Cobimetinib belongs to the group of medications used to fight cancer, called antineoplastics. Specifically, it belongs to the group of medications called protein kinase inhibitors. Cobimetinib works by recognizing and attaching to certain types of cancer cells. This may slow down or stop cancers from growing and dividing.

This medication is used along with vemurafenib to treat melanoma, a type of skin cancer. This combination of medications is to treat melanoma that has a mutation (a change) in the "BRAF" gene and that cannot be removed by surgery or has spread to other parts of the body. Before using cobimetinib and vemurafenib, it is important to have the cancer tested for this change in the "BRAF" gene.

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 recommended adult dose of cobimetinib is 60 mg (three 20 mg tablets) taken once daily. Cobimetinib is taken daily for 21 days, and then stopped for 7 days. This forms a 28-day cycle. After 7 days without taking cobimetinib, the 28-day cycle begins again.

This medication may be taken with or without food. The tablets should be swallowed whole, with a glass of water.

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 vomit after taking a dose, do not take another dose. Continue with your regular dosing schedule the next day.

If you miss a dose, and it is less than 12 hours since the missed dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next 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.

Each white, round, film-coated tablet with "COB" debossed on one side contains 20 mg of cobimetinib (as 22.2 mg of cobimetinib fumarate). Nonmedicinal ingredients: croscarmellose sodium, lactose monohydrate, magnesium stearate, and microcrystalline cellulose. The film-coating mixture includes (alphabetical order) polyethylene glycol 3350 (macrogol 3350), polyvinyl alcohol, talc, and titanium dioxide.

Do not take this medication if you are allergic to cobimetinib 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.

• abdominal pain
• chills
• diarrhea
• dizziness
• dry mouth
• fever
• mouth sores, including cold sores
• muscle aches
• nausea
• red, swollen, or itchy eyes
• symptoms of the common cold (e.g., sore throat, stuffy, or runny nose)
• 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:

• acne-like skin rash
• hives
• increased blood pressure
• increased sensitivity to sunlight (e.g., sunburn, rash)
• new skin cancer (e.g., new skin sore, wart, or bump on the skin that bleeds or does not heal)
• 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 dehydration (e.g., decreased urine, dry skin, dry and sticky mouth, sleepiness, dizziness, headache, thirst, confusion)
• 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 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 muscle damage (e.g., unexplained muscle pain, tenderness, or weakness, or brown or discoloured urine)
• swelling ankles or feet
• swelling, pain, and redness of the palms of the hands and soles of the feet
• symptoms of heart problems (e.g., persistent cough, wheezing, shortness of breath, tiredness)
• symptoms of high blood sugar (e.g., frequent urination, increased thirst, excessive eating, unexplained weight loss, poor wound healing, infections, fruity breath odour)
• symptoms of irregular heartbeat (e.g., fast heartbeat, weakness, tiredness, dizziness, lightheadedness, confusion, chest pain, trouble breathing)
• symptoms of lung inflammation (e.g., trouble breathing, cough, fever or chills)
• tender red bumps under the skin
• vision problems (e.g., blurred vision, halos, missing parts of vision)

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

• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort
• signs of bleeding in the stomach (e.g., bloody, black, or tarry stools; spitting up of blood; vomiting blood or material that looks like coffee grounds)

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.

Anemia: Cobimetinib may cause low levels of red blood cells. If you experience symptoms of reduced red blood cell count (anemia) such as shortness of breath, feeling unusually tired, or pale skin, contact your doctor as soon as possible.

Your doctor will do blood tests regularly to monitor the number of specific types of blood cells, including red blood cells, in your blood.

Bleeding: Cobimetinib can increase the risk of experiencing uncontrolled bleeding. If you have risk factors for bleeding, such as medical conditions that reduce clotting or you are taking blood thinners, 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.

Driving/operating machinery: Cobimetinib may cause drowsiness, dizziness, or vision changes 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.

Heart problems: This medication may worsen symptoms of heart disease. If you have heart disease such as angina, congestive heart failure, or arrhythmia, 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. Contact your doctor as soon as possible if you develop symptoms of heart problems such as shortness of breath, chest pain, rapid heartbeat, or swollen ankles. Your doctor may want to monitor your heart function periodically while you are using this medication, to ensure that any problems are identified early.

High blood pressure: Cobimetinib may increase your blood pressure. Your doctor will monitor your blood pressure while you are taking this medication. If you have high blood pressure, 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.

Liver function: Decreased liver function may cause cobimetinib to build up in the body, causing side effects. It has also been reported to cause decreased liver function. 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.

Your doctor may want to test your liver function regularly with blood tests while you are taking this medication. This often allows reduced liver function to be identified before it becomes too severe.

Muscle effects: Muscle damage has been associated with the use of cobimetinib. Report any unexplained muscle pain, tenderness, weakness, or cramps, or any brown or discoloured urine to your doctor immediately, particularly if you are also experiencing malaise (a general feeling of being unwell) or fever.

Sensitivity to sunlight: This medication may increase the sensitivity of the skin to sunlight, increasing the risk of sunburn. Avoid exposure to sunlight as much as possible, particularly between the hours of 10 am and 2 pm, while you are taking this medication and for 7 days after completing treatment. Wear a broad-spectrum sunscreen and lip balm with an SPF of 50 or greater. If you notice any unusual skin rash or peeling, contact your doctor immediately.

Vision: This medication may cause fluid to build up in the back of the eye. It may also contribute to a blockage of the blood vessels that lead out of the eye. If you notice any vision changes or problems, contact your doctor as soon as possible.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. Cobimetinib may cause harm to a developing baby if taken by the mother. If you become pregnant while taking this medication, contact your doctor immediately. Use 2 forms of effective birth control while taking this medication and for at least 3 months after stopping treatment.

Breast-feeding: It is not known if cobimetinib passes into breast milk. If you are breast-feeding and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

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

Seniors: Seniors may be at an increased risk of experiencing side effects of this medication. It may be necessary to use a lower dose of this medication to reduce the severity of side effects.

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

• amiodarone
• apalutamide
• aprepitant
• "azole" antifungals (e.g., itraconazole, ketoconazole, voriconazole)
• bosentan
• cobicistat
• conivaptan
• desmopressin
• diltiazem
• dronedarone
• enzalutamide
• grapefruit juice
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
• lumacaftor and ivacaftor
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• methoxsalen
• mifepristone
• mitotane
• modafinil
• porfimer
• other protein kinase inhibitors (e.g., ceritinib, crizotinib, dabrafenib, idelalisib, imatinib)
• rifabutin
• rifampin
• St. John's wort
• seizure medications (e.g., carbamazepine, clobazam, lamotrigine, levetiracetam, lomitapide, phenobarbital, phenytoin)
• stiripentol
• tocilizumab
• verapamil
• verteporfin

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.