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Letrozole: When will I start feeling/seeing side effects?

Breast Cancer | Last Active: Apr 17 5:23pm | Replies (127)

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@deluga

How Fast Can Letrozole Side effects appear?
On the third day of taking letrozole, I felt as if an ice-pick had pierced my ear. The pain was excruciating and I stopped. Many painful side effects are still there - pain in ears, jaws, neck, mouth. My oncologist says this can't be caused by letrozole because it takes more than 3 days and the side effects would disappear when I stopped taking it. I've gotten some relief from increasing the meds I take for peripheral neuropathy. Does anyone have any information on how long it takes for letrozole side effects to appear? Any scientific studies too?
Thanks for any information.

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Replies to "How Fast Can Letrozole Side effects appear? On the third day of taking letrozole, I felt..."

@deluga, I moved your message to this existing discussion:
- Letrozole: When will I start feeling/seeing side effects? https://connect.mayoclinic.org/discussion/letrozole/

I did this so you can read the experience of others and connect with members taking Letrozole.

Like all medicines, letrozole can cause side effects, although not everyone gets them. And how long it takes for side effects to appear is different for every person.

Common side effects of Letrozole mimic menopause symptoms and include hot flushes, difficulty sleeping, tiredness and low mood. Side effects usually improve after a few months as your body gets used to the medicine.

The side effects that you're experiencing sound rare and potentially not related to Letrozole or something that is very unique to you. Perhaps a drug interaction with another drug you're taking. There is also something called ototoxicity - hearing or balance problems due to a medicine. This can happen when someone is on a high dose of a drug that treats cancer, infections, or other illnesses. Might be worth talking to your pharmacist.

What medication are you taking for peripheral neuropathy? Did you increase the dosage under the guidance of your doctor or pharmacist?

I took Letrozole for 18 weeks. I had body and muscle aches, developed carpel tunnel in both hands, trigger finger and thumbs in both hands. I can't remember how quickly the side effects came on. My oncologist was not convinced it was the medication. I took a break suggested by my oncologist. I have been off any AI's since May 2022 and the last symptom, the trigger thumbs are finally going away. I have decided not to go back on any AI's for now. My oncologist would like me to take exemestane, but I am going to put my energy toward diet, supplements and exercise. I am 70 this December and quality of life is important to me. I had a double mastectomy, no reconstruction and no lymph involvement.

I also had increased neuropathy issues (I have hereditary neuropathy with pressure palsies HNPP) when I started taking letrozole; however, I started taking kisqali at the same time so it's hard to say which med caused which side effect. I've been on both for two years so I don't remember if it was immediate or if there was a slight delay, but most side effects started pretty quickly I believe. My increase was to shooting pains in my feet mostly, but also legs and other random places. Mostly when resting. Best of luck to you.