Over-the-counter diphenhydramine, for instance, at least in my country, says adults can take “1 to 2 tablets every 4 to 6 hours.”
If you decide “my symptoms aren’t so bad; I’ll just take one” and then two hours later your symptoms are still bad (or worse), is it safe to take a second tab then? And if you do, should you wait until “4 to 6 hours” after taking the first tablet or the second to take an additional tablet? Does it depend on the drug? (Maybe it’s fine for diphenhydramine but not for ibuprophen?)
I’d imagine blood levels of any particular drug tend to quickly spike and then exponentially decay back to undetectable levels. If you take two tabs, I’d imagine that graph is just twice as tall. If you wait a couple of hours between tabs, it’s got two spikes and the second is a little higher than the first (but not as high as the two-tabs-at-the-same-time spike.)
If the concern is total concentration of drug in the bloodstream at any one point, a second tab a couple hours later is less of a concern than two tabs at the same time. If the concern is total area under the curve, then probably there’s no difference between two tabs at the same time and a couple of hours between. If the concern is total time spent with a blood concentration of such-and-such, I could see there being more concern with taking a second tab just a couple of hours after the first.
And maybe there are other effects that I’m not aware of. Maybe if the blood concentration kicks up to two-tabs-at-once levels, the liver kicks into high gear, clearing the drug out quicker, but if you go a couple of hours between tabs, the liver neve kicks into high gear or some such.
And maybe this question hasn’t even been well studied and maybe there’s not really any good answer. But if there is, I’m curious.
This is a question for a pharmacist. I am not a pharmacist.
DPH is not a 100% safe drug, but looking at how people abuse it with 32+ pills at once, you are at low risk taking one every few hours. It will make you drowsier and it may be unsafe to operate a car because it generally causes a brain fog and poor cognitive function.
If your symptoms are not alleviated by taking one every 4-6 hours, you should be considering an alternative treatment for your issues instead of increasing the dose.
Careful about the survivor bias, there.
You have a point but 28-32 pills or 700-800mg is pretty much the standard abuse amount. It is understood that 1g is where you are at the higher risk of death and 2g is basically suicide. There obviously is risk of organ damage with regular use of higher than therapeutic doses and definite risk of regular use at the higher “recreational” doses. There is some medical findings that any amount of regular use is damaging.
So if we consider 700mg the upper limits of a single dose with low short-term risk, a daily consumption of 200mg over 16 hours(1x25mg every 2 hours) is far safer and still within the recommended dose of 1-2 per 4-6 hours.