By Trishan Mistry
Analgesics are one the major branches of medication. It is a painkiller that can come in many strengths, treating pains of many serverities. Most of them can be purchased over the counter and are very common in most supermarkets. All of them are organic compounds which have many different functional groups, controlling their effects meaning that different types are more effective in different situations, for example, some of the drugs are anti-inflammatory. Most of these drugs are found under different brands or names such as Deep Heat or Lemsip but the actual medication has the same chemical formula and structure. There are 2 main types of analgesics. The first and most common are non-narcotic analgesics. These are common drugs used to treat mild pains, such as paracetamol and ibuprofen. They are most effective at helping cope with mild pains like headaches and muscular pains. The other type of analgesics is narcotic analgesics. These are much stronger drugs that are used to treat much more extreme pains, such as chronic pains or dealing with pain after surgery. While these medications are much stronger, some are still available over the counter for general use. To begin, the 3 main non-narcotic drugs are acetaminophen, acetylsalicylic acid and ibuprofen.
Acetaminophen is one of the most common analgesics and it is commonly sold in stores in the UK under the name paracetamol. The drug has the chemical formula C8 H9 NO2. It is very commonly used as unlike many other analgesics, it doesn't have a carboxyl group, meaning it has a greater pH than many others, making it much milder on the stomach. The drug can be formed by the synthesis reaction when acetic anhydride which is an ester and hydroxy aniline which is an aromatic compound react with the OH- nucleophile in sodium hydroxide and water, with the products of this reaction being the acetaminophen and a waste product of ethanoic acid.
Acetylsalicylic Acid is a drug used to treat mild to moderate pains, most commonly used to treat rheumatoid arthritis. It was first synthesised by a German chemist and used first during World War 1. After the Germans defeat, one of the statements in the Treaty of Versailles was that they had to give their recipe for the drug, so it arrived in Europe under the trademarked name that we commonly know now as Aspirin. Due to its carboxyl group, it has a very low pH and can sometimes cause stomach ulcers when taken. Therefore, this is helped by adding buffered aspirin which controls the pH. This is done as the buffer contains a number of carbonate and hydroxide ions which help increase the pH, preventing the formation of stomach ulcers and making the drug easier on the body.
Another one of the most common drugs found in supermarkets is ibuprofen. This is found very frequently under the trademarked name Nurofen. Similar to the others it is acidic due to its carboxyl group. This comes from the propanoic acid that its structure is loosely based off of. However, this drug isn't as damaging to the stomach lining as it is a much weaker acid than the others, having an average pH of around 3-4 whereas the previous drug has a pH of less than 1. The drug is synthesised through 4 main reactions. It starts with a mixture of isobutylbenzene and acetic anhydride. It begins with Friedel-Crafts acylation which is basically electrophilic substitution involving a benzene ring. Next is carbonyl reduction which is a type of nucleophilic addition. Then is a free-radical substitution involving chlorine. And lastly is a Grignard reaction where a Grignard reagent which is basically an organic compound in structure R-Mg-X where R is an organic chain and X is a halogen. This reacts with carbon dioxide and water to complete the reaction and form ibuprofen.
Narcotic Analgesics are the much more dangerous and addictive drugs that are regularly abused for recreational use. They are usually classed into opiates and opioids where opiates are the substances that are found naturally in the opium poppy. However, in recent years, opioids have been developed which are chemically the same substance but they have been synthesised in a lab following several chemical reactions. There are 3 main narcotic drugs that can have strains of both opioids and opiates. These are Morphine, Codeine and Heroin.
Morphine is one of the most well known narcotic analgesics due to its frequent use in medical injury. Morphine has incredible pain killing properties so therefore, it is used for severe pain relief, such as reducing pain after an organ transplant or it is given to a mother during labour or after childbirth. Morphine is taken by injecting it directly into the nervous system, this could be into the nerves in the muscles or more commonly into the spinal cord. It works by blocking pain receptors to the brain, giving a euphoric feeling, one that is often thrived for by addicts who tend to take the drug for their own personal pleasure. The molecule of morphine is an alkaloid meaning it is an organic compound containing an atom of nitrogen. There are 5 organic rings, with 3 of them being on the same plane and oxygen one being offset due to oxygen lone pairs and this one coming out of the plane. Since the atom has no carboxyl groups, it has a neutral pH, making it very easy on the body. One thing you may notice is that most of the narcotic substances have rings rather than the open ends of the non-narcotics. This gives less ends to be hydrolysed when the molecules are being broken down so they remain in your system for longer, giving them increased pain-killing qualities.
Codeine is a drug that has a very similar structure to that of morphine. In fact the only difference is instead of a hydroxide group here, there is now a methyl group. This occurs due to the high polarity in the bond between the oxygen and hydrogen, causing the electrons to move to the carbon in a molecule such as chloromethane. This causes a waste product of hydrochloric acid. The chlorine can be any halogen. SInce this group is now present, there are 3 more hydrogens exposed, meaning there are more ends to be hydrolysed in the body, increasing the surface area for enzymes to work on. This means it can be broken down easier, so it has less lasting effects than morphine but still much more than the non-narcotic analgesics. Unlike morphine, this is much easier to get hold of as it is present in strong cough syrups such as the formulation promethazine. These aren't available over the counter but they are frequently prescribed by doctors to suppress the cough reflex for flu patients.
Heroin is the last drug and once again it has a very similar structure to the previous two. Its main difference is the introduction of the two acetyl groups. This is formed when morphine undergoes an acetylation reaction, replacing the two hydroxyl groups with acetyl groups. When it was first synthesised, it was intended to be a less-addictive and weaker alternative to morphine as morphine was incredibly addictive. This was thought as there would be more ends to be hydrolysed, similar to how codeine is less addictive than morphine. However, once made, it was found that heroin is around 3-5 times stronger than morphine. This is because the acetyl group makes the molecule more lipophilic. This allows it to be transported through the phospholipid bilayers in our cells much easier, meaning it is more readily transported through the blood brain barrier. Therefore, more heroin can bind to the opioid receptor, blocking pain signals and giving the user a greater high feeling. Since then, scientists have found out much more about the threats and addictive qualities of heroin and therefore today, the use of heroin is being cut down massively in medicine. It is, however , still very prevalent in the recreational drug abuse world.