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Medicine and half-lives

I don't always take pain medication But when i do, I take more ...

People are often wondering why they need to keep taking their medication or why something hasn't worked yet or if they need more than what they've already taken so I just wanted to go over the broad strokes around that.  I will try to do some follow up topics too.

Anything you put in your body, it tries to get rid of.  It is used as best able by your body and the body then tries to spit out all the garbage that's leftover.  That's the reason for why you go to the bathroom and why we die when we stop eating.

The same is true for all medications.  Talking mostly about pills, any medications put into your body take about 30-60 minutes to get through your stomach and to your small intestine where it's absorbed.  There are some medications you need to take by themselves or in relation to meals or without other medications because there can be interference with how stomach acid affects them and how they are absorbed in the intestine.

Once a medication gets into your system, your body starts trying to get rid of it using the kidneys and/or liver.  That's why for many things you need to keep taking the medication.

How often and how much of a medication you have to take depends mostly on it's half-life, which is the amount of time your body takes to reduce the medication concentration by half.  A rule of thumb is that it takes about 4-5 half-lives for a medication to reach a steady state.

As a for-instance, Synthroid (levothyroxine) is for people with low or non-existent natural thyroid hormone levels.  It's half life is 6-7 days, so when there's a dose change, it takes 4-5 weeks for the medication to reach a steady level.  For that reason, while we typically have people take it daily, you can theoretically take a week's dose all at once and it would work out the same, although initially can make people feel a little jittery for a day or two.

On the other side of things, ibuprofen has a half life of 90-120 minutes so it needs to be taken more frequently to reach a steady state, often three times per day.  There's a little piece about this here with a nice graphic.

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