why do some medicine take an hour to kick in and some like anti depressants take weeks to work?
In: Chemistry
I remember my doctor explaining antidepressants have to build up in your system to allow serotonin or dopamine to build up to a normal level. The medication doesn’t release “feel good” hormones, it basically slows down processes to let the hormones build up. I may be wrong, but that’s how I recall it working in simple terms
Medications have different mechanisms of action. They affect different systems in the body, in different ways. Your body absorbs them in different ways.
For a medication to start working, enough of it needs to reach the site it affects to have the desired effect, and then your body will respond to these chemicals. Ibuprofen will hit your bloodstream pretty quickly and reach the site of inflammation where it will suppress your body’s inflammatory response; that process happens quickly because inflammation does. It’s something your body does very rapidly in response to injury.
Changing the level of neurotransmitters in your brain is a much slower biologocal process and doesn’t happen as easily. The concentration of antidepressants needs to build up until it is enough to change your brain’s processes. This takes time to happen.
The real answer is we don’t have a good understanding of how/why SSRIs work. It is counterintuitive, as you point our, that it takes much longer to see an effect after teaching steady state levels in the blood (usually achieved after 4th dose).
Its all about getting certain chemical levels in your body.
For example, Acetaminophen (Tylenol) works by slowing your bodies production of Prostaglandin. This chemical is what causes inflammation in the body, so by preventing this process we can quickly eliminate minor pain and inflammation.
Most anti-depressants on the other hand work by stopping your body from absorbing positive brain chemicals such as Serotonin. In order to have a noticeable effect, your body still needs to “catch up” by producing serotonin at a normal rate in order to build up high enough levels to notice a change in feeling. The reuptake is just reduced meaning you can slowly elevate your overall serotonin levels without losing the serotonin your body already produced.
The most common antidepressants are the serotonin re-uptake inhibitors and similar drugs. This means that in the brain, they block serotonin from being ‘vacuumed’ up, and leave it around to do its job longer. They do this right away, as soon as they are absorbed and get to the brain, just like other drugs. But since they don’t ‘work’ right away to help with depression, something else must being going on. What is happening is that the brain responds to more serotonin sticking around by altering itself. This means changing connections between neurons, changing how well neurons respond to serotonin, how much serotonin or other signaling molecules they make, etc. This is what takes time. We don’t know exactly how the brain is changing, just that something like this must be happening.
You ha r to build up a therapeutic level. The medicine gets in you at such a level everytime you take it. But your body throws most of it out. So maybe you get like 15% that hangs out for a bit.
So every day you keep adding 15% mote until it’s built up in you.
That’s a rough generalization, but it’s how I explain on-boarding here.
Antidepressants work right away as far as what they are intended to do. It’s just the action of the drug results in your brain remodeling in order to adapt to this change. The remodeling process is slow. Small changes every day. Over time the small changes build up to something tangible and change how your brain works.
What the drug does and the beneficial effect are related, but not necessarily the same. Here are a couple examples:
Medicines like antacids help your heartburn quickly because they act as a base to neutralize the acid that is causing you pain. It’s a quick process and pain response changes quickly.
Another medicine that can help with pain is Capsaicin cream. When you first start using it, it can cause more pain because it causes an intense burning feeling. That feeling is so intense that your “this hurts” nerves run out of the chemical they use to tell you things hurt after being overstimulated by this cream for a few weeks. This takes a lot longer than Tums because the way they help with pain is so different.
To go back to your example of antidepressants, we have a lot of different types of those. Some affect different neurotransmitters or combinations of them. They have this effect within a couple days, but regardless of what they’re doing, we always see a response starting after about 4 weeks. Basically, the chemical soup your brain is sitting in has changed, but that change doesn’t fix depression directly. Your brain has to change in some way in response to the new soup. This brain change is what helps with the depression. So, we make new drugs all the time, but they can’t work faster because the thing that takes so long is the human brain, not the drug.
It more-or-less has to do with the half-life of the medication and how your body metabolizes the medication and blood levels required to be therapeutic.
I don’t think a 5-year-old would understand that but I don’t know how to simplify it any further.
So, the way drugs work depend on the way they move through out the body and the way that they affect your biology to fix the problem.
You can think of your body as a hugely complicated machine with many interconnected mechanism.
Some of these mechanisms work very fast. For example, a nerve cell can fire an impulse in a fraction of a second.
Other mechanisms work very slowly. For example, if you get a cut on your skin, it could take days or weeks for your body to form a scar and then heal.
There are slow processes in your body that are as slow as wound healing but we can’t see because they either happen internally inside your body, or the “injury” is more subtle, like a group of your cells aren’t working correctly together anymore, and it takes time for them to find a new balance. Sometime you have to wait for some cells to divide and for other ones to die to restablish the correct synchronization, which can take a days or weeks.
Typically, when you take a pill, the drugs inside the pill will spread throughout your body in about half an hour, and then they will get to work tweaking the chemical knobs that control different mechanisms in the body. If the mechanism works fast, like nerve furings, you will feel the effects as soon as the drugs have spread.
If the mechanism is slow, like wound healing, you may not see a big difference for days or even weeks.
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