Approved indications: Cometriq is an oral kinase inhibitor approved in the United States for the treatment of patients with progressive, metastatic medullary thyroid cancer (MTC); its safety and effectiveness in children have not been established.

Off-label uses: Other cabozantinib products (tablet formulations) are approved for certain kidney, liver, and differentiated thyroid cancers, but the Cometriq capsule form itself is seldom used off-label, and any such use is typically limited to specialist care or clinical trials.

Efficacy expectations: In a large study of metastatic MTC, Cometriq significantly delayed cancer growth compared with placebo and produced tumor shrinkage or disease stabilization in most patients; responses are usually first seen on imaging within about 2–3 months, benefits can last many months or longer in responders, and overall its ability to control disease is comparable to other targeted drugs for MTC even though there are no direct head-to-head comparison trials.

Typical dosing and populations: For adults with progressive, metastatic medullary thyroid cancer, the usual starting dose is 140 mg of Cometriq taken by mouth once daily; dose reductions (for example to 100 mg and then to 60 mg once daily) are commonly used to manage side effects, and patients with mild to moderate liver impairment are started at a lower dose (with use generally avoided in severe hepatic impairment); safety and dosing have not been established in children.

How to take the medicine: Swallow the capsules whole with a full glass of water, without opening, crushing, or chewing them; take Cometriq on an empty stomach, not eating for at least 2 hours before and at least 1 hour after each dose, take it at the same time every day, do not substitute Cometriq capsules with cabozantinib tablets, and avoid grapefruit products and St. John’s wort while on therapy.

Special dosing instructions: Because Cometriq can impair wound healing and increase bleeding risk, it is usually stopped at least 3 weeks before planned surgery or invasive dental procedures and restarted no sooner than about 2 weeks after major surgery, once wounds have adequately healed, and the dose may be temporarily held or reduced based on blood pressure readings, lab test results, and the severity of side effects.

Missed dose and overdose guidance: If a dose is missed and the next scheduled dose is due in less than 12 hours, skip the missed dose and take only the next dose at the regular time (do not double up to make up for a missed dose); if more Cometriq than prescribed is taken, contact a healthcare provider immediately, call Poison Control at 1-800-222-1222 in the U.S., or seek emergency medical care.

Common side effects: Very common reactions (often in about one-third to more than half of patients) include diarrhea, mouth sores, hand–foot skin reactions on the palms and soles, decreased appetite and weight loss, nausea, vomiting, constipation, fatigue or weakness, abdominal pain, changes in taste, hair color changes, and high blood pressure; these usually begin in the first few weeks of therapy and can range from mild to severe, frequently requiring temporary treatment breaks or dose reductions.

Serious or rare adverse effects needing urgent medical attention:

• Tears in the stomach or intestinal wall (gastrointestinal perforation) or abnormal connections between organs (fistulas), often presenting as severe or persistent abdominal pain, fever, or signs of infection.
• Severe bleeding, such as coughing or vomiting blood, black or bloody stools, unusually heavy menstrual bleeding, or any other unexpected major bleeding.
• Blood clots, heart attack, stroke, or heart failure, signaled by sudden chest pain, shortness of breath, swelling, one-sided weakness, trouble speaking or seeing, or sudden severe headache.
• Wound-healing problems after surgery or dental procedures, including wounds that open, leak, or do not heal.
• Severe jaw bone problems (osteonecrosis of the jaw), with jaw pain, toothache, loose teeth, or sores that do not heal in the mouth.
• Kidney problems with protein in the urine, causing swelling of the hands, arms, legs, or feet or sudden weight gain.
• Low blood calcium (hypocalcemia) causing muscle cramps or spasms, tingling around the mouth or in fingers and toes, seizures, or confusion.
• A brain circulation problem called reversible posterior leukoencephalopathy syndrome (RPLS), with headaches, seizures, confusion, or vision changes.
• Liver injury, which may show as yellowing of the skin or eyes, dark urine, right upper abdominal pain, or unusual fatigue.

