Types of Medicines and Their Mode of Action and Use

These training materials provide short descriptions of the different types of medicine, how they work and how they are developed.

Figure 1. a) Simple structure of the chemical molecule paracetamol and b) the more complex structure of the biologic medicine insulin.

Biologic medicines in the broadest sense include any substance made in the laboratory from a living organism. This broad definition includes vaccines, immunotherapies, biosimilars, gene therapy and stem cell or tissue therapy. In this section, however, biologic medicines will refer to protein-based medicines, such as insulin, while the other substances covered in the broad definition will be described separately in different sections.

Background

The potential for vaccines to save lives was first discovered in the late 18th century, when Edward Jenner noticed that milkmaids who had previously contracted the cowpox virus seemed to be resistant to the similar, but more deadly, smallpox virus. To test his theory, he infected 8-year-old James Phipps with cowpox and then later attempted to infect him with smallpox. As expected, Phipps did not develop the smallpox virus, proving Jenner’s hypothesis to be correct. A global vaccination plan was implemented in the 20th century, which eradicated smallpox.¹ Vaccines are now available for preventing many previously devastating diseases, such as polio, typhoid, measles and tuberculosis, and have saved millions of lives worldwide. Indeed, today, vaccines are being used not only to prevent diseases, but also to treat diseases as well, such as cancer.

The spectrum of medical devices ranges from a simple pair of spectacles to improve eyesight, to the technologically complex magnetic resonance imaging (MRI ) machine used to examine organs inside the body. The World Health Organization and European Union definitions of medical devices can be condensed to:

An article, instrument, apparatus or machine that is used in the prevention, diagnosis or treatment of illness or disease, or for detecting, measuring, restoring, correcting or modifying the structure or function of the body for some health purpose.

Figure 1. https://commons.wikimedia.org/wiki/File:Inhaler2.jpg

Typically, medical devices are used when medicines alone cannot achieve the desired effect. However, medicine/medical-device combinations (often referred to as medicine–device) exist, such as the salbutamol–inhaler combination used by patients with asthma , and the adrenaline–injector combination for the treatment of anaphylaxis (a severe allergic reaction).

Background

Medical devices have been in existence for thousands of years. Records show the ancient Egyptians used scalpels, slings, splints and crutches as far back as 7000 BC. Some of the significant milestones in the development of medical devices are shown in Figure 2.

Figure 2. Timeline of medical device development.

Gene therapy is a way of restoring function in cells where genes are missing or not working properly. Genes contain all of the information for building and maintaining cells and are encoded by deoxyribonucleic acid (DNA ). The nucleus of every cell contains twenty-three pairs of chromosomes, in which thousands of genes are located. Certain diseases are caused by small changes in the DNA of our genes, known as genetic mutations. Mutations occur when information encoded by our genes gets copied incorrectly and this can lead to the production of faulty proteins which cause disease. Gene therapy is used to solve the problem at the source. This means that diseased tissues and organs can then work properly.