1. < Heart Rhythm Conditions
Profile picture for carbcounter

Atenolol pills seem to vary on actual dosage

Posted by carbcounter @carbcounter, Oct 24, 2025

Has anyone had the experience of taking beta blockers, with some success, but then finding that sometimes it's like maybe you get a bad pill that has 2x or 10x the dosage it should?

I was prescribed atenolol OMG about 25 years ago for a combination of blood pressure and some minor and generally unspecified heart arrhythmias. They seemed to help. Took them for many years, no real problem. And a tiny dose! I was prescribed a low dose, 25mg twice a day - but when I took the very first 25mg tablet it felt like I'd been hit by a brick, my heart rhythm no longer responded to exercise - so I got permission to cut it back to half (an already tiny) 25mg tablet, per day! And that worked well for me. After some years I raised it to half a tablet twice a day.

But a couple of years ago I had an experience that it seemed to slow my pulse rate TOO much. I started breaking the tablets into even smaller pieces and that seemed to help. Going without, did not seem effective, so it did not seem it was my own metabolic baseline that hand changed. I thought about talking to pharmacist or doctor - but did neither.

Anyway, that passed, and didn't have the issue again - until today. And maybe more strongly than ever. Pulse rate a little low but super-resistant to change by exertion. Could this be dangerous? Well, if the pill variation was maybe 2x the proper dosage it should be mostly harmless, but if it's much greater than that I don't know.

So I'm just asking if anyone might have had any similar experiences or any suggestions under the circumstances. Thanks.

Interested in more discussions like this? Go to the Heart Rhythm Conditions Support Group.

Profile picture for Sue, Volunteer Mentor
Mentor
Sue, Volunteer Mentor | @sueinmn | Jul 25 12:10pm
In reply to @rushhome "Not atenolol but I kept getting good and bad reactions to the generics on synthroid. Asked..." + (show)
Profile picture for rushhome @rushhome

Not atenolol but I kept getting good and bad reactions to the generics on synthroid. Asked my pharmacist and he said the law says generics can fluctuate 10% up or down, meaning sometimes you get less than prescribed sometimes more. If the mfgr. changes the swing can be 20% in one crack. I had dr. write prescription as 'AS Prescribed' no generics. I now get it direct from Abbie as buying it from my pharmacy is too expensive and they have a direct cost of 75.00 per 3 months instead of 150.00.

Jump to this post

@rushhome
You said "Asked my pharmacist and he said the law says generics can fluctuate 10% up or down, meaning sometimes you get less than prescribed sometimes more..." This is sort of correct, but it applies to all drugs. Imported drugs were tested before allowing into the US market in the past, but not sure if it is still being done routinely.
Once a drug is on the market, whether brand name or generic, US manufactured or imported, testing is random and very infrequent.

Pills and capsules are individually tested in lots of 10, and if there are any "outliers" - variability +/- 15% - larger quantities must be tested. Those with variability of +/- 10% pass.

REPLY
1 reply
Profile picture for rushhome
rushhome | @rushhome | Jul 25 4:07pm
In reply to @sueinmn "@rushhome You said "Asked my pharmacist and he said the law says generics can fluctuate 10%..." + (show)
Profile picture for Sue, Volunteer Mentor @sueinmn

@rushhome
You said "Asked my pharmacist and he said the law says generics can fluctuate 10% up or down, meaning sometimes you get less than prescribed sometimes more..." This is sort of correct, but it applies to all drugs. Imported drugs were tested before allowing into the US market in the past, but not sure if it is still being done routinely.
Once a drug is on the market, whether brand name or generic, US manufactured or imported, testing is random and very infrequent.

Pills and capsules are individually tested in lots of 10, and if there are any "outliers" - variability +/- 15% - larger quantities must be tested. Those with variability of +/- 10% pass.

Jump to this post

@sueinmn Thanks for the clarification! I have been on the brand name now for about 2 years and my numbers stay nice and steady when tested, so happy to pay the difference from the 2.00 generic. My pharmacist told me I am almost at a microdose where the variations would be more dramatic.

REPLY
Profile picture for sunshine3657
sunshine3657 | @sunshine3657 | Sep 18 4:10pm

I took Nifedipine 60 Extended release plus Atenelol 25 mg for about 25 years. Now I am 78 and the Nifedipine 60was not maintaining my blood pressure. It seemed to stop several hours before PM dose. Blood pressure started to get wild. I ended up in ER with 189/113 Pulse 103.
Blood pressure meds changed to:
Atenelol 25 mg, Lorsatan 50 AM
Also
Amolodine 10 mg PM.
Finally blood pressure near normal after 6 days on new meds.
BUT when I take the Atenelol 25 in AM, I am very quickly out of breath, noticably.Pulse appears ok but short of breath. Told to use an inhaler, inhalers with Atenelol 25 are not supposed to be used together. Need to stop the shortness of breath and its obvious its the Beta-blocker. Maybe go to 12.5mg if Primary agrees?

