(1994; 115 pages) [French] [Spanish]
What is your first-choice treatment for dry cough?
Rather than reviewing all possible drugs for the treatment of dry cough every time you need one, you should decide, in advance, your first-choice treatment. The general approach in doing that is to specify your therapeutic objective, to make an inventory of possible treatments, and to choose your ‘P(ersonal) treatment’, on the basis of a comparison of their efficacy, safety, suitability and cost. This process of choosing your P-treatment is summarized in this chapter and discussed in more detail in Part 2 of this manual.
Specify your therapeutic objective
In this example we are choosing our P-treatment for the suppression of dry cough.
Make an inventory of possible treatments
In general, there are four possible approaches to treatment: information or advice; treatment without drugs; treatment with a drug; and referral. Combinations are also possible.
For dry cough, information and advice can be given, explaining that the mucous membrane will not heal because of the cough and advising a patient to avoid further irritation, such as smoking or traffic exhaust fumes. Specific non-drug treatment for this condition doesn’t exist, but there are a few drugs to treat a dry cough. You should make your personal selection while still in medical school, and then get to know these ‘P(ersonal) drugs’ thoroughly. In the case of dry cough an opioid cough suppressant or a sedative antihistamine could be considered as potential P-drugs. The last therapeutic possibility is to refer the patient for further analysis and treatment. For an initial treatment of dry cough this is not necessary.
In summary, treatment of dry cough may consist of advice to avoid irritation of the lungs, and/or suppression of the cough by a drug.
Choose your P-treatment on the basis of efficacy, safety, suitability and cost
The next stage is to compare the various treatment alternatives. To do this in a scientific and objective manner you need to consider four criteria: efficacy, safety, suitability and cost.
If the patient is willing and able to follow advice to avoid lung irritation from smoking or other causes, this will be therapeutically effective, since the inflammation of the mucous membrane will subside within a few days. It is also safe and cheap. However, the discomfort of nicotine withdrawal may cause habituated smokers to ignore such advice.
Opioid cough depressants, such as codeine, noscapine, pholcodine, dextromethorfan and the stronger opiates such as morphine, diamorphine and methadone, effectively suppress the cough reflex. This allows the mucous membrane to regenerate, although the effect will be less if the lungs continue to be irritated. The most frequent side effects are constipation, dizziness and sedation. In high doses they may even depress the respiratory centre. When taken for a long time tolerance may develop. Sedative antihistamines, such as diphenhydramine, are used as the cough depressant component of many compound cough preparations; all tend to cause drowsiness and their efficacy is disputed.
Weighing these facts is the most difficult step, and one where you must make your own decisions. Although the implications of most data are fairly clear, prescribers work in varying sociocultural contexts and with different treatment alternatives available. So the aim of this manual is to teach you how, and not what, to choose, within the possibilities of your health care systems.
In looking at these two drug groups one has to conclude that there are not many alternatives available for treating dry cough. In fact, many prescribers would argue that there is hardly any need for such drugs. This is especially true for the many cough and cold preparations that are on the market. However, for the sake of this example, we may conclude that an unproductive, dry cough can be very inconvenient, and that suppressing such a cough for a few days may have a beneficial effect. On the grounds of better efficacy we would then prefer a drug from the group of opioids.
Within this group, codeine is probably the best choice. It is available as tablets and syrup. Noscapine may have teratogenic side effects; it is not included in the British National Formulary but is available in other countries. Pholcodine is not available as tablets. Neither of the two drugs are on the WHO Model List of Essential Drugs. The stronger opiates are mainly indicated in terminal care.
On the basis of these data we would propose the following first-choice treatment (your P-treatment). For most patients with a dry cough after a cold, advice will be effective if it is practical and acceptable for the patient's circumstances. Advice is certainly safer and cheaper than drugs, but if the patient is not better within a week, codeine can be prescribed. If the drug treatment is not effective after one week, the diagnosis should be reconsidered and patient adherence to treatment verified.
Codeine is our P-drug for dry cough. The standard dose for adults would be 30-60 mg 3-4 times daily (British National Formulary). Noscapine and pholcodine could be an alternative.