A pharmacist discusses why some medicines are taken orally while others are injected


How does aspirin know to travel to your head and relieve pain when you take it for a headache? It doesn’t, to put it bluntly: Molecules are unable to convey themselves across the body and have no control over where they end up. Researchers can, however, chemically change medicine molecules to ensure that they bind strongly where we want them and weakly where we don’t.

Pharmaceuticals are made up of more than simply the active ingredient that has a direct effect on the body. Inactive compounds, or chemicals that improve the stability, absorption, flavour, and other attributes that allow the drug to accomplish its job, are also found in medications. For example, the aspirin you take has chemicals that assist the tablet break apart in your body while also preventing it from fracturing during transportation.

For the past 30 years, I’ve been researching medicine delivery as a pharmaceutical scientist. That is, devising techniques and constructing non-drug components that aid in the delivery of a medication to its intended location in the body. Let’s follow a medicine from when it first enters the body to where it eventually ends up to better comprehend the thought process behind how different drugs are produced.

The process by which medicines are absorbed in the body

When you ingest a tablet, the medicine molecules first dissolve in your stomach and intestines before being absorbed into your bloodstream. Once in the bloodstream, it can travel throughout the body, allowing it to reach various organs and tissues.

Drug molecules have an effect on the body by attaching to certain receptors on cells that can cause a specific reaction. Despite the fact that medications are designed to target certain receptors in order to create a desired effect, it is hard to prevent them from circulating in the bloodstream and binding to nontarget locations, which could result in undesired side effects.

Drug molecules in your blood decay over time and eventually exit your body through your urine. Because of how quickly your kidney clears asparagusic acid, you may notice a strong odour in your urine after eating asparagus. Similarly, most multivitamins contain riboflavin, also known as vitamin B2, which causes your urine to turn a brilliant yellow colour when it is passed. Because the efficiency with which drug molecules pass the intestinal lining varies depending on the chemical features of the drug, some of the medications you take are never absorbed and end up in your faeces.

Because not all of the drug is absorbed, some medications, such as those used to treat high blood pressure and allergies, must be taken multiple times in order to replace drug molecules that have been lost and maintain a high enough level of drug in the blood to maintain the drug’s effects on the body.

Getting the right drugs to the right people at the right time

In comparison to pills and tablets, injecting a medicine straight into a vein is a more efficient technique of getting it into the bloodstream. This ensures that the entire medicine is disseminated throughout the body and that it does not degrade in the stomach.

Many intravenous medications are “biologics” or “biotechnology drugs,” meaning they contain chemicals obtained from other organisms. Monoclonal antibodies, proteins that bind to and destroy tumour cells, are the most frequent form of cancer medication. Because your stomach can’t recognise the difference between digesting a therapeutic protein and digesting the proteins in a cheeseburger, these medications are injected directly into a vein.

Drugs that require extremely high concentrations to be effective, such as antibiotics for serious infections, can only be supplied by infusion in some situations. While increasing drug concentration can assist ensure that enough molecules bind to the right locations to have a therapeutic impact, it also increases nontarget binding and increases the chance of adverse effects.

Applying the drug directly where it’s needed, such as putting an ointment onto a skin rash or using eyedrops for allergies, is one technique to acquire a high drug concentration in the right place. While some drug molecules will eventually be absorbed into the bloodstream, the amount of medication that reaches other sites will be extremely little and unlikely to produce negative effects. An inhaler, on the other hand, delivers the medicine directly to the lungs, avoiding side effects elsewhere in the body.

Patient cooperation is important.

Finally, getting patients to take medications in the proper amounts at the right times is a critical part of any drug development.

Because many people find it difficult to remember to take a drug numerous times a day, researchers aim to create therapeutic formulations that only need to be taken once or twice a day.

Similarly, tablets, inhalers, and nasal sprays are more handy than an infusion, which requires you to visit to a clinic and have it injected into your arm by a skilled practitioner. The easier and less costly it is to administer a drug, the more likely people are to take their medication when they need it. However, infusions or injections are sometimes the only efficient route to administer certain medications.

Even with all of the science that goes into fully understanding an illness and developing a successful treatment, it is frequently up to the patient to ensure that everything works as it should.