This question came about as my wife has just started a course of steroids to treat her Crohn’s Disease. They work amazingly well, amazingly quickly… But they are only a temporary solution as they have a range of significant side effects such as thinning of the bones, insomnia, etc…
Steroids are “old” in medical terms – why haven’t we managed to remove the side effects yet?
In: Chemistry
An effect for one person is a side effect for another. I believe the use of Viagara for erectile dysfunction was originally seen as a side effect. Its original purpose was to treat hypertension and angina.
When you take a drug orally, you are flooding your bloodstream with a chemical. It is intended to go where it is needed, but it will go everywhere else, too.
Of course, they keep trying to find drugs that only have *one* effect, the intended effect, but they can’t always find a perfect drug like that.
In some cases the drugs can actually be modified to reduce side effects. A common example is the allergy medicine Xyzal, which is a newer version of the medicine Zyrtec, but they managed to get rid of the drowsiness effect that Zyrtec had. Another one would be Imodium, which is similar to morphine and binds to opioid receptors in the gut and brain, just not so much the ones that make you high. So in some cases it’s the structure of the drug itself that is able to be changed to cause less of a side effect, other times it can be changed to be more specific in the receptors it targets. But someone smarter than me may be able to explain why steroids seem to be so hard to reduce side effects.
Side effects aren’t something that can be removed from a specific drug. The drug does what it does, and some parts of that aren’t desirable. If we were to change the drug it would do different things, in which case we aren’t removing the side effects but using something else. It might be helpful to think of what we call side effects as something “extra” that happens. It’s more like the drugs just do all of that, and the stuff we don’t like at the moment are side effects. We call wildflowers weeds when we want a lawn, but a treasure when in the park.
This is kind of like asking why we don’t make metal knives that don’t cut fingers. We’ve had metal knives for thousands of years, surely we can make one that is sharp, but cannot cut fingers.
All medications have side effects. Your body is a huge, complex network of many different cells that have many different functions. When you flood your bloodstream with a foreign chemical, that chemical has all sorts of effects depending on where it goes and what cells or processes it interacts with.
To simplify, think of your cells and medications as puzzle pieces. Your cells have lots of different shapes that can accept lots of different puzzle pieces. A medication is a puzzle piece that could fit in many different places even if it’s not a perfect fit. Generally, we try to design medications so that there aren’t many places it can fit in your body, which results in side effects being less common.
For the “old” medications you mention, a lot of it is economical. If an old medication works with side effects that are mainly discomfort and aren’t long-term harmful, it doesn’t make sense to invest the billions of dollars to make marginal improvements and try to eliminate the already few side effects. It makes much more sense to invest those billions on new cancer drugs, for example.
Well, the simplest ELI5 reason is that everyone is different. When you design a drug, you do as much as you can to ensure it will work as intended. However, its effects also depend on one’s genes, diet and lifestyle, age, other health issues and if this person takes any additional drugs. There are so many variables outside your control, that among a large group (thousands) of people, you will always find several individuals for whom your treatment isn’t effective or causes some bad side effects. That is because they can have some unique combination of conditions listed above.
EDIT: I want to add the second part. With any modification you risk introducing new side effects. Yet, this industry is constantly improving, we find better and safer drugs all the time. It’s true that for some health issues it is harder. Some of it is due to the fact, that these drugs have to mess with crucial processes in your body to be effective. This makes finding a substance which will do the job without causing serious problems down the line extremely difficult.
It’s part of the intrinsic properties of the medications we are using.
Simplest example I can use right now is caffeine. We use it to stay awake. But what is a side effect? It keeps you awake when you don’t want to. Now it does a bunch of other things too, but I feel it’s a great starting point for understanding that side effects can’t just be removed. You’d have to use a different chemical that produces the desired effect.
There are different types of side effects. On-target side effects are intrinsic to the medicine and can’t be removed. Off-target side effects can be mitigated by making a more selective drug.
Steroids, for example, have significant on-target side effects where the same biological target can cause a benefit in one organ/tissue but a side effect in another organ/tissue. Steroids also affect many different biological targets and specific steroids work better for certain diseases.
Because substances will have different effects on different parts of our body. Or even if it only affects one specific thing, that might then trigger a bunch of other things. Too many things are connected, no matter what you do, something else will usually happen.
They can and do find out how it affects the whole body. And then evaluate whether the negatives are worth the positive effects. If so, it’ll pass certification. And sometimes, a new drug is developed that perhaps does the same positive thing but fewer negatives because the mechanism is different.
Because the human body is a damn mess. Every chemical in your body is doing like five wildly different jobs depending on where in the body it’s located and medicine is trying to adjust *one* of those jobs without affecting the others.
Sometimes you manage to find a chemical or combination of chemicals that together affect only the desired biological system but usually we only figure out one or two of a dozen different factors and hope adjusting those doesn’t throw something else out of balance.
Side effects are not a by product or a contaminant, they are just affects which are different from the desired, theraputic affect. it, they often cannot be ‘removed’ without also canceling the desired affect. Often, another med might be found where the other affects are not as much of a problem, in other cases, one must weigh the trade off. I for one, would be happy to have all my hair fall out and be cured of cancer….. and so on.
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