Cobimetinib is used along with vemurafenib (Zelboraf) to treat certain types of melanoma (a type of skin cancer) that cannot be treated with surgery or that has spread to other parts of the body. Cobimetinib is also used to treat histiocytic neoplasms (conditions that cause an overproduction and accumulation of a type of white blood cell in parts of the body). Cobimetinib is in a class of medications called kinase inhibitors. It works by blocking the action of an abnormal protein that signals cancer cells to multiply. This helps slow or stop the spread of cancer cells.

🔔 How should this medicine be used?

Cobimetinib comes as a tablet to take by mouth with or without food. It is usually taken once daily for the first 21 days of a 28-day cycle. Take cobimetinib at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take cobimetinib exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

If you vomit after taking cobimetinib do not take another dose. Continue your regular dosing schedule.

Your doctor may decrease your dose of cobimetinib or permanently or temporarily stop your treatment. This depends on how well the medication works for you and the side effects you experience. Be sure to tell your doctor how you are feeling during your treatment with cobimetinib.

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.

🔔 Other uses for this medicine

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

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🔔 What special precautions should I follow?

Before taking cobimetinib,

  • tell your doctor and pharmacist if you are allergic to cobimetinib, any other medications, or any of the ingredients in cobimetinib tablets. Ask your pharmacist for a list of the ingredients.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, and nutritional supplements you are taking or plan to take. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • tell your doctor what herbal products you are taking, especially St. John’s Wort. Do not take St. John’s Wort while you are taking cobimetinib.
  • tell your doctor if you have or have ever had have skin conditions other than melanoma; bleeding problems; vision problems; any condition that affects your muscles; or heart or liver disease.
  • you should know that cobimetinib may decrease fertility in men and women. However, you should not assume that you or your partner cannot become pregnant. Tell your doctor if you are pregnant or plan to become pregnant. Use a reliable method of birth control to prevent pregnancy during your treatment and for 2 weeks after you stop taking cobimetinib. Talk to your doctor about birth control methods that will work for you. If you become pregnant while taking cobimetinib, call your doctor immediately. Cobimetinib may harm the fetus.
  • tell your doctor if you are breastfeeding. You should not breastfeed while taking cobimetinib and for 2 weeks after your last dose.
  • plan to avoid unnecessary or prolonged exposure to sunlight and to wear protective clothing, sunglasses, lip balm and sunscreen (SPF 30 or higher). Cobimetinib may make your skin sensitive to sunlight. Tell your doctor right away if you get a sunburn.
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🔔 What special dietary instructions should I follow?

Do not eat grapefruit or drink grapefruit juice while taking this medication.

🔔 What should I do if I forget a dose?

Skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

🔔 What side effects can this medication cause?

Cobimetinib may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • mouth ulcers
  • hair loss
  • diarrhea
  • nausea
  • vomiting
  • heartburn or indigestion
  • dry mouth
  • mouth pain
  • fever, chills, sore throat, frequent or painful urination, or other signs of infection
  • falling

Some side effects can be serious. If you experience any of these symptoms or those in the SPECIAL PRECAUTIONS section, call your doctor immediately or get emergency medical treatment:

  • rash that covers a large area of your body, blisters, or peeling skin
  • changes in skin appearance
  • new wart
  • skin sore or red bump that bleeds or does not heal
  • change in size or color of a mole
  • unusual bleeding or bruising tarry or black stools, blood in urine, unusual vaginal bleeding, stomach pain, headache or dizziness
  • coughing or wheezing; rapid, irregular, or pounding heartbeat; shortness of breath; tiredness; or swelling of the face, arms, legs, ankles, or feet
  • muscle spasms, pain, or weakness
  • changes in vision, including seeing halos (blurred outline around objects), blurred vision, or loss of vision
  • yellowing of the skin or eyes, dark-colored (tea-colored) urine, pain in upper right part of the stomach, nausea, vomiting, or loss of appetite

Cobimetinib may increase the risk that you will develop new skin cancers. Talk to your doctor about the risks of taking this medication.

Cobimetinib may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online ( or by phone (1-800-332-1088).

🔔 What should I know about storage and disposal of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website ( for more information if you do not have access to a take-back program.

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It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach.

🔔 In case of emergency/overdose

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

🔔 What other information should I know?

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body’s response during and after therapy. Your doctor will check your skin for any changes before, every 2 months during your treatment, and for up to 6 months after treatment.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.