Medicines enter the body in several
ways. They enter through an inhaler, a skin patch, a pill, an IV, or
a hypodermic needle. Oh, you say I forgot an insulin syringe. Sorry
folks, the needle on the syringe is a hypodermic needle. The meaning
of hypodermic is under the skin and those of us injecting insulin do
inject it under the skin and hopefully into a layer of fat below the
skin and not in the muscle.
Medicines are also termed drugs and the
terms are used interchangeably. As the drugs make their way through
the body, changes happen along the path they travel. In this blog, I
will focus on drugs taken by mouth, since those are the most common
and many people with type 2 diabetes use them.
When you take drugs by mouth, they move
through the digestive tract and are taken up by internal organs like
the stomach and small intestine. Often, they are then sent to the
liver, where they might be chemically altered. Finally, they are
released into the bloodstream. As the bloodstream carries medicines
throughout the body, the drugs can interact with many tissues and
organs. Side effects can occur if a drug has unintended effects
anywhere in the body.
Drugs are treated just like food, as
the body attempts chemically to break them down as soon as they enter
the body. Most are broken down in the stomach or small intestine and
sent to the liver. The liver in turn contains protein molecules
called enzymes that chemically modify drugs and other non-food
substances. The chemical change of a medicine by the body is termed
drug metabolism.
Often, a drug is metabolized by the
body; it is processed into products called metabolites. These
metabolites are often weaker than the original drug, but sometimes
they have effects that are stronger than the original drug. An
example of this is the codeine in the prescription painkiller
Tylenol#3, which becomes fully active only after the medicine is
metabolized in the liver.
Since most drugs and other 'foreign'
substances are broken down in the liver, scientists often refer to
the liver as the 'detoxifying' organ. This means that the liver can
be damaged by too much medicine in the body. Drug metabolites
usually return to the liver and are chemically altered again before
they exit the body.
After a drug's metabolites have
circulated in the bloodstream and done their work as medicine, the
body eliminates then the same way it eliminates other wastes, in the
urine or feces. Age-related changes in the kidney function can have
significant effects on how fast a drug is eliminated from the body.
The above discussion helps explain in a
small way, how important the liver and kidneys are to the processes
that take place in the body for our drugs we take, and why many
researchers refuse to test drugs on the elderly. Not only are they
concerned about comorbid conditions, but also they are unsure of the
liver and kidney and how well the body can handle the medicines.
Yet, our doctors prescribe these drugs
and think nothing about the liver and kidney functions or the factor
of aging on our liver and kidneys. Think about this the next time
your doctor insists on keeping you on oral diabetes medications
instead of insulin.