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Old 04-21-2004, 11:00 PM   #1
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hottoddy HB User
Antihistamines Raise Blood Pressure?

I used to think that only decongestants raise blood pressure, but have also come across conflicting information about antihistamines. The theory is that histamines cause blood vessel dialation (established), and antihistamines have the opposite reaction. Or do they just contra the histamine effect and go no further? As an allergy sufferer with borderline high bp, I'm wondering if antihistamine usage could be making things worse.

Last edited by hottoddy; 04-21-2004 at 11:01 PM.

Old 04-22-2004, 03:36 PM   #2
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Re: Antihistamines Raise Blood Pressure?

It's not likely that the nonsedating antihistamines would raise your BP -- don't know about the "old line" antihistamines. However, I do notice that the Zyrtec mongraph lists hypertension as emerging in up to 2% of patients in trials for the drug, although there was no proof that the Zyrtec was the cause. But you never know -- I've certainly had a few very atypical side effects from some meds.

Why not just take the antihistamine and keep close tabs on your bp? Discontinue if there seems to be an adverse effect, and maybe re-challenge (try it again after awhile) to prove that it was really the antihistamine that was behind the temporary BP increase.

But again, you're unlikely to have a problem in the first place. I have mildly elevated BP (I take Benicar for it), and haven't noticed any BP-raising effect from Allegra, Claritin or Astelin.


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Old 04-24-2004, 12:57 AM   #3
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Re: Antihistamines Raise Blood Pressure?

Thanks. I'm trying to see if there's any specific BP reaction. The problem is my BP tends to bounce around a lot, so it's hard to determine if any one thing is affecting it. Also, my BP tends to be higher on bad allergy days regardless. It seems safe to say that antihistimines aren't making the situation worse, but I'll continue to monitor it.

Old 04-25-2004, 10:37 AM   #4
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Re: Antihistamines Raise Blood Pressure?

I hear ya about the bouncing BP. Now, I assume since you're so tuned in to your BP (generally a good thing), you are trying to watch your weight and sodium intake (if your BP is salt sensitive), possibly taking BP med(s), and hopefully exercising (my personal shortfall, although 40mg of no-side-effect Benicar + attention to weight are keeping it at an average of 113/72). If by some chance you're not doing any of the above, I'm sure that's all more significant than whether or not you're taking an antihistamine.

The kind of monitoring you suggest sounds fine. But if "bounce" is a major issue and you REALLY want to try nailing down potential effects, how about this: Go for two weeks without the antihistimine. During this tme, measure your BP at, say, 7AM and 7 PM every day. With each reading, make a note of whether it's a bad allergy day or not. Then do the same thing taking the antihistamine daily for two weeks (even if you normally only take it as-needed). Then take the "Good Allergy Days" and calculate and comapre the average readings between the pre-antihistamine and post-antihistamine periods and see if there's a meaningful increase. Then do the same thing for the "Bad Allergy Day""pre" and "post" averages. Doing it this way helps get around the two counfounding isssues of BP bounce and the tendency for your BP to naurally increase on bad allergy days.

Of course, this all assumes that you don't mind suffering through the untreated allergy symptoms during the no-antihistamine test period!

Again, this is proably all overkill unless you just can't get a sense of whether the antihistamines could be having an effect.


Old 04-25-2004, 11:12 AM   #5
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Re: Antihistamines Raise Blood Pressure?

I checked your posting history and saw your post about the large variability in your BP measurements over short periods of time and between arms. First, systolic BP can easily change 20 or even 30 points in a matter of 10 minutes, even in a nonhypertensive person. This is documented, and that's why it's hard to understand why doctors -- even top hypertension specialists -- only check once (or once in each postion -- sitting, tilted, lying). I have a friend who has similar swings, and sometimes sees differences of easily 10 points systolic -- and sometimes up to 20 -- between arms. Of course, there is always the possibility of anxiety, but I don't get the sense that that's what going on with you. You might be interested in the following pdf link from the Journal of Hypertension. The general topic is the need to re-evaluate current BP measurement techniques, and at one point they discuss the issue of how cuff readings between arms can be up to 20 mg different (if it's higher than that they suggest tests): [Caution: Lengthy Document]

Last edited by RickRick; 04-26-2004 at 12:32 AM. Reason: Clarification

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