If you’ve been prescribed letrozole (Femara) to help prevent your breast cancer from returning, it’s good to be aware of all potential side effects. Insomnia (persistent trouble sleeping) is one side effect that several MyBCTeam members have reported experiencing while taking letrozole.

One member asked, “I’ve been taking letrozole in the evening, and now I have insomnia. Does anyone take it in the morning? Do you sleep well?”

In this article, we’ll explore the ways that letrozole may contribute to sleep problems — either directly or indirectly through disruptive side effects — and we’ll provide insights on managing this issue.

Letrozole Can Interfere With Sleep

Letrozole and other medications used in hormonal therapy can interfere with your sleep patterns. This can lead to insomnia — a sleep disorder that causes difficulty falling or staying asleep.

In one clinical trial of letrozole, 7.8 percent of participants taking letrozole — all postmenopausal women with HR-positive and node-positive early-stage breast cancer — reported insomnia as a side effect. By comparison, 7.2 percent of people in the trial who took anastrozole also reported experiencing insomnia.

Side Effects of Letrozole That Can Disrupt Sleep

In addition to disrupting your sleep patterns directly, letrozole has some other potential side effects that can make sleeping more difficult. These side effects include:

• Pain — Letrozole can cause pain throughout your body, which may make both finding a comfortable sleep position and falling asleep difficult.
• Urinary problems — Letrozole may make you urinate more frequently, which can wake you up in the middle of the night.
• Hot flashes — Letrozole can interfere with your body’s ability to regulate its temperature, which can cause night sweats that wake you up at night.
• Depression and nervousness — Letrozole can impact your mental health, making it hard to relax at night.
• Cough — Frequent coughing can make it difficult to fall asleep or may wake you up in the night.
• Dizziness or lightheadedness — These symptoms may make it harder to relax or move safely when getting into or out of bed.
• Nausea — Feeling like you’re going to vomit can be incredibly disruptive to sleep.

Letrozole may also cause you to have troubled breathing. Difficulty breathing can cause anxiety and disturb your sleep.

However, if this side effect comes on suddenly, is severe or occurs with chest pain, you should contact a healthcare provider immediately, as it may be a sign of a more serious problem.

Managing Sleep Disturbances

A lack of sleep can have far-reaching impacts on your health and quality of life. There are several strategies that you can use to cope with your insomnia.

Create a Sleep Routine

Establishing a consistent sleep routine can improve your sleep quality. Going to bed at the same time every night helps regulate your body’s internal clock and promotes a natural sleep-wake cycle.

To optimize your sleep environment, ensure your bedroom is dark, cool, and quiet. Consider:

• Using blackout curtains
• Adjusting the temperature
• Minimizing external noises

Playing white noise or calming sounds, like a gentle river, has also been found to help people sleep.

Avoid screens, such as smartphones or laptops, before bedtime, as the blue light they emit can interfere with sleep. Instead, engage in calming activities like yoga, deep breathing exercises, or reading to unwind and prepare your body for a restful night’s sleep.

Avoid napping or sleeping during the day, as it can disrupt your sleep pattern. If you’re having trouble falling asleep, refrain from lying in bed for more than 20 minutes. Instead, engage in relaxing activities like reading or listening to soft music until you feel drowsy.

Find the Right Sleep Aid

If you’re struggling with persistent insomnia, you may consider adding sleep aids to your treatment plan. There are various types of sleep aids available, including over-the-counter sleep aids, prescription medications, and natural supplements like melatonin.

Be aware of potential risks associated with sleep aids, including:

• Next-day drowsiness
• Disrupted sleep stages
• Dizziness
• Falls
• Confusion
• Uncertain safety of some supplements

Always consult with your healthcare provider before starting any new medication or supplement, as these drugs could interfere with how letrozole or other medications work or worsen other side effects. Your doctor can help you choose a safe sleep aid.

Make Exercise a Priority

Regular physical activity, based on your health and abilities and approved by your cancer care team, can be an effective way to help reduce insomnia. Engaging in regular physical activity can provide numerous benefits in addition to helping you sleep.

Exercise can boost your daytime energy, helping you feel less tired during the day and sleep better at night. It also helps reduce stress and anxiety, which are common causes of sleep disturbances.

Research has also linked engaging in regular physical activity with better survival rates and lower chances of recurrence in women diagnosed with high-risk breast cancer, according to the National Cancer Institute.

Find Ways To Cope With Night Sweats

Coping with night sweats — another potential side effect of letrozole — can be challenging, but there are several techniques that can help provide relief.

Keep Cool

One effective strategy is to use cooling techniques such as:

• Setting your thermostat lower at night
• Opting for lightweight bedding and sleepwear
• Using fans
• Trying cooling bedding
• Wearing lightweight or loose-fitting clothing

One MyBCTeam member said of their cooling blanket, “I call it my magic blanket — it’s about 10 degrees cooler on one side than the other.”

Sleep on a Towel

Another helpful tip is to sleep on a towel or moisture-wicking blanket, which can absorb excess moisture and help you stay dry throughout the night. You can also easily refresh your bed if you wake up sweaty by changing out the towel.

Take a Shower

If you wake up drenched in sweat, a quick shower can help cool you down and make falling back to sleep easier.

Treat Hot Flashes

Your doctor may add medications to help treat hot flashes. One MyBCTeam member reported improvements in hot flashes while taking the antidepressant venlafaxine (Effexor).

“The first month on letrozole, I had hot flashes once or twice a day, but mostly at night. After a month, they gradually stopped, and within two months I rarely had them,” the MyBCTeam member said. “I also started taking Effexor for anxiety about two weeks before starting letrozole. My oncologist mentioned that Effexor helps lessen hot flashes.”

Talk With Your Healthcare Providers

If you’ve tried managing your insomnia yourself and can’t seem to find relief, it’s probably time to talk with your doctor. They may recommend taking letrozole at a different time of day or discuss other ways to manage the insomnia.

“I take letrozole first thing in the morning,” said one MyBCTeam member. “I had to do that so I could sleep. It made a big difference.”

Always get medical advice before making any changes to the way you take your medications.

Join the Conversation

On MyBCTeam, people share their experiences with breast cancer, get advice, and find support from others who understand.

Have you experienced insomnia while taking letrozole? Let others know in the comments below.