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Is it safe to take a second pill a few hours after the first if the directions say "1 to 2 tablets?" (lemmy.world)

submitted 7 months ago* (last edited 7 months ago) by [email protected] to c/[email protected]

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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.

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[–] [email protected] 3 points 7 months ago

More weight doesn't necessarily mean much more volume of blood compared to someone your height and slimmer.

It's a thing. For example, Americans are presumed being overexposed to drugs compared to 50 years ago because the average weight has gone up 11kg but height remains mostly the same. There's reviews.and.maybe one day refreshes, but it's not really a problem. That ndicates how wide those ranges are for drugs that dose on surface area or weight. The more precise people need to be, the more height, age, metabolism, etc. is factored over weight ballparking.

And then you got OP's over the counter stuff that doesn't even bother with that detail. But it would take someone like me around 300–350 100mg aspirin to get in risk of lethal dose and I'd have stopped noticing improvements afer a small few anyway. In short, without prescription, OP will not be given a quantity of drugs in one packet that could cause any degree of harm or effect—mqybe their bowel movements—if taken all at once. Imagine suicide and murder rates lol.