which is causeing fast heartrate when working out

[wandan89]

Have been on the synthroid for 7 months. Been on the nortryptline for 1 month.
When in gym saw my highest heartbeat on the elliptical read 177. My usual is 160. Few days later tried different machine it read 202 at its highest. Think it just spiked for second. Was not at that rate the whole time. I did not notice it before starting the nortryptline. What med could be causing this?  I did not notice it before starting the nortryptline.

[Carrie Fu, PharmD]

Dear wandan89:

I checked for drug interaction between Synthroid (levothyroxine) and nortriptyline, but there is only minor interaction reported.

However, a potentially life threatening condition called serotonin syndrome may occurred with nortriptyline, either taken alone or with MAOIs (or monoamine oxidase inhibitors) and/or other serotonergic drugs, such as triptans, tricyclic antidepressants, tramadol, and etc.

Serotonin syndrome symptoms may include: tachycardia (or fast heart beat), labile blood pressure, dizziness, flushing, tremor, etc. Since you are also on Synthroid (or levothyroxine), you may experience faster heart rates if the dose is too high for you.

I do not know if your heart rate readings are due to nortriptyline, combination with Synthroid, or something else. However, I strongly recommend for you to consult your provider as soon as possible. You need to get an accurate reading and also find out if there any other underlying medical issue that is causing the high readings.

From your profile, you stated that you get migraine headaches. What medicine do you take for migraine prophylaxis and treatment, any triptans, like sumatriptan (Imitrex) or zolmitriptan (Zomig) and etc?

Please inform your provider(s) and pharmacist of all your medical conditions and medications, including over-the-counter and supplements.

For additional information, please go to:
1. Pamelor (nortriptyline) - FDA
http://www.accessdata.fda.gov/drugsatfda_docs/label/2012/018012s029,018013s061lbl.pdf

2. Nortriptyline - Medline Plus
http://www.nlm.nih.gov/medlineplus/druginfo/meds/a682620.html#side-effects

3. Levothyroxine - Medline Plus
http://www.nlm.nih.gov/medlineplus/druginfo/meds/a682461.html

[wandan89]

Thank you so much. I talked to my Doctor and I have stopped the synthroid and was only on the dose of nortryptline for a month. That has been lowered to 10 mg. Have not mixed in any migraine medicine but I do have imitrex.