Tucatinib
Tucatinib is a targeted cancer pill that blocks the HER2 protein, used with other medicines for HER2-positive breast cancer and HER2-positive colorectal cancer.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 1 clinical label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
Tucatinib (Tukysa) is a targeted cancer medicine that blocks HER2, a growth protein on some cancer cells, used with other drugs for advanced HER2-positive breast cancer (including spread to the brain) and HER2-positive colorectal cancer, a specialist option after earlier treatments, on the U.S. market since about 2020. It is usually manageable, but diarrhea is the side effect most people notice, often with nausea and mouth sores. Severe or nonstop diarrhea is the thing to act on, since it can dehydrate you quickly, so call your care team early. Liver injury is the other main risk, so liver blood tests are checked before starting and about every three weeks.
Clinical pearls
- Take doses about 12 hours apart, with or without food, and swallow tablets whole, never using a cracked or broken one.
- If you vomit right after a dose, do not take another; just take the next one at the usual time.
- Avoid gemfibrozil, a cholesterol drug, and rifampin, an antibiotic, because they push tucatinib levels too high or too low.
- Tucatinib raises levels of digoxin and of midazolam, a sedative used for procedures, so tell every prescriber you take it.
Patient information guide A plain-language walkthrough of Tucatinib, written from its FDA label.
What Tucatinib is used for
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Tucatinib is used in adults with HER2-positive cancers:
- Tukysa, with trastuzumab and capecitabine, for advanced unresectable or metastatic HER2-positive breast cancer, including cancer that has spread to the brain, after one or more prior anti-HER2 treatments.
- Tukysa, with trastuzumab, for RAS wild-type HER2-positive unresectable or metastatic colorectal cancer that progressed after fluoropyrimidine-, oxaliplatin- and irinotecan-based chemotherapy.
The colorectal use has accelerated approval based on tumor response, so continued approval may depend on confirmatory trials.
How Tucatinib works
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Tucatinib blocks HER2, a protein on some tumor cells that signals them to grow. By blocking it, tucatinib shuts down growth signals inside the cell, including the MAPK and AKT pathways.
In lab and animal studies, it slowed HER2-positive tumor growth. Combined with trastuzumab, the effect was stronger than either drug alone.
Tucatinib dosage
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Tukysa tablets are taken by mouth twice daily, about 12 hours apart and at the same times each day.
- Take with or without food.
- Swallow whole. Do not chew, crush or split, and do not use a broken or cracked tablet.
- If you vomit or miss a dose, take the next dose at the usual time.
- Treatment continues until the cancer progresses or side effects become unacceptable.
Your doctor may lower the dose for side effects, severe liver impairment or certain interacting drugs.
Dosing details from the FDA-approved label
From the Tucatinib prescribing information (“Dosage and Administration”). Doses are set by your prescriber for your product, condition, kidney function and age — never change a dose on your own.
- Metastatic Breast Cancer
- 300 mg taken orally twice daily in combination with trastuzumab and capecitabine until disease progression or unacceptable toxicity
- Take approximately 12 hours apart and at the same time each day with or without a meal
- Capecitabine 1000 mg/m2 orally twice daily taken within 30 minutes after a meal; TUKYSA and capecitabine can be taken at the same time
- Unresectable or Metastatic Colorectal Cancer
- 300 mg taken orally twice daily in combination with trastuzumab until disease progression or unacceptable toxicity
- Take approximately 12 hours apart and at the same time each day with or without a meal
- Confirm HER2 protein overexpression and RAS wild-type in tumor specimens prior to initiation
- Severe hepatic impairment (Child-Pugh C)
- 200 mg orally twice daily
- Reduced from the recommended dosage
- Concomitant use with a strong CYP2C8 inhibitor that cannot be avoided
- 100 mg orally twice daily
- After discontinuation of the inhibitor for 3 elimination half-lives, resume the TUKYSA dose taken prior to the inhibitor
- Dose reductions for adverse reactions
- First: 250 mg orally twice daily
- Second: 200 mg orally twice daily
- Third: 150 mg orally twice daily
- Permanently discontinue in patients unable to tolerate 150 mg orally twice daily
Read the label’s full dosing text