Warnings and precautions: Cometriq can harm an unborn baby, so pregnancy must be avoided during treatment and for 4 months after the last dose; breastfeeding is not recommended during treatment and for 4 months afterward; it is not known if it is safe or effective in children; dose reduction is required in mild to moderate liver impairment and the drug is generally not recommended in severe hepatic impairment; caution is needed in people with significant kidney disease, uncontrolled high blood pressure, a recent history of serious bleeding or coughing up blood, or those who are planning major surgery or invasive dental work.

Safety compared with similar drugs and safety information sources: Like other multi-kinase inhibitors used for thyroid cancer, Cometriq has a substantial side-effect burden and high rates of dose interruption or reduction, but the types of side effects are broadly similar to others in its class and are usually manageable with close monitoring and supportive care; side effects can be reported directly to the U.S. Food and Drug Administration (FDA) through the MedWatch program (online or by calling 1-800-FDA-1088), and the latest safety communications are available in the current FDA prescribing information and on the manufacturer’s website.

Key drug, food, and supplement interactions:

• Strong CYP3A4 inhibitors (such as certain antifungals, macrolide antibiotics, and some HIV or hepatitis C medicines) can raise cabozantinib levels and increase side effects, so an alternative drug or Cometriq dose adjustment may be needed.
• Strong CYP3A4 inducers (for example rifampin, carbamazepine, phenytoin, some other seizure medicines, and the herbal product St. John’s wort) can lower cabozantinib levels and reduce effectiveness, and are generally avoided or used only with careful specialist guidance.
• Grapefruit and grapefruit juice can act like CYP3A4 inhibitors and should be avoided while taking Cometriq.
• Medicines that increase bleeding risk (such as anticoagulants, antiplatelet drugs, and nonsteroidal anti-inflammatory drugs) or that raise blood pressure may add to Cometriq’s risks and require closer monitoring and dose adjustments.
• Always review over-the-counter medicines, vitamins, and herbal supplements with the prescriber, since several may interact or worsen side effects.

Precautions and conditions where use may be unsafe: Extra caution or alternative therapy may be needed in people with uncontrolled high blood pressure, recent serious bleeding or coughing up blood, significant liver or kidney disease, low blood calcium, protein in the urine, major dental problems, or a history of blood clots, heart attack, stroke, or other serious arterial disease.

Monitoring needs: During treatment, clinicians typically monitor blood pressure regularly and perform periodic blood tests (blood counts, liver and kidney function, thyroid function, calcium and other electrolytes), urine tests for protein, oral and dental exams, heart evaluations when indicated, and imaging scans to assess tumor response and detect complications early.

Q: What is Cometriq used for?
A: Cometriq is a prescription medicine used to treat medullary thyroid cancer that has spread to other parts of the body and is getting worse.

Q: How long will I need to take Cometriq?
A: Most people continue taking Cometriq once daily until the cancer clearly worsens on scans or side effects become too severe to manage, with doses often adjusted over time.

Q: Can I take Cometriq with food or other medicines?
A: You should not eat for at least 2 hours before and at least 1 hour after each dose, and you should review all prescription drugs, over-the-counter medicines, and supplements with your healthcare provider because many can interact with Cometriq.

Q: What should I avoid while taking Cometriq?
A: Avoid grapefruit or grapefruit juice, St. John’s wort, starting new medicines without checking for interactions, and having planned surgery or major dental work without first discussing timing and temporary drug stoppage with your care team.

Q: How soon might I know if Cometriq is working?
A: Most people are evaluated with imaging every few months, and signs that Cometriq is working include tumors shrinking or remaining stable on scans and, in some cases, gradual improvement or stabilization of symptoms.

Q: Is Cometriq safe during pregnancy or breastfeeding?
A: Cometriq can harm an unborn baby, so effective birth control is needed during treatment and for 4 months after the last dose, and breastfeeding is not recommended during this period.

Storage: Store Cometriq capsules at room temperature (68°F to 77°F / 20°C to 25°C), in the original packaging, protected from moisture, heat, and light, and keep them out of reach of children and pets.

Disposal: When treatment is stopped, use a pharmacy or community drug take-back program if available; if none is available, keep capsules in their original form, mix them (inside a sealed container or bag) with an undesirable substance such as used coffee grounds or cat litter, then place in household trash according to local rules, and do not flush medicines down the toilet unless specifically instructed.