It seems like the more potent a drug/medication is, the more risks are involved with it, where as drugs with very little risk don’t help nearly as much.
In: Biology
It depends on what you consider a side effect. For a young, healthy person, there are many drugs which won’t cause any negative effects at all. For instance, most people who take acetaminophen (paracetamol) at appropriate doses for a headache will not experience any negative effects. Same goes for calcium carbonate tabs for heartburn, non-sedating antihistamines for allergies, etc.
There are about a bazillion listed side effects for almost any drug, but this is from large studies – if you take thousands of people with different genetics, ages, and health conditions, someone is bound to get negative effects from almost any medication. Likewise, taking any substance at much higher than the recommended dose (e.g. overdosing) will almost always result in negative effects – this is even true of something like water or food!
That said, if something is said to have absolutely no effects other than the intended one, there’s a good chance that it’s utter BS and doesn’t even do that (e.g. homeopathy).
The body has a limited set of tools to interact with. Some tissues and organs use the same tool in different ways. While one organ may take a screwdriver to tighten screws, another may use it to pry things, while one more may use it to poke holes.
When a doctor diagnoses someone with a few screws loose, the doctor could have the patient take a medicine that gives more screwdrivers. Sure that helps the one organ manage to tighten screws but the other organs, now with more screwdrivers, will start to pry more things and poke more holes. These unintended effects are side effects.
A real life example is the body’s response to opoids. Opoids are used as powerful painkillers because they imitate other chemicals in the body that block receptors that transfer the pain response to the brain. The same chemicals also trigger your gut to push your digested food down and out! One side effect of opoids is constipation. The drug brand Imodium, an anti diarrhea medicine, is actually an oral opoid that helps stop your gut from pushing too much. It’s dose is not high enough to cause the pain relief for the brain but people have tried abusing it this way.
If you want the drug to make a “change”, then you run the risk of side effects, and you are right that the magnitude of the side effects can be related to the size of the change.
Organisms are highly optimized, if it takes work to make a molecule then using the same molecule for many tasks is more efficient than making a different molecule for every task. When a drug changes the rate or production for the molecule, all the tasks that use it are impacted. Maybe you want to drug to change one task so you feel better, but the molecules are all impacted and there will be side effects.
Much of drug research is trying to make very exotic changes so that the net effect is more like what you want. Unfortunately, every person is different, and a different balance of tasks leads to a different amount of side effect.
You’ve mostly answered your own question: the downside to drugs that do a lot is that they do a lot, and the downside to drugs that don’t do much is that they don’t do much.
Drugs work by altering the production of neurotransmitters. For example, an antidepressant, an SSRI specifically, will inhibit the neurotransmitter serotonin in certain parts of your brain, but that inhibition causes the increase of serotonin in other parts of your brain, it increases it in the parts of your brain that will help with depression, but it also increases it in other unintended parts of your brain, that’s how side effects occur. Developing a perfect drug requires causing the increase of a/multiple neurotransmitter(s) in only the intended part(s) of the brain.
e: a word
Because all processes in the human body are connected and you can’t affect one without affecting others. It’s like throwing a pebble in water, you may want to hit a precise spot with your pebble and you can but you can’t stop the pebble creating ripples of water as it hits the surface.
Everything is connected in your body. Imagine giant dream catcher except all the strings are just one long string interwoven and perfectly symmetrical. If you pull at a string somewhere, something else moves. The bigger the change, the more something else is shifted. An illness is the dreamcatcher being uneven, and medication tries to fix the alignment.
Unfortunately thats why we have drugs to counteract other drugs. You want everything to be symmetric but if you move something you need to counteract it. somewhere else.
Quaaludes apparently gave a euphoric 2 hour high with zero side effects. So much so i’ve seen multiple people say how much they miss them because they were the best thing ever.
On top of all of your body’s biochemical overlap, which has been addressed in other comments, there’s a selective effect in which drugs get approved for use.
A more potent drug for a more serious condition might be worth enduring the side effects. You’d risk nausea and hair loss to save your life from cancer, but probably not to alleviate a headache.
Caffeine is actually a remarkable drug. It creates alertness without any serious side effects.
If it wasn’t so common we’d be amazed by it.
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