Let's look at the connections between medication and the brain in two ways:
While relative terms like good and bad may be a bit to general for some, it is important that we take as simplistic a view on this situation as possible. The "noise" around the issue of pharmaceuticals is enormous and whether it is prescription or over the counter medications we are speaking about, the realities are the same. These things can be either good or bad for the brain.
Before we look at the good versus bad ways that medications connect to brain function, we need to understand the "blood-brain barrier". The BBB effectively stops many pharmaceuticals from passing into the brain itself. This is due to the cells within the brain, which are "functionally distinct from the blood" (Nature) The BBB controls what gets into the brain and what stays out - keeping the brain surrounded by extracellular fluid that ensures it gets oxygen and nutrients, and nothing else.
However, modern drugs have been engineered to overcome the BBB or to change the brain environment in ways that cause serious problems. Depleting the brain of fat or impairing nerves, some drugs harm or impair the brain. On the other end of the spectrum, some supplements and medications provide immense support to the function and health of the brain too.
A "bad news first" approach to this topic is probably the best. The preponderance of news stories and articles about medications and their harmful effects can make it difficult to understand the worst risks to the brain. We can learn how one drug or another might raise blood pressure, expose us to greater risks for chronic diseases, or have lethal side effects. But just what do certain compounds do to our brains?
It is easy enough to learn that statins, the drugs given to us when we have dangerously high cholesterol levels, "inhibit neurotransmitter production which leads to impaired memory and other cognitive functions". Thus, we see the rise of dementia-like conditions with the rise of anti-cholesterol drugs. We also know that drug abuse can cause long-term changes in the brain because of their effects on synapses and our "reward system".
So, certain drugs are most definitely bad for the brain, and this can lead us to wrongly believe that all medications may pose risks.
Fortunately, there are "nootropics". These are also known as "smart" drugs because of the ways they directly benefit our brains, helping to enhance such things as memory, cognitive function and more. They are able to make their way safely through the BBB because they rely on synergistic combinations of natural compounds.
A prime example of this is thiamine that can cross the BBB and be combined synergistically with other nootropics to help boost brain function and health. Now, you might read that and think, "thiamine is on the list of things in my daily vitamin" and you would be correct.
This is because nootropics include "functional foods" and "nutraceuticals" (foods with medicinal benefits), and are not authentically described as "drugs" in the classic sense.
Popping a pill or swallowing a prescription compound triggers a series of events that allows certain materials to enter the blood stream and to then be used by the body as intended. Microscopic as these materials might be, some can pass through the protective barrier around the brain or alter the environment that your brain inhabits, creating many unwanted changes.
One way to help the brain is to use compounds meant to protect it or help it function at optimal levels. Nootropics are a large group of safe and effective compounds and even foods or supplements that should be seen as offering "good ways" for drugs to interact with your brain and promote its long-term health.
Nature. Drug transport across the blood–brain barrier. http://www.nature.com/jcbfm/journal/v32/n11/full/jcbfm2012126a.html