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Notes -
Antihistamines. Do they reduce IQ?
Yes. The sad thing about the majority of pharmaceuticals in use today is that they're blunt instruments, hammers substituted for scalpels. Histamine, while we're mostly accustomed to encountering its effects from annoyances like hives or allergies, also functions as a neurotransmitter in the brain. It happens to modulate arousal and awakening in the brain, which is why sedation is/was a common side effect of antihistamines (more so in the older ones).
https://pubmed.ncbi.nlm.nih.gov/10856168/#:~:text=In%20a%20recent%20comparative%20trial,memory%2C%20vigilance%2C%20and%20speed.
The second-generation antihistamines are classified as "non-sedating", which is more or less correct, even if a few of them do have mild sedative effect, at least they're much better in that regard than the OGs. Keep in mind you're not thinking your best when you've got a reason to take them, such as during allergies or a cold.
I don't see any suggestion that the effect persists indefinitely, at least not for acute use at recommended doses, and you can avoid the worst of it by getting the better ones from the non-sedating class.
Is daily cetirizine use significantly hazardous?
My memory says no, but I did look it up and there doesn't seem to be any claims of it being hazardous beyond the mild sedation itself.
Thanks!
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Related followup: what is the safest OTC sleep aid? Thoughts on doxylamine (unisom)?
with cycling it is fine only when you have cycleways separated from roads without real pedestrian/cycling traffic on them
falling under car while on bicycle is a poor idea
definitely makes sense, more than what I expected to be reasoning (that on bicycle hitting others will cause much lesser harm), thanks for clarifying
(I have quite limited experience with car driving)
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You said safest, not the most effective, so I'm going to go with a glass of cold milk haha.
Truth be told, there isn't much in the way of good, almost perfectly safe choices, at least in OTC drugs that I'm aware of, and availability might well be in different in the States from what I'm used to. I could vaguely recommend l-theanine as a highly safe anxiolytic, even if it's not a sedative. Melatonin is highly dubious in terms of usefulness. But if you want to be knocked the fuck out, older antihistamines are your friend.
I don't have a particularly strong opinion on doxylamine beyond my theoretical knowledge, it's not the antihistamine used regularly where I hail from, but used in moderation? Doesn't seem all that bad. But it will almost certainly have the cognitive effects I mentioned above.
Just did some reading of actual studies. E.g. this meta-analysis from NCBI:
Why should I find this plausible, rather than making the standard "correlation is not causation" point? Surely people with issues sleeping are in general less healthy, physically and/or psychologically. I don't see anything in there to indicate they controlled for anything.
Some references also seem to do nothing more than ask if people took any sleep aid, lumping together everything from melatonin (presumably very safe, maybe placebo) to daily benzos (clearly neither very safe nor a placebo).
Edit: I am bad at reading (maybe it's the doxylamine). They did control for things. But my question re causation stands. I feel like TheMotte is usually very skeptical, and I find myself surprised by the strength of multiple posters' convictions here.
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Fascinating that you say melatonin is dubious in usefulness. I swear by my 300 micrograms a day (dosage at Scott's recommendation).
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I've been taking Claritin (loratadine) but I still feel like I'm losing some bandwidth. I can't hold as many things on my mind as I usually do. Too bad it's either this or hives for now.
Levocetirizine is a non-sedating one that causes minimal cognitive effects, I'd recommend it. The paper I linked has examples of some others that couldn't be disentangled from placebo, so hopefully you find one that works for you.
Or you could go for a topical preparation? That should have fewer cognitive side effects.
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(Original) Benadryl is also an anticholinergic, and "Anticholinergic use later in life is associated with an increased risk for cognitive decline and dementia among older people."
I don't recall reading about any indications of problems from other antihistamines, but then again I only happened across this one by chance, years ago; I'm not an MD or pharmacist. Many antihistamines have drowsiness as a side effect, and that always makes me a bit suspicious.
Is "causing drowsiness" inherently an indicator of long-term negative cognitive effects?
Inherently? Surely not. This is just a vague heuristic, and I'd be shocked if it was actually a universal rule. It just seems that there are some pathways to "make brain quiet down now" that don't do so perfectly gently, which a priori isn't too surprising. General anesthesia and alcohol are the two other examples that come readily to mind. So when I see a new drug that has that effect, and there's no safe explanation (like for melatonin) apparent, I wonder if it's doing so unsafely.
I don't worry too much though. I've had general anesthesia once, and I wouldn't hesitate to take Benadryl after an allergic reaction, because I doubt the costs outweigh the benefits, and I had a glass of wine with dinner tonight, because YOLO.
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Is there evidence they do?
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