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

I have been taking letrozole for 6 months. When I take the full dose I often have abdominal pain, nausea and heartburn...wakes me up in middle of the night. If I take half a dose I have no side effects. My oncologist says there are no studies for the effectiveness of half a dose so he does not support it. He says nausea and heartburn are not side effects of letrozole thus he referred me to a gastroenterologist. I have had several tests and my insides are fine. I am following a GERD diet but still experience digestive issues when I try to go back to full dose of letrozole. May be trying exemestane In the future as it it is the only one I have not been prescribed. My digestive issues were worse on Tamoxifen. Also was diagnosed with gastritis then. Again, could not tolerate full dose of Tamoxifen but did fine with half dose. It is so hard to know the right thing to do. Hoping you get some answers and will stay in touch.

Here is a trial I found that concluded that Lestrozole is effective at 1mg everyday, 2.5 mg every other day, and it is even effective at 0.5 mg. You are probably finished with treatment I hope. But thought I would share it anyway for newcomers like me.

Thank you for your info on manufacturers. Please tell us the info source where you learned Letrozole eliminates lingering breast cancer cells. I thought it was limited to disrupting estrogen.

I will stop my 5 years of letrozole in 8 days. When I first started I was so afraid of side effects I cut pill in half (did not have permission and did not tell the doc until later).

I started 1 whole pill after 3-4 months of spliting pill and then confessed to the doctor. Splitting is NOT recommended per package insert and they “have no data to approve efficacy of a split pill,” but that is water under the bridge now.

I’m surprised that your doc approved the split but I have always wondered if it still works.

I know Letrozole is absorbed in the jejunem where the pH is 4-6, and not in the stomach where the pH is 1-2. Even though the letrozole would have been exposed to an acidic aqueous environment, it is a stable in acid. It is soluble in dicholomethane.

Either way I’ve done 4.9 months of full dose and I’m going to celebrate when I’m done.

I hope you can tolerate the full dose.

I want to thank everyone for their comments. I've taken Letrozole now for almost 3 years, with no major side effects at all. From time to time I have some joint or muscle pain, but with stenosis, sciatica, piriformis issues, and overdoing it with yard work, that may be totally unrelated.
However, I just checked my prescription bottle, and saw that I am on 2.5 mg once every day. I will look into research on this, and discuss the dosage with my oncologist during my next visit.

@ellerbracke I took the full 2.5mg every day for 5 years. My doc was okay with a half dose but I continued on the full dose. I would love info on whether reducing dose even makes a difference in terms of side effects because effectiveness depends on suppressing estrogen, regardless of dose, and that is what causes side effects. So whether 1.25mg or 2.5mg or even 0.5mg I would think the side effects would be the same. But I don't know.

The drug insert for letrozole says that a 20% does of 0.5 mg suppresses estrone and estrone sulfate below detectable levels. This info comes with the medicine and is online.

Even 0.1 mg suppresses estrogen by 75%.
https://www.drugs.com/pro/letrozole.html
The thing is, if estrogen is suppressed, no matter what the dose is, won't side effects be the same?