2 DOSAGE AND ADMINISTRATION • In patients with unresectable or metastatic colorectal cancer, confirm the presence of HER2 protein overexpression and RAS wild-type in tumor specimens prior to the initiation of TUKYSA ( 2.1 ) • Recommended dosage: 300 mg taken orally twice daily with or without food. ( 2.1 ) • For patients with severe hepatic impairment, the recommended dosage is 200 mg orally twice daily. ( 2.3 , 8.7 ) 2.1 Patient Selection Select patients for treatment of unresectable or metastatic colorectal cancer with TUKYSA based on the presence of: • HER2 overexpression or gene amplification [see Clinical Studies (14.2) ]. FDA-approved tests for the detection of HER2 overexpression and gene amplification in patients with unresectable or metastatic colorectal cancer are not currently available, and • RAS wild-type [see Clinical Studies (14.2) ]. Information on FDA-approved tests for the detection of RAS mutations in patients with unresectable or metastatic colorectal cancer is available at http://www.fda.gov/CompanionDiagnostics . 2.2 Recommended Dosage Metastatic Breast Cancer The recommended dosage of TUKYSA is 300 mg taken orally twice daily in combination with trastuzumab and capecitabine until disease progression or unacceptable toxicity [see Clinical Studies (14.1) ] . Unresectable or Metastatic Colorectal Cancer The recommended dosage of TUKYSA is 300 mg taken orally twice daily in combination with trastuzumab until disease progression or unacceptable toxicity [see Clinical Studies (14.2) ]. Advise patients to swallow TUKYSA tablets whole and not to chew, crush, or split prior to swallowing. Advise patients not to ingest tablet if it is broken, cracked, or not otherwise intact. Advise patients to take TUKYSA approximately 12 hours apart and at the same time each day with or without a meal. If the patient vomits or misses a dose of TUKYSA, instruct the patient to take the next dose at its usual scheduled time. When given in combination with TUKYSA, the recommended dosage of capecitabine is 1000 mg/m 2 orally twice daily taken within 30 minutes after a meal. TUKYSA and capecitabine can be taken at the same time. Refer to the Full Prescribing Information for trastuzumab and capecitabine for additional information.
Excerpted — the section continues on the label. Read the full Dosage and Administration section on DailyMed →
Tucatinib side effects
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The most common side effects include:
Common side effects
- Diarrhea
- Nausea and vomiting
- Hand-foot skin reaction (redness, soreness on palms and soles)
- Mouth sores
- Rash
- Decreased appetite
- Tiredness
- Abdominal pain
- Anemia (low red blood cells)
- Tiredness, abdominal pain and fever (mainly in colorectal cancer use)
When to get medical help
- Call your doctor right away if you have severe or persistent diarrhea, or signs of dehydration such as dizziness or very little urine.
- Tell your doctor about signs of liver problems, since liver injury can be severe and needs blood test monitoring.
- Get help if you notice a pregnancy or suspect one during treatment, since the drug can harm a fetus.
- Report any side effect that is severe or not going away, as your doctor may pause or lower the dose.
Contact your doctor promptly about severe diarrhea or signs of liver problems. Blood tests may also show raised creatinine, which can happen without harming kidney filtering.
Tucatinib warnings and precautions
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- Severe diarrhea: can cause dehydration, low blood pressure, kidney injury and death.
- Liver injury: liver tests are checked before treatment and every 3 weeks.
- Fetal harm: can harm an unborn baby; contraception is needed.
- Your doctor may hold, reduce or stop the drug depending on severity.
Tucatinib interactions
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Some medicines change tucatinib levels, or tucatinib changes theirs.
- Strong CYP2C8 inhibitors (e.g., gemfibrozil): raise tucatinib levels; avoid or lower the dose.
- Strong CYP3A inducers or moderate CYP2C8 inducers (e.g., rifampin): lower tucatinib levels and may reduce its effect.
- CYP3A substrates (e.g., midazolam): tucatinib raises their levels; avoid if risk is serious.
- P-gp substrates (e.g., digoxin): levels rise; dose may need reducing.
- Metformin: levels rose modestly in a study.
Interactions listed in the FDA-approved label
From the Tucatinib prescribing information (“Drug Interactions”): what the manufacturer studied or reported to the FDA.
- Strong CYP3A inducers or moderate CYP2C8 inducers: Decreased tucatinib plasma concentrations, which may reduce TUKYSA activity. Avoid concomitant use.
- Strong CYP2C8 inhibitors: Increased tucatinib plasma concentrations, which may increase the risk of TUKYSA toxicity. Avoid concomitant use; reduce TUKYSA dose to 100 mg orally twice daily if concomitant use cannot be avoided.
