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Lapatinib; Uses, Dosage, Side Effects, Interactions

Lapatinib is the ditosylate salt of lapatinib, a synthetic, orally-active quinazoline with potential antineoplastic activity. Lapatinib reversibly blocks phosphorylation of the epidermal growth factor receptor (EGFR), ErbB2, and the Erk-1 and-2 and AKT kinases; it also inhibits cyclin D protein levels in human tumor cell lines and xenografts. EGFR and ErbB2 have been implicated in the growth of various tumor types.

Lapatinib is a tyrosine kinase receptor inhibitor used in the therapy of advanced breast cancer and other solid tumors. Lapatinib therapy is associated with transient elevations in serum aminotransferase levels and rare instances of clinically apparent acute liver injury.

Mechanism of Action of Lapatinib

Lapatinib is a 4-anilino quinazoline kinase inhibitor of the intracellular tyrosine kinase domains of both epidermal growth factor receptor (HER1/EGFR/ERBB1) and human epidermal growth factor receptor type 2 (HER2/ERBB2)with a dissociation half-life of ≥300 minutes. Lapatinib inhibits ERBB-driven tumor cell growth in vitro and in various animal models. An additive effect was demonstrated in an in vitro study when lapatinib and 5-fluorouracil (the active metabolite of capecitabine) were used in combination in the 4 tumor cell lines tested. The growth inhibitory effects of lapatinib were evaluated in trastuzumab-conditioned cell lines. Lapatinib retained significant activity against breast cancer cell lines selected for long-term growth in the trastuzumab-containing medium in vitro. These in vitro findings suggest non-cross-resistance between these two agents.

Lapatinib Ditosylate is the ditosylate salt of lapatinib, a synthetic, orally-active quinazoline with potential antineoplastic activity. Lapatinib reversibly blocks phosphorylation of the epidermal growth factor receptor (EGFR), ErbB2, and the Erk-1 and-2 and AKT kinases; it also inhibits cyclin D protein levels in human tumor cell lines and xenografts. EGFR and ErbB2 have been implicated in the growth of various tumor types.

Lapatinib Indications

Indicated in combination with capecitabine for the treatment of patients with advanced or metastatic breast cancer whose tumors overexpress the human epidermal receptor type 2 (HER2) protein and who have received prior therapy including an anthracycline, a taxane, and trastuzumab.
Treatment of adult patients with breast cancer, whose tumors overexpress HER2 (ErbB2);
in combination with capecitabine for patients with advanced or metastatic disease with progression following prior therapy, which must have included anthracyclines and taxanes and therapy with trastuzumab in the metastatic setting in combination with trastuzumab for patients with hormone receptor-negative metastatic disease that has progressed on prior trastuzumab therapy is in combination with chemotherapy in combination with an aromatase inhibitor for postmenopausal women with hormone receptor-positive metastatic disease, not currently intended for chemotherapy.
The patients in the registration study were not previously treated with trastuzumab or an aromatase inhibitor. No data are available on the efficacy of this combination relative to trastuzumab in combination with an aromatase inhibitor in this patient population.
Lapatinib is a tyrosine kinase receptor inhibitor used in the therapy of advanced breast cancer and other solid tumors. Lapatinib therapy is associated with transient elevations in serum aminotransferase levels and rare instances of clinically apparent acute liver injury.
Breast Cancer
Breast Cancer, Metastatic
Refractory, advanced Breast cancer
Refractory, metastatic Breast cancer

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Lapatinib Contraindications

Severe infection
Diabetes
Anemia
Decreased Blood Platelets
Severely Decreased Platelets
Decreased Neutrophils a Type of White Blood Cell
Peripheral neuropathy
Disease of Inadequate Blood Flow to the Heart Muscle
Abnormal heart rhythm
Heart Disease
Liver problems
Severe liver disease
High Amount of Bilirubin in the Blood
Abnormal liver function tests
Pregnancy
A mother who is producing milk and breastfeeding
Severely Decreased Levels of Neutrophils in the Blood

Dosage of Lapatinib

Strengths: 250 mg

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.

Side Effects of Lapatinib

The Most Common

Abdominal or stomach pain or tenderness
diarrhea
symptoms of heart problems (e.g., shortness of breath, swelling of the ankles or feet, chest pain, irregular heartbeat)
symptoms of liver problems (e.g., nausea, vomiting, abdominal pain, yellowing of the skin and eyes, itchy skin, dark urine)
symptoms of lung problems (e.g., shortness of breath or difficulty breathing, chest pain, cough)
symptoms of a severe allergic reaction (e.g., hives; difficulty breathing; swelling of the face, mouth, tongue, or 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

More Common

Acid or sour stomach
back pain
belching
cracked lips
diarrhea (mild)
dry skin
heartburn
indigestion
pain in the arms or legs
redness, swelling, or painful skin
scaling of the skin on the hands and feet
sores, ulcers, or white spots on the lips, tongue, or the inside of the mouth

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Rare

Black, tarry stools
body aches or pain
burning, numbness, tingling, or painful sensations
burning pain on urination
chest pain
chills
cough
difficult or labored breathing
ear congestion
fever
headache
loss of voice
lower back or side pain
nasal congestion
painful or difficult urination
pale skin
red, swelling, or painful skin

Drug Indications of Lapatinib

Lapatinib Ditosylate may interact with following drugs, supplements & may change the efficacy of drugs

calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
carbamazepine
carvedilol
cetirizine
corticosteroids (e.g., prednisone, dexamethasone)
cyclosporine
desipramine
dexamethasone
domperidone
doxorubicin
dronedarone
estrogens
everolimus
“gliptin” diabetes medications (e.g., linagliptin, saxagliptin, sitagliptin)
“glitazone” diabetes medications
hydrocortisone
loperamide
macrolide antibiotics (e.g., clarithromycin, erythromycin)
methadone
methotrexate
metronidazole
mirabegron
modafinil
nadolol
phenobarbital
phenytoin
prazosin
progesterone
propranolol
protein kinase inhibitors (e.g., pazopanib, sunitinib)
quinolone antibiotics (e.g., ciprofloxacin, norfloxacin, ofloxacin)
ranitidine
repaglinide
St. John’s Wort
serotonin antagonists (anti-emetics; e.g., granisetron, ondansetron)
sertraline
sotalol
“statin” anti-cholesterol medications (e.g., atorvastatin, lovastatin, simvastatin)
tacrolimus

Pregnancy Category

AU TGA Pregnancy Category: C
US FDA Pregnancy Category: D

Pregnancy

This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately. Women who may become pregnant should use contraception and avoid becoming pregnant while they are taking this medication.

Lactation

It is not known if lapatinib passes into breast milk. If you are a breastfeeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should breastfeeding. Breastfeeding while taking this medication is not recommended. The safety and effectiveness of using this medication have not been established for children.

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