Letrozole / Ribociclib Side Effects

Medically reviewed by Drugs.com. Last updated on Jan 29, 2025.

Applies to letrozole / ribociclib: oral tablet.

Precautions

It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly. Blood tests may be needed to check for unwanted effects.

It is unlikely that a postmenopausal woman may become pregnant. But, using this medicine while you are pregnant can harm your unborn baby. If you are a woman who can bear children, your doctor may give you a pregnancy test before you start using this medicine to make sure you are not pregnant. Use an effective form of birth control to keep from getting pregnant during treatment and for at least 3 weeks after your last dose. If you think you have become pregnant while using the medicine, tell your doctor right away.

If you plan to have children, talk with your doctor before using this medicine. Some men and women using this medicine have become infertile (unable to have children).

Interstitial lung disease or pneumonitis can occur while using this medicine. This can be life-threatening and requires immediate medical attention. Check with your doctor right away if you have chest pain, cough, difficulty with breathing, fever or chills.

Serious skin reactions, including Stevens-Johnson Syndrome, toxic epidermal necrolysis, or drug reaction with eosinophilia and systemic symptoms (DRESS) can occur with this medicine. Check with your doctor right away if you have black, tarry stools, blistering, peeling, or loosening of the skin, chest pain, chills, cough, fever, painful or difficult urination, red skin lesions, sore throat, sores, ulcers, or white spots on the lips or in the mouth, swollen glands, unusual bleeding or bruising, or unusual tiredness or weakness with this medicine.

Contact your doctor right away if you have any changes to your heart rhythm. You might feel dizzy or faint, or you might have a fast, pounding, or uneven heartbeat. Make sure your doctor knows if you or anyone in your family has ever had a heart rhythm problem including QT prolongation.

Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellow eyes or skin. These could be symptoms of a serious liver problem.

Ribociclib and letrozole combination can temporarily lower the number of some types of blood cells in your blood. Because of this, you may bleed or get infections more easily. To help with these problems, avoid being near people who are sick or have infections. Wash your hands often. Stay away from rough sports or other situations where you could be bruised, cut, or injured. Brush and floss your teeth gently. Be careful when using sharp objects, including razors and fingernail clippers.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal (eg, St. John's wort) or vitamin supplements.

Serious side effects

Along with its needed effects, letrozole / ribociclib may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking letrozole / ribociclib:

Other side effects

Some side effects of letrozole / ribociclib may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

For healthcare professionals

Applies to letrozole / ribociclib: oral tablet.

General adverse events

The most common adverse reactions and laboratory abnormalities (20% or more frequency) were decreased leukocyte count (93%), decreased neutrophil count (93%), neutropenia (75%), decreased hemoglobin count (57%), nausea (52%), decreased lymphocyte count (51%), increased ALT (46%), increased AST (44%), fatigue (37%), diarrhea (35%), alopecia (33%), leukopenia (33%), decreased platelet count (29%), vomiting (29%), constipation (25%), headache (22%), back pain (20%), and increased creatinine (20%).^[Ref]

Hematologic

• Very common (10% or more): Decreased leukocyte count (93%), decreased neutrophil count (93%), neutropenia (75%), decreased hemoglobin count (57%), decreased lymphocyte count (51%), leukopenia (33%), decreased platelet count (29%), anemia (18%), lymphopenia (11%)^[Ref]

Gastrointestinal

• Very common (10% or more): Nausea (52%), diarrhea (35%), vomiting (29%), constipation (25%), stomatitis (12%), abdominal pain (11%)^[Ref]

Hepatic

• Very common (10% or more): Increased ALT (46%), increased AST (44%), abnormal liver function tests (18%)
• Frequency not reported: Increased blood bilirubin^[Ref]

Other

• Very common (10% or more): Fatigue (37%), pyrexia (13%), peripheral edema (12%)
• Uncommon (0.1% to 1%): On-treatment death^[Ref]

Dermatologic

• Very common (10% or more): Alopecia (33%), rash (17%), pruritus (14%)^[Ref]

Nervous system

• Very common (10% or more): Headache (22%)
• Common (1% to 10%): Syncope^[Ref]

Musculoskeletal

• Very common (10% or more): Arthralgia (33%), back pain (20%)
• Common (1% to 10%): Fractures
• Uncommon (0.1% to 1%): Osteoporosis^[Ref]

Renal

• Very common (10% or more): Increased creatinine (20%)^[Ref]

Metabolic

• Very common (10% or more): Decreased appetite (19%), decreased phosphorus (13%), decreased potassium (11%)
• Frequency not reported: Hypokalemia^[Ref]

Psychiatric

• Very common (10% or more): Insomnia (12%)^[Ref]

Respiratory

• Very common (10% or more): Dyspnea (12%)^[Ref]

Genitourinary

• Very common (10% or more): Urinary tract infection (11%)^[Ref]

Cardiovascular

• Common (1% to 10%): QT interval prolongation^[Ref]

See also:

Further information

Letrozole/ribociclib side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer