How Do Medicines Work In The Body?

What happens to medications once they are in our bodies? Where do they go? How do they get there? What functions do they carry out?

Millions of pills, syrups and potions are ingested in some form or another by humans on a daily basis. It may then be beneficial to us all to know exactly what happens inside our bodies when we have taken some form of medication.

Medicines work in a variety of ways depending on what they are taken for and in what form. Some examples of what we take medicine for are:

• pain relief
• to fight infection
• to fight disease
• to supplement a deficiancy
• to assist a body mechanism to correct itself
• to decrease an over abundance of a body substance
• to balance systems and organs in the body

But in addition to what we take, there is also the route and form by which a medication is taken:

• oral - tablet, capsule, syrup, drops etc.
• sublingual, (under the tongue) - tablet, drops.
• skin preparation - cream, ointments, gel, patches etc.
• injection - by hypodermic syringe
• IV - Intravenous - needle into a vein.
• Into the bowel - suppository/enema
• inhalation - steam inhalation, crystals, inhaler
• drops - ear/eye/nose

How medicines are processed by the body is intricate but we can simplify this by breaking the steps down into four main areas:

• Administration - we take or are given the medicine as mentioned earlier
• Delivery - once the medicines are inside our body they move into the blood stream then into organs and tissues.
• Performance - medicines will produce or induce effects.
• Elimination - the body will wash out medicines and waste products associated with them.

So the type and route will have an affect on where the drug will enter the body and what areas the drug may target. For example, inhalations are primarily to assist with breathing in some form or other. Whether it be through 'over-the-counter' medications or inhalers prescribed by a doctor for asthmatic patients. The route and type of medication also has an effect on how quickly a drug will act. Intra-venous (IV) is a rapid method of medication administration, since the chemicals enter directly into the blood stream. Injections into a muscle, full of blood vessels is fast. Or Suppositories and enemas can also be swift acting. This is due to the large surface area of the bowel that is packed with blood vessels, so absorbing the drugs very quickly. These last 3 routes also by-pass the stomach where some or all of the drug could be destroyed or diluted by the hydrochloric acid in the stomach.

But by far the most common route is taking medication by mouth - the oral route. From here the medication has a journey to make that starts from our mouths to the target area.

Drugs In The Digestive System

Once medicines reach the stomach they may start to dissolve. However, some pills that are in capsule form will remain intact until they reach the small intestine. This is because if the capsule was to disintegrate in the stomach the contents would be destroyed by the hydrochloric acid. Therefore some medications, are sealed in special capsules to survive the stomach. They are then absorbed through the lining of the small intestine. Medications are then carried into the blood stream - moving from a high concentration fluid in the intestine to a lower concentration fluid - the blood.

The Circulatory System

No matter what form a medicine takes they will be dissolved and enter the blood stream at some point. In this form the medicines are circulated around the body and so delivered to organs and tissues. This process is very fast. The heart can pump a full cycle of blood in about one minute. During this process the medicine molecules are being delivered throughout the body. The brain will receive the largest portion - about 16%. We will talk about the brain in more depth a little later. The effects of the medicine will continue to be active until *metabolism begins.

The metabolism for each medicine is different. In other words some are broken down and prepared for elimination more quickly than others. That is why some medicines will be given frequently, for example 2-4 hourly, others less so. In fact some medicines may already be breaking down when they passed through the liver for the first time - this is called 'first-pass effect' . Some form of tablets and capsules may have to go through the liver several times before they can be eliminated from the body.

(*Metabolism - the biochemical activity of a substance within a living organism.)

Within the body tissues and cells

Within the body tissues we eventually get down to the cellular level. The cells of the body can absorb fluids and so will soak up the molecules of medicine within blood fluid that surrounds them. Not all medicines will start to work at the same time. This is because different medicines all have their own specific molecules that will dissolve either quite quickly or more slowly than others. In addition some medicines find it easier to dissolve in human tissue than others. Human cell membranes have a high content of fats. Therefore if you have a medicine that can dissolve in fat then they will begin to work more quickly than those that can't. This ability to dissovle in fat is a very important point on how fast a drug will begin to act in the body. Once the dissolved medications are within the cell this is where most of them do their work through biochemical reactions. They then re-enter the blood stream where they will once again enter the liver. Here they will be broken down further and prepared to be eliminated by the body.

