meena,

Thanks for your question.  Because you "suddenly" developed this rapid heartbeat, I'm concerned that you might have an abnormal cardiac rhythm, which in some cases, could be caused by the thyroxine.  This is not related to the cholesterol medication.

Though this could be a sinus tachycardia (normal heart beat that is just fast), I suggest you contact your physician and ask to be seen as soon as possible, and be sure to inform him of your symptoms.  There are different types of rapid heart rhythms, some of which are dangerous and require immediate attention.  The only way to tell for sure is to be seen by a physician.   Should you have any chest pain or shortness of breath, I suggest you go to the emergency room.

Best wishes.

Martn Cane, M.D.

I am a little confused as you seem to imply you are taking thyroxine as cholesterol lowering drug when thyroxine is a thyroid replacement hormone (which I take for hypothroidism).

Rapid heartbeat is a common side effect of thyroxine as it is the hormone the body uses to regulate metabolism including heart rate.  Your body converts the thyroxine (T4) to triiodothyronine (T3) which is the biologically active agent.  Since thyroxine has a half-life of about 7 days (i.e. half of it be eliminated from you body every 7 days) you should see its effects wear off after one or two weeks.  However, another possibility is that your thyroid is overactive (hyperthyroidism) and is overproducing T4 and T3 as well.  Even an underactive thyroid can ocassionally "sputter" and produce small bursts that exacerbate the problem.

That being said, there is no way to determine if the thyroxine you are taking is the only cause of your rapid heartbeat without professional testing and diagnosis.  You should always consult a physician regarding changes in your health.

Regards,

HeartHawk