- Moderate CYP2C8 inhibitors: May increase tucatinib plasma concentrations and the risk of TUKYSA toxicity. Increase monitoring for TUKYSA toxicity.
- CYP3A substrates: TUKYSA increased the plasma concentrations of the CYP3A substrate, which may increase its toxicity. Avoid concomitant use where minimal concentration changes may lead to serious or life-threatening toxicities; if unavoidable, decrease the CYP3A substrate dosage in accordance with approved product labeling.
- P-glycoprotein (P-gp) substrates: TUKYSA increased the plasma concentrations of the P-gp substrate, which may increase its toxicity. Consider reducing the dosage of P-gp substrates where minimal concentration changes may lead to serious or life-threatening toxicities.
Read the label’s full interactions text
7 DRUG INTERACTIONS • Strong CYP3A Inducers or Moderate CYP2C8 Inducers : Avoid concomitant use. ( 7.1 ) • Strong CYP2C8 Inhibitors : Avoid concomitant use; reduce TUKYSA dose if concomitant use cannot be avoided. ( 2.4 , 7.1 ) • CYP3A Substrates : Avoid concomitant use with CYP3A substrates, where minimal concentration changes may lead to serious or life-threatening toxicities. ( 7.2 ) • P-gp Substrates : Consider reducing the dose of P-gp substrates, where minimal concentration changes may lead to serious or life-threatening toxicities. ( 7.2 ) 7.1 Effects of Other Drugs on TUKYSA Table 7 summarizes the effect of other drugs on TUKYSA. Table 7: Drug Interactions that Affect TUKYSA Strong CYP3A Inducers or Moderate CYP2C8 Inducers Clinical Impact Concomitant use of TUKYSA with a strong CYP3A or moderate CYP2C8 inducer decreased tucatinib plasma concentrations [see Clinical Pharmacology (12.3) ] , which may reduce TUKYSA activity. Management Avoid concomitant use of TUKYSA with a strong CYP3A inducer or a moderate CYP2C8 inducer. Strong or Moderate CYP2C8 Inhibitors Clinical Impact Concomitant use of TUKYSA with a strong CYP2C8 inhibitor increased tucatinib plasma concentrations [see Clinical Pharmacology (12.3) ] , which may increase the risk of TUKYSA toxicity. Management Avoid concomitant use of TUKYSA with a strong CYP2C8 inhibitor. Increase monitoring for TUKYSA toxicity with moderate CYP2C8 inhibitors. 7.2 Effects of TUKYSA on Other Drugs Table 8 summarizes the effect of TUKYSA on other drugs. Table 8: TUKYSA Drug Interactions that Affect Other Drugs CYP3A Substrates Clinical Impact Concomitant use of TUKYSA with a CYP3A substrate increased the plasma concentrations of CYP3A substrate [see Clinical Pharmacology (12.3) ] , which may increase the toxicity associated with a CYP3A substrate. Management Avoid concomitant use of TUKYSA with CYP3A substrates, where minimal concentration changes may lead to serious or life-threatening toxicities.
Excerpted — the section continues on the label. Read the full Drug Interactions section on DailyMed →
Not a complete list. The label covers the interactions the manufacturer studied or reported, and our own interaction database does not cover every medicine either. Bring your full medication list, including vitamins and herbal products, to your pharmacist.
Before taking Tucatinib
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- No contraindications are listed.
- Pregnancy: can cause fetal harm; a pregnancy test is done first.
- Use effective contraception during treatment and for 1 week after (females and males with female partners).
- Do not breastfeed during treatment and for 1 week after.
- Severe liver impairment requires a lower dose.
- Children: safety and effectiveness not established.
- Older adults: serious side effects were reported more often in patients 65 and older in the breast cancer trial.
What Tucatinib does in the body
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Tucatinib blocks HER2 and HER3 signaling in HER2-expressing tumor cells. At the recommended dose, no large increase in QTc (a heart rhythm measure) was seen. The relationship between drug exposure and effect has not been fully worked out.
How your body processes Tucatinib
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Tucatinib reaches peak blood levels in about 2 hours. A high-fat meal did not change its effect in a meaningful way. It is broken down mainly by the liver enzyme CYP2C8 and partly by CYP3A.
Steady levels build in about 4 days, and the half-life is roughly 12 to 16 hours. Most of it leaves in the stool. Severe liver impairment raises levels, while mild to moderate kidney or liver impairment did not matter much.
