Why do our bodies build up a tolerance to some medications but not others?
In: Biology
One way some drugs work is by either blocking or boosting a signal in your brain or other part of your body. Much of your body works by cells releasing a chemical and another cell receiving that chemical and reacting to it (maybe a nerve sending a pain signal or your stomach creating acid) and then a third cell reabsorbs that chemical to stop the process. Drugs can “pretend” to be that chemical – so the those receiving cells start reacting, the drugs can block the cells that absorb the chemical making your natural chemicals last longer, or the drug can block the cell that’s receiving the chemical – stopping the reaction.
If a drug blocks the receiving cell from “sensing” the chemical, your body might continue to create the chemical. Alcohol does this. Your body will adopt to chronic use of the drug by creating more of the chemicals to compensate. your body can actual overdose on it’s naturally occurring chemicals if you remove the blocking drug suddenly.
If a drug mimics a chemical in your system, your body may respond by not bothering to make it’s own version of the chemical. Since you don’t have the naturally occurring chemical, you will need more to get the same effect. The same is true with blocking the reuptake of the chemical.
Your body can’t always make more of these chemicals. If that is the case, you won’t develop a tolerance or a dependency (generally) since your body doesn’t adjust.
There are other factors as well. Some of your organs (like your liver) can actually grow to filter more.
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