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Lapatinib Dosage

Applies to the following strengths: 250 mg

The information at Drugs.com is not a substitute for medical advice. Always consult your doctor or pharmacist.

Usual Adult Dose for Breast Cancer

-HER2-POSITIVE METASTATIC BREAST CANCER (in combination with capecitabine): 1250 mg orally once a day on Days 1 to 21 continuously in repeating 21-day cycles until disease progression or unacceptable toxicity.

-HORMONE RECEPTOR-POSITIVE, HER2-POSITIVE METASTATIC BREAST CANCER (in combination with letrozole): 1500 mg orally once a day continuously.

Comments:
-Consult the manufacturer product information for capecitabine and letrozole dosing recommendations.
-HER2-positive metastatic breast cancer patients should have disease progression on trastuzumab prior to initiation of treatment with this drug in combination with capecitabine.

Uses:
-In combination with capecitabine for treatment of patients with advanced or metastatic breast cancer whose tumors overexpress HER2 and who have received prior therapy including an anthracycline, a taxane, and trastuzumab.
-In combination with letrozole for treatment of postmenopausal women with hormone receptor-positive metastatic breast cancer that overexpresses the HER2 receptor for whom hormonal therapy is indicated.

Renal Dose Adjustments

Data not available regarding dosage adjustments; however, the pharmacokinetics of this drug are unlikely to be affected given that less than 2% of an administered dose is eliminated by the kidneys.

Liver Dose Adjustments

PRE-EXISTING MILD TO MODERATE HEPATIC IMPAIRMENT (CHILD-PUGH A/B): Data not available.

PRE-EXISTING SEVERE HEPATIC IMPAIRMENT (CHILD-PUGH C): Reduce dose:
-HER2-Positive Metastatic Breast Cancer (in combination with capecitabine): 750 mg/day.
-Hormone Receptor-Positive, HER2-Positive Metastatic Breast Cancer (in combination with letrozole): 1000 mg/day

SEVERE HEPATOTOXICITY OCCURS DURING THERAPY: Permanently discontinue treatment.

Comments: Dose adjustment recommendations are based on pharmacokinetic studies; there are no clinical data available.

Dose Adjustments

CONCOMITANT USE WITH STRONG CYP450 3A4 INHIBITORS AND/OR STRONG CYP450 3A4 INDUCERS: Avoid concomitant use if possible. Dose adjustment recommendations are based on pharmacokinetic studies; there are no clinical data available.
CONCOMITANT USE WITH STRONG CYP450 3A4 INHIBITOR: Reduce dose to 500 mg/day; allow washout period of approximately 1 week before upward adjustment of this drug to the usual recommended dose if inhibitor discontinued.
CONCOMITANT USE WITH STRONG CYP450 3A4 INDUCER: Gradually up-titrate dose based on tolerability; decrease dose back to the usual recommended dose if inducer discontinued.
-HER2-Positive Metastatic Breast Cancer (in combination with capecitabine): Increase dose up to 4500 mg/day.
-Hormone Receptor-Positive, HER2-Positive Metastatic Breast Cancer (in combination with letrozole): Increase dose up to 5500 mg/day.

GRADE 2 or GREATER DECREASED LEFT VENTRICULAR EJECTION FRACTION (LVEF) OR LVEF THAT DROPS BELOW INSTITUTION'S LOWER LIMIT OF NORMAL: Discontinue treatment; may restart at reduced dose after a minimum of 2 weeks if LVEF recovers to normal and patient is asymptomatic.
Reduced Doses:
-HER2-Positive Metastatic Breast Cancer (in combination with capecitabine): 1000 mg/day
-Hormone Receptor-Positive, HER2-Positive Metastatic Breast Cancer (in combination with letrozole): 1250 mg/day

GRADE 3 OR GRADE 1 or 2 DIARRHEA WITH COMPLICATING FEATURES (moderate to severe abdominal cramping, Grade 2 or greater nausea or vomiting, decreased performance status, fever, sepsis, neutropenia, frank bleeding, or dehydration): May reintroduce at lower dose when diarrhea resolves to Grade 1 or less.
Reduced Doses:
-HER2-Positive Metastatic Breast Cancer Patients (in combination with capecitabine): 1000 mg/day
-Hormone Receptor-Positive, HER2-Positive Metastatic Breast Cancer Patients: 1250 mg/day
GRADE 4 DIARRHEA: Permanently discontinue treatment.

OTHER TOXICITIES, GRADE 2 or GREATER: May consider discontinuation or interruption of dosing; may restart at the usual recommended dose when toxicity improves to Grade 1 or less.
IF TOXICITY RECURS: Reduce dose:
-HER2-Positive Metastatic Breast Cancer (in combination with capecitabine): 1000 mg/day
-Hormone Receptor-Positive, HER2-Positive Metastatic Breast Cancer Patients: 1250 mg/day

Precautions

US BOXED WARNING: HEPATOTOXICITY
Hepatotoxicity has been observed in clinical trials and postmarketing experience. The hepatotoxicity may be severe. Deaths have been reported; however, causality of the deaths is uncertain.

Safety and efficacy have not been established in patients younger than 18 years.

Consult WARNINGS section for additional precautions.

Dialysis

Data not available; however, hemodialysis would not be expected to be an effective method to enhance drug elimination because this drug is not significantly renally excreted (less than 2%) and is highly bound to plasma proteins (more than 99%).

Other Comments

Administration Advice:
-Administer this drug at least 1 hour before or 1 hour after food, and at the same time in relation to food intake (e.g., 1 hour before a meal every day) to minimize variability in the individual patient.
-Administer the daily dose all at once; do not divide the dose.
-In the event of a missed dose, advise patients to skip those doses and to resume dosing with the next scheduled daily dose.

Storage Requirements:
-Do not store above 30 degrees Celsius.

General:
-The maximum oral dose administered in clinical trials is 1800 mg once a day.
-This drug is not indicated in the adjuvant setting.
-Overdosage: No known antidote; hemodialysis is not expected to be an effective method to enhance drug elimination.
-HER2 (ErbB2) overexpressing tumors are defined by a score of 3+ using an immunohistochemistry-based assessment (IHC3+), IHC2+ with gene amplification, or gene amplification alone.

Monitoring:
-Cardiovascular: Cardiac function, including left ventricular ejection fraction (prior to treatment initiation and approximately every 8 to 12 weeks during treatment); QTc prolongation (prior to and during treatment)
-Gastrointestinal: Change in bowel patterns and diarrhea (regularly during treatment)
-Hematological: Complete blood count (regularly during treatment when this drug is administered in combination with paclitaxel)
-Hepatic: Liver function/transaminases, bilirubin, alkaline phosphatase (prior to treatment initiation, every 4 to 6 weeks during treatment, and as clinically indicated)
-Respiratory: Pulmonary symptoms indicative of interstitial lung disease or pneumonitis (regularly during treatment)

Patient Advice:
-Avoid drinking grapefruit juice and taking any grapefruit products during treatment with this drug.
-Avoid potentially dangerous activities such as driving and operating machinery until you know how this drug affects you.

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