REPLY
1 reply
Profile picture for sunshine3657
sunshine3657 | @sunshine3657 | Sep 18 4:14pm
In reply to @californiazebra "Well maybe atenolol was why it was so hard to get my heart rate up high..." + (show)
Profile picture for Zebra @californiazebra

Well maybe atenolol was why it was so hard to get my heart rate up high enough during a stress test.

I’m trying to get off atenolol because my BP and heart rate are too low after adding cancer meds but I can’t seem to successfully wean off without rebound issues. I’m now down to 6 mg every other day but even on that ridiculously low dose at 2.5 days off I’ll have tachycardia so then I take my 6 mg and it’s gone in an hour. I can’t cut that tiny pill up any smaller. The cardiologist thinks it should be no trouble to stop at even a higher dose but my body is so sensitive to meds it’s just not working out. I’ll keep trying to space the dose out farther. Best of luck to you. Meds can be so frustrating and different for everyone.

Jump to this post

I Agree, tapering off is the hardest thing to do. I am so sensitive, if it fixes one thing it messes up another. Good luck.

REPLY
1 reply
Profile picture for Zebra
Zebra | @californiazebra | Sep 18 5:16pm
In reply to @sunshine3657 "I Agree, tapering off is the hardest thing to do. I am so sensitive, if it..." + (show)
Profile picture for sunshine3657 @sunshine3657

I Agree, tapering off is the hardest thing to do. I am so sensitive, if it fixes one thing it messes up another. Good luck.

Jump to this post

@sunshine3657
So I finally got off atenolol a few weeks ago. How? Since I had rebound stopping just 6 mg, I took a knife and chopped my pills to bits. I looked at the 6 mg (1/4 pill) and picked out smaller bits estimating 5, 4, 3, 2, 1 mg. I used those to gradually taper down over the next 3 weeks. Success! No usual tachycardia rebound after 60 hours. Everything was great for a week and BP and HR went right back up to the normal range. Great!

The bad news. Kisqali (cancer med) caused my afib. 5 long episodes a month for nearly 5 years. I stopped Kisqali and episodes immediately dropped to 1 per month for a year. A week after stopping atenolol suddenly I started going into afib once or twice a week with no identifiable trigger. Pattern has changed to a variable number of hours (23-38 vs 40-65 before), higher heart rate during (170 vs 150), an even more chaotic pattern, and tachycardia for a few hours after afib stops, BP not dropping as low. Oops! So not total success after all unless this is a temporary form of rebound.

My neuro issues have done well with the wean off plan. No rebound there. Yay!

I will have a pulsed field ablation before the end of the year (waiting for a date) so I want my BP and HR to be normal and don’t want atenolol masking anything during the ablation. I’m not starting atenolol again, but it may be a long 2-3 months before the ablation if the afib doesn’t slow down. It’s been a long 6 years with this annoying afib.

Good luck to others. I had my cardiologist’s blessing to stop atenolol. Be sure you do to be safe. Not sure I’m totally safe but I’m on Eliquis and will power through. ❤️

REPLY
Profile picture for carbcounter
carbcounter | @carbcounter | Sep 18 6:58pm
In reply to @sunshine3657 "I took Nifedipine 60 Extended release plus Atenelol 25 mg for about 25 years. Now I..." + (show)
Profile picture for sunshine3657 @sunshine3657

I took Nifedipine 60 Extended release plus Atenelol 25 mg for about 25 years. Now I am 78 and the Nifedipine 60was not maintaining my blood pressure. It seemed to stop several hours before PM dose. Blood pressure started to get wild. I ended up in ER with 189/113 Pulse 103.
Blood pressure meds changed to:
Atenelol 25 mg, Lorsatan 50 AM
Also
Amolodine 10 mg PM.
Finally blood pressure near normal after 6 days on new meds.
BUT when I take the Atenelol 25 in AM, I am very quickly out of breath, noticably.Pulse appears ok but short of breath. Told to use an inhaler, inhalers with Atenelol 25 are not supposed to be used together. Need to stop the shortness of breath and its obvious its the Beta-blocker. Maybe go to 12.5mg if Primary agrees?

Jump to this post

@sunshine3657
For me, as I said in the opening message, 25 atenolol was too much for me - at least at first. And it was supposed to be twice a day, which I couldn't imagine.

BUT: amlodipine!!!? I took that in combination and then separately for a couple of years. It wasn't doing the job and I felt worse and worse, zombied out. It's a very common drug but it is not rare to hear people have trouble with it. I stopped - and it takes a week or so to clear, though it's not one that has stopping problems other than that. I felt MUCH better. I tried a smaller dose recently, it also didn't help so I dropped it again.

If you can clear it with your doctor I'd suggest trying to drop the amlodipine and restarting the atenolol.

For the arrhythmias - have you reviewed your diet (and supplements) for all vitamins? I suffered horrible arrhythmias for several years, doctors no help at all, but I started taking a simple multivitamin to cover all bases and also just one or two "baby carrots" once or twice a day for vitamin A (and beta carotene). And my arrhythmias cleared 99% within a few weeks. That's my story, fwiw.

REPLY
Please sign in or register to post a reply.