Elimination

The main organs associated with elimination of medicines is the liver and kidneys. Basically these organs sieve out toxic substances. The liver breaks them down through a series of complex metabolic reactions. These toxins/waste products are stored by the liver until it is ready to send them to the kidneys. In the kidneys the prepared substances are further processed and then eliminated from the body through the urine.

How do medications interact with the brain?

As mentioned earlier medicines enter the blood stream once they have been dissolved and travel throughout the body to various organs. This obviously includes the brain. Once in the brain some medications can affect chemicals called neurotransmitters. These are special chemicals that are responsible for and control the transmission of messages between brain cells called neurones. Specialised Neurotransmitters are also responsible for having an affect on people's feelings and moods.

However, it is not always possible for medicines to get access to the brain. This is because the brain has a safety device called the 'blood-brain barrier' - BBB for short. This in effect helps to prevent things such as bacteria, toxins and unwanted molecules from entering the fluid that directly surrounds the brain. But what this does mean is, if infection infiltrates the defences then medications such as anti-biotics, whose molecules are large, cannot cross the BBB to fight the bacteria. Having said this, with infection comes inflammation and this is one condition that will weaken the barrier and may allow anti-biotics to filter through. Other medications that are required to access the brain directly need to have specialised fat-soluble properties in order to get through the BBB's defences. In some areas of the brain the BBB is deliberately weak. This allows the brain to monitor the composition of the blood and to take action if adjustments are needed.

There are conditions and disease that can weaken the BBB to a dangerous level that would allow other harmful substances to pass through. Some of these conditions are:

• Hypertension
• Very high exposure to microwaves and radiation
• Infections
• Head trauma
• Ischaemia - disease in the circulation causing lack or no blood supply to tissues
• Inflammation
• Pressure
• Meningitis
• Epilepsy
• Multiple Sclerosis
• Alzheimers disease
• HIV Enchepalitis
• viruses

and many others.

There are quite a number of factors that will influence both the absorption rate and the metabolism of medicines. They could also influence how effective the medication is.

Physical

This includes your weight, age, fat mass, muscle mass etc. All these factors either speed up medicine absorption or slow it down. If you have a good amount of fat mass for example, then it will have an affect on how long it takes to target the specific area and how effective the medicine still is when it gets there. In relation to age - younger people tend to be able to metabolise and eliminate medications quicker and more thoroughly than older people. Therefore doctors will often moderate the dosage of tablets etc., for an elderly person. Babies and young children have to have a moderated dosage as well since their bodies are still maturing. This means their organs could be more easily damaged either by the toxic affects of medicines or too strong a dosage of less toxic ones.

In addition, we are all genetically and chemically different. Some of us may tolerate a particular medicine more than others. This is why some people may suffer from either the *side effects or **adverse affects of a medicine.

• *Side effect - "...un undersirable secondary effect of a drug or other form of medical treatment..." Encarta Dictionary.
• ** Adverse effect - "...creating unfavourable, undesirable or harmful results from a medication..." Encarta Dictionary.

If you experience any problems with medicines you should consult your doctor or pharmacist immediately. In addition if you or anyone you know accidently take too much medication contact the same people. Keep the bottle/packet that the medication came in and any remaining medication within the packaging. A doctor or pharmacist may want to see these.

Food

Food will slow down the absorption rate of medication. This can either be beneficial or detrimental to the medications success rate. That is why it is always important to follow the instructions given either by a doctor or on the leaflet if bought at a chemist. As an example, instructions may include:

• To be taken before food
• To be taken either with or after food
• To be taken after food
• To be taken with a full glass of water

Other Medications/Chemicals

These can also have an effect on medications. The effects are numerous and varied. For example if some medications are taken at the same time, they could cancel out the benefits of each other. Some medications/chemicals will increase or decrease the rate of absorption and metabolism in the body. So again, that is why it is important to follow the instructions given to you or that are stated on instruction leaflets. For example you may see an instruction such as:

• Not to be taken with alcohol
• Do not operate machinery, or drive while taking this medication