How to store Tucatinib
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Store at controlled room temperature, 20ºC to 25ºC (68ºF to 77ºF); excursions permitted from 15ºC to 30ºC (59ºF to 86ºF) . Store in original container to protect from moisture.
Written from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
Supplements & herbs that interact with Tucatinib
178 supplements and herbal products have documented interactions with Tucatinib in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 6
- Moderate · 137
- Minor · 35
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
Tucatinib: pharmacist answers to common questions
Quick, plain-English answers to the questions patients ask most about Tucatinib — the kind of thing our pharmacy team would talk through with you at the counter.
What is Tukysa for?
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How do I take it?
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What side effects should I expect?
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Why do I need blood tests?
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Do I need to worry about other medicines I take?
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Is it safe during pregnancy?
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Is Tucatinib available over the counter?
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When was Tucatinib first available?
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Answers drafted from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
More about Tucatinib on HelloPharmacist
Tucatinib forms and strengths (how it comes)
Tucatinib is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Need a version that does not list lactose, a gluten source, a dye or gelatin? Inactive ingredients differ by manufacturer: see Tucatinib inactive ingredients by manufacturer.
Tablet
How this form is used
- Tukysa is used with trastuzumab and capecitabine for HER2-positive breast cancer.
- Tukysa is used with trastuzumab for RAS wild-type HER2-positive colorectal cancer.
- Tukysa tablets are swallowed whole, not chewed, crushed or split.
- Tukysa is taken about 12 hours apart, with or without food.
- If you vomit or miss a dose of Tukysa, take the next dose at the usual time.
Tucatinib on the U.S. market: products, makers and brands
How Tucatinib appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
1 company lists 2 Tucatinib product records with the FDA, mostly as tablet; the earliest marketing or approval year on record is 2020. Brand names on the directory include Tukysa; the rest are generics.
Also listed with the FDA, not a patient dose form: Powder (5) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
How widely Tucatinib is used (Medicaid data)
A general measure of how commonly Tucatinib is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Tucatinib is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Tucatinib prescribed? Of the 1,601 medications we measure, Tucatinib ranks #1,316 by Medicaid prescriptions — more than 18% of them.
Utilization by Tucatinib product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
tucatinib 150 MG Oral Tablet Most dispensed
Summed across the 2 of 4 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 2361290
tucatinib 50 MG Oral Tablet
Summed across the 1 of 2 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 2361298
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Tucatinib, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 3 of 6 listed Tucatinib NDCs with Medicaid activity.
Compare Tucatinib products
A representative set of FDA-listed product records for Tucatinib — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Tablet | ||||
| 50 mg | Oral | Seagen Inc. | NDA | View NDC → |
| 150 mg | Oral | Seagen Inc. | NDA | View NDC → |
Showing 2 of 2 products — FDA National Drug Code Directory. See every product, package size and price: browse all 2 Tucatinib NDCs →
Tucatinib side effects reported to the FDA (FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Tucatinib — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Tucatinib in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
Tucatinib FDA approval history
How Tucatinib went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
Tucatinib recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
The FDA’s enforcement reports list no Tucatinib recalls since July 2021.
✅No Tucatinib recalls on record since July 2021Source: FDA enforcement (recall) reports, via openFDA; our copy was last updated Sep 24, 2026.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 2361285 1 dose form · 2 strengths
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Dose form (SCDF) Oral Tablet RxCUI 2361289In current FDA listings
Look up RxCUI 2361285 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
Tucatinib supply and shortage status
Whether Tucatinib is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
Tucatinib brand names
Tucatinib is sold under one brand name in the FDA directory — Tukysa. A brand and its generic contain the same active ingredient; the brand name belongs to one company's product.
Who makes Tucatinib: manufacturers and labelers
One company lists Tucatinib products with the FDA. By number of product records, the largest are Seagen Inc.. Labelers include manufacturers and repackagers; the product in your bottle depends on which one your pharmacy stocks.
Tucatinib drug class (RxNorm)
Tucatinib belongs to the Kinase Inhibitor class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
Sources for this Tucatinib page
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How this page is built
HelloPharmacist combines public FDA and NLM records and does not author the underlying clinical facts. The plain-language sections are written with AI from the FDA-approved label text and reviewed by our pharmacy team before publication. Seagen Inc. is the representative DailyMed label linked for verification and dates. This is general education, not medical advice: always talk to your doctor or pharmacist about your own medicines. How we build and review drug pages →