Most medicines have two names, one which describes the chemical which is the active principle, often referred to as the generic name, and the second, the manufacturer's own trade name. For example, oxytetracycline hydrochloride (OTC) is the generic name for a broad spectrum antibiotic. Terramycin is the trade given to it by Pfizer Ltd. Other trade names for the same medicine include, tetramin, duphacycline, engemycin and so on. These vary from country to country. Throughout this book the generic names are used with references to some commonly used trade names.

You will be familiar with the trade names of medicines used on your farm but also try to remember the generic names, because this will help you to understand how they function and how to identify them irrespective of a trade name.