There are many different types of cough preparations, generally falling into two categories: supressants and expectorants. Although many entice sufferers with "natural" ingredients such as lemon, honey and blackcurrant, a quick glance at the label r
Supressants can contain narcotics, the most common being codeine (though diamorphines, and methadone can also be used). Apart from a small risk of dependence, these can cause constipation, urinary problems, depressed breathing, dizziness and nausea. Non narcotic supressants cause many of the same symptoms and those containing dextromethorpan should not be used by those taking MAO inhibitors or who have asthma (or any chronic cough) or liver disease.
Expectorants containing antihistamines such as diphenhydramine hydrochloride can irritate the stomach lining, raise blood pressure, cause fluid retention, drowsiness, thirst and rapid breathing.
Remember, coughing is the body's way of removing mucous. Taking supressants is counter productive. If you must take cough medicine, stick to those which have a single main action.