Atenolol when starting Methimazole?

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Jayne & Sweety

Jayne & Sweety

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Took my mother's cat to a new vet I was trying out as I suspected diabetes or hyperthroidism since she has gotten so thin - 5 lbs. It turned out to be HyperT and the vet started her on the Methimazole with 6.25 mg/daily of Atenolol for two weeks. I know what it is, and does but the vet never did a blood pressure check, or ultrasound. He just said her heart was beating really fast, and that he didn't hear any murmurs which was good. But she's never been to the vet (16 years old) so she was quite stressed. Surprisingly, her BG was only 69.
My question is - what IF she doesn't need the Atenolol? What could happen, and how fast? Low blood pressure? Death? What should we look for, and do you think it was necassary and worth any risks?
 
Hi

Some vets do start hyperthyroid cats with very high heart rates on atenolol and methimazole, and wean off the atenolol as the hyperthyroidism is controlled. The assumption is that the high HR was not due solely to stress, but to the hyperthyroidism. Hyperthyroidism can cause a cat to become so tachycardic (fast heart rate) that the heart becomes less efficient -- it's beating too fast to fill up with enough blood. (I saw a cat once with a HR of 290-310bpm! That was an emergency, and she was started on IV drugs to slow her heart rate.)

Atenolol can cause lethargy and it can cause the heart to beat too slowly. Not so slowly that they die, but slow enough that they may feel weak. If you are able to take the cat's HR at home, that would be very helpful. Take it when the cat is relaxed. If you dont' have a stethoscope, you can try to feel the heart beat in the chest, between the legs, or feel the femoral pulse in the inside thigh (there is probably a how-to on the internet somewhere). Don't take pulses using your thumb, BTW, since your thumb has its own pulse and things get confusing!
 
Thanks Jess! You are such a lifesaver around here!
She's only going to be on it for two weeks - but I am much relieved that she can't die. I will try to get a pulse.

Thanks again!
 
Sorry, one more thing -- this is a cat at high risk for having hypertension, so make sure they do a BP when she rechecks. The drug of choice for hypertension is amlodipine.
 
But the hypertension should be taken care of with the control of the hyperthyroidism, right? He said the Atenolol was for "just in case" and didn't want her to throw a clot.

Thanks again, and we will have her BP checked. Her sodium was high, but in range. Can't the BP be raised because of the stress?
How can they ever tell the real BP with cats, they all get so stressed...
 
Jayne & Sweety said:
But the hypertension should be taken care of with the control of the hyperthyroidism, right?
Click to expand...

Well, two things: one, maybe it is not wholly related to the hyperthyroidism. Two, it may take some time to regulate her on the methimazole and in the meantime she'd have the blood pounding her kidneys and eyes (and other organs). It's worth treating.

[quoteCan't the BP be raised because of the stress?
How can they ever tell the real BP with cats, they all get so stressed...[/quote]

Yes, it can, although I've taken the BP of some pretty PO'd cats who were still in normal range. Average for a cat is probably 110-130; if you get a 160-170, you think about the stress factor. If you get a 200-220+ , you reach for the Norvasc :-)
 
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