How can medications with very short half lives (~2 hours) ever be effective given that a non-negligible steady state is never achieved unless dosed like 6 times/day?

Question

There are some medications, like buspirone, that have a very short half-life of 2-3 hours. Even if you took it twice a day, you’d only end up achieving a steady state of about 3-5% of the original dose. It’s very easy to do the math on Excel: [here’s an example of a 2 hour half-life medication taken twice a day](https://i.imgur.com/2N7HbmT.png).

One possible solution is taking the medication a ridiculous number of times per day, which is simply not going to happen (it’s hard enough to get daily compliance out of patients).

A second possible solution is prescribing a dose that’s like 10-50x larger than the desired steady-state level. For example, let’s say taking 100mg (2x/daily) of a medication provides a steady state of about 1-3% of that dose (as is approximately the case for a 2x/daily medication with a ~2 hour half life). If the *desired* steady state is 75% of that dose, you could achieve that steady-state by instead prescribing **2500mg** 2x/daily.

The problem with that, I assume, is that a 25x larger dose of almost *any* medication would have intolerable side effects.

But obviously these medications are approved, prescribed, used, and apparently actually do work. **But how?** I just don’t see how it’s possible. I’m sure I’m just missing something.

In: Biology

Answer 1

I heard some pills are designed to release the active drug at a controlled rate. Which apparently is why two brands with the same drug and dose may work differently.