Although biology may be the subject we all think of when it comes to medicine, when we zoom into the bigger picture, chemistry is what provides the building blocks for the foundation of medicine. This pertains to both our understanding of the body itself, but it also helps us create new treatments in order to figure out how they will react with humans once used. The below is by no means an exhaustive list but will hopefully provide an insight into the vast array of uses it has.
Optical isomerism
Despite learning about molecules in 2D, it’s important to remember that they exist in a 3D space. Optical isomerism (when molecules have the same molecular and structural formula but form two non-superimposable mirror images) is a phenomenon that can occur in some drugs, and this can affect their manufacture, efficacy, and side effects. For example, Ibuprofen is a mixture of two optical isomers, but is mostly sold as a racemic mixture (equal parts of the two mirror-image isomers) as one isomer has an anti-inflammatory effect, while the other has none.
However, other drugs can have an isomer that is harmful to the patient. Naproxen, a drug with one isomer that treats pain from arthritis, has an another that causes liver poisoning. Thalidomide was marketed as a safe drug to treat morning sickness but was later discovered to cause birth defects in about half of the children born to those who took it. The drug was sold in a racemic mixture, but one of the isomers caused these birth defects. If a drug has optical isomers, a manufacturer has three options: separate the isomers (which is often tricky or expensive), sell the drug as a racemic mixture (which is the case with Ibuprofen), or design a process to manufacture the drug that only produces the desired isomer.
Acid-base reactions
Acid-base reactions are used frequently in everyday life. The reaction of hydrochloric acid and sodium hydroxide creates sodium chloride (table salt) and water. This concept is the same one used in antacids, which neutralise the excess stomach acid to relieve indigestion and heartburn. One such example is magnesium hydroxide, found in milk of magnesia.
Ligands
Ligands are ions or molecules that form a coordinate bond (a covalent bond where both electrons come from the same atom) with a transition metal by donating a pair of electrons. These molecules are used in chelation therapy, which is a treatment for heavy metal poisoning. The ligands can bind to the excess metals in the body, which allows them to be excreted.
Polymerisation
Prosthetic implants have to be made of carefully selected materials to ensure they last. Crucial, if they are replacing a worn-out joint – for example hip implants, which are intended to replace a damaged hip joint. Hip implants have undergone many iterations, first made from ivory and nickel in the 19th century, and eventually transitioning to metal and acrylic prosthetics in the 1950s. However, these were prone to wear, so they were later replaced with the polymer, polyethylene.
The ability to understand and synthesise these materials is essential to the improvement of prosthetic technology. Further research has led to an improved form of polyethylene – cross-linked polyethylene – which is made by radiating and reheating the polyethylene. This strengthens the plastic’s molecular structure, allowing it to have lower wear rates.
Contrast agents
In order to increase the contrast in imaging such as x-rays, MRIs and ultrasounds and to improve the visibility of internal body structures, contrast agents are used. Barium sulphate is primarily used to increase contrast when x-raying the digestive system. Understanding the solubilities and toxicities of these agents is important, so that we can predict how they will act once ingested or injected. Barium compounds are usually highly toxic, however, barium sulphate is virtually insoluble, so it can be ingested without harmful amounts of the metal being absorbed by a patient.
Manufacture of drugs
Lastly, chemistry is what allows us to manufacture drugs to treat illness. Acylation is a process used in the creation of aspirin (aka acetylsalicylic acid), a painkiller. Understanding atom economy and percentage yield allows us to maximise the quantity of a drug produced to make drug manufacture cheaper and more efficient.
The importance of chemistry to medicine cannot be understated, and reaches far further than the list above. Medicine is an area where not just the sciences, but also other areas such as anthropology, combine, in order to create an extremely unique discipline.
