Trelstar: What to Expect, Side Effects, and More

Trelstar (chemical name: triptorelin) is approved by the U.S. Food and Drug Administration for the treatment of prostate cancer. However, the medicine is sometimes used to treat women who have been diagnosed with early-stage, hormone-receptor-positive breast cancer. 

The medicine is prescribed to women who have had surgery to remove the cancer, haven’t gone through menopause, or have been told the cancer has a high risk of coming back (also called recurrence). 

Trelstar is a type of hormonal therapy called a LHRH (luteinizing hormone-releasing hormone) agent antagonist. LHRH antagonists shut down the ovaries and stop them from producing estrogen so there is less estrogen to fuel the growth of hormone receptor-positive breast cancer.

Zoladex and Lupron are also LHRHs; like Trelstar, they contain a synthetic version of LHRH. 

Trelstar is given as an injection once a month.

Trelstar is often used in combination with Tamoxifen or aromatase-inhibitor drugs like anastrozole, letrozole, and exemestane.

Like almost all breast cancer medicines, Trelstar can cause side effects, some of them severe.

The most common side effects of Trelstar are:

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  hot flashes

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  mood swings

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  loss of libido

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  osteoporosis

Members of our community discuss their experiences with Trelstar in the community forum. Here are some of their comments. Remember, it's essential to talk to your doctor about any side effects you're having and ask about ways to manage them.

“I'm on monthly shots of triptorelin and, since the estrogen helps to maintain body temperature and increases blood supply to the skin, I think that's the reason for my ‘cold flashes.’” —Yaguarete

Read more in our Trelstar discussion forum.

The cost of Trelstar may vary. The price you’ll pay depends on the drug manufacturer, your health insurance provider and plan, where you live, and the pharmacy you use. 

Note: Your insurance company may require you to get prior authorization before covering Trelstar. 

Learn more about financial assistance and medicine cost-lowering tips.