-analysis of over-the-counter- cough and cold medications in children and adults: