Abemaciclib belongs to the class of medications called antineoplastics (anticancer medications). More specifically, it belongs to the class of medications called protein kinase inhibitors. This medication works by slowing the growth and spread of cancer cells.

Abemaciclib is used to treat adults with breast cancer. It is used in combination with other medications to treat early breast cancer that is likely to return. It is used alone or in combination with certain other medications to treat advanced or metastatic (cancer that has spread to other parts of the body) breast cancer that is hormone-receptor (HR) positive and human epidermal growth factor 2 (HER2) receptor negative.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The usual dose of abemaciclib when it is used in combination with another drug for breast cancer is 150 mg taken by mouth twice daily.

When used alone, the usual dose of abemaciclib is 200 mg taken by mouth twice daily.

Swallow the tablets whole. Do not crush or chew the tablets. Abemaciclib may be taken with or without food. It should be taken at approximately the same times each day. Do not take a tablet that is chipped or broken.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose or vomit after taking a dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

50 mg
Each modified oval, beige tablet with "Lilly" debossed on one side and "50" on the other side, contains 50 mg of abemaciclib. Nonmedicinal ingredients: croscarmellose sodium, lactose monohydrate, microcrystalline cellulose 101, microcrystalline cellulose 102, silicon dioxide, and sodium stearyl fumarate; film coating: iron oxide red, iron oxide yellow, polyethylene glycol, polyvinyl alcohol, talc, and titanium dioxide.

100 mg
Each modified oval, white-to-practically-white tablet with "Lilly" debossed on one side and "100" on the other side, contains 100 mg of abemaciclib. Nonmedicinal ingredients: croscarmellose sodium, lactose monohydrate, microcrystalline cellulose 101, microcrystalline cellulose 102, silicon dioxide, and sodium stearyl fumarate; film coating: polyethylene glycol, polyvinyl alcohol, talc, and titanium dioxide.

150 mg
Each modified oval, yellow tablet with "Lilly" debossed on one side and "150" on the other side, contains 150 mg of abemaciclib. Nonmedicinal ingredients: croscarmellose sodium, lactose monohydrate, microcrystalline cellulose 101, microcrystalline cellulose 102, silicon dioxide, and sodium stearyl fumarate; film coating: iron oxide yellow, polyethylene glycol, polyvinyl alcohol, talc, and titanium dioxide.

200 mg
Each modified oval, beige tablet with "Lilly" debossed on one side and "200" on the other side, contains 200 mg of abemaciclib. Nonmedicinal ingredients: croscarmellose sodium, lactose monohydrate, microcrystalline cellulose 101, microcrystalline cellulose 102, silicon dioxide, and sodium stearyl fumarate; film coating: iron oxide red, iron oxide yellow, polyethylene glycol, polyvinyl alcohol, talc, and titanium dioxide.

Do not take this medication if you are allergic to abemaciclib or any ingredients of the medication.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• bloating
• changed sense of taste
• decreased appetite
• dizziness
• dry mouth
• eye pain
• fatigue
• feeling faint
• headache
• increased tear production
• itchiness
• mouth sores
• nausea
• skin rash or inflammation
• spinning sensation
• stomach pain
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• blurred vision
• broken bones or fractures
• diarrhea (liquid or loose stools)
• low levels of calcium in the blood (e.g., muscle cramps in the back and legs, dry skin, confusion, memory loss)
• pain, swelling, numbness, tingling, redness and flaking or blistering palms or soles of feet
• signs of anemia (low red blood cells; e.g., dizziness, pale skin, unusual tiredness or weakness, shortness of breath)
• signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• signs of infection (symptoms may include fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)
• signs of kidney problems (e.g., change in the amount or colour of urine, increased urination at night, blood in the urine, swelling in the feet or legs)
• signs of low potassium levels in the blood (e.g., weakness, fatigue, muscle cramps, irregular heartbeat)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• signs of lung problems (e.g., shortness of breath, painful breathing, tiredness, wheezing, fever or cough)
• symptoms of irregular heart beat (e.g., chest pain, dizziness, rapid, pounding heartbeat, shortness of breath)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of a blood clot in the arm or leg (tenderness, pain, swelling, warmth, or redness in the arm or leg) or lungs (difficulty breathing, sharp chest pain that is worst when breathing in, coughing, coughing up blood, sweating, or passing out)
• signs of a heart attack (e.g., chest pain or pressure, pain extending through shoulder and arm, nausea and vomiting, sweating)
• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of stroke (e.g., sudden or severe headache; sudden loss of coordination; vision changes; sudden slurring of speech; or unexplained weakness, numbness, or pain in arm or leg)
• symptoms of sepsis (blood infection; e.g., high fever, fast heart rate, rapid breathing)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Blood clots: This medication may increase the chance of blood clot formation, causing reduction of blood flow to organs or the extremities.

If you have a history of clotting you may be at increased risk of experiencing blood clot-related problems such as heart attack, stroke, or clots in the deep veins of your leg. Discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

If you experience symptoms such as sharp pain and swelling in the leg, difficulty breathing, or sudden chest pain, contact your doctor immediately.

Diarrhea: Diarrhea is a common side effect of abemaciclib. It is most likely to occur in the first few months that you are taking this medication. Severe diarrhea that is not treated may lead to dehydration and severe complications affecting blood pressure, kidneys, and other organs. If you experience watery or runny bowel movements while you are taking this medication, contact your doctor as soon as possible. If your doctor has recommended an antidiarrheal medication (e.g., loperamide), you should start taking it, as well as increase the amount of fluids you are drinking.

Drowsiness/dizziness: Abemaciclib may cause drowsiness or dizziness, affecting your ability to drive or operate machinery. Avoid driving, operating machinery, or performing other potentially hazardous tasks until you have determined how this medication affects you.

Infection: Like other medications to treat cancer, abemaciclib can reduce the number of cells that fight infection in the body (white blood cells). If possible, avoid contact with people with contagious infections. Tell your doctor immediately if you notice signs of an infection, such as fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness. Your doctor will do blood tests regularly to monitor the number of specific types of blood cells in your blood.

Interactions with food: Grapefruit and grapefruit juice affect how abemaciclib is removed from the body, and may cause the medication to build up in the body. This can lead to potentially harmful side effects. Avoid these foods while you are taking this medication.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects.

Abemaciclib can also reduce liver function. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor will order routine blood tests to test your liver function while you are taking this medication.

If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Lung inflammation: Rarely, some people taking this medication have experienced lung inflammation (interstitial lung disease), causing difficulty breathing. This complication can be serious and sometimes fatal. If you experience new or worsening shortness of breath or cough (with or without fever) at any time while you are taking abemaciclib, contact your doctor immediately.

Pregnancy: This medication should not be used during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately. Women who may become pregnant should use effective birth control while taking abemaciclib and for at least 3 weeks after taking the last dose.

Breast-feeding: It is not known if abemaciclib passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Women taking abemaciclib should avoid breast-feeding while taking this medication and for at least 3 weeks after taking the last dose.

Children: The safety and effectiveness of using this medication have not been established for children.

Seniors: People over the age of 65 may be more likely to experience side effects from taking abemaciclib.

There may be an interaction between abemaciclib and any of the following:

• apalutamide
• aprepitant
• "azole" antifungals (e.g., itraconazole, ketoconazole, voriconazole)
• BCG
• baricitinib
• bosentan
• calcium channel blockers (e.g., amlodipine, diltiazem, verapamil)
• cladribine
• clozapine
• cobicistat
• conivaptan
• cyclosporine
• danazol
• deferiprone
• denosumab
• digoxin
• dronedarone
• echinacea
• elagolix
• enzalutamide
• everolimus
• glecaprevir and pibrentasvir
• grapefruit juice
• grazoprevir
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delavirdine, efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
• leflunomide
• lumacaftor and ivacaftor
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• mesalamine
• metformin
• mifepristone
• mitotane
• modafinil
• natalizumab
• ocrelizumab
• olsalazine
• pimecrolimus
• protein kinase inhibitors (e.g., ceritinib, crizotinib, dabrafenib, idelalasib, imatinib, nilotinib, palbociclib)
• rifabutin
• rifampin
• St. John's wort
• seizure medications (e.g., carbamazepine, phenobarbital, phenytoin, primidone)
• sphingosine 1-phosphate receptor inhibitors (e.g., fingolimod, ozanimod)
• tacrolimus
• tofacitinib
• upadacitinib
• vaccines

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.