Lapatinib Teva (Lapatinib)

Lapatinib acts on HER2‑driven tumor pathways and is used in advanced HER2‑positive cancers.

• HER2‑positive metastatic breast cancer: improves progression‑free survival when combined with other HER2‑targeted agents.
• HER2‑positive metastatic gastric cancer: contributes to disease control in combination regimens.
• HER2‑positive gastro‑oesophageal junction adenocarcinoma: used as part of multi‑drug therapy to delay tumor progression.

• Lapatinib reversibly inhibits the intracellular tyrosine kinase domains of epidermal growth factor receptor (EGFR/ErbB1) and HER2/neu (ErbB2). By blocking these receptors, it prevents downstream signaling through the MAPK and PI3K/AKT pathways, which reduces tumor cell proliferation, survival, and angiogenesis.

Lapatinib may cause a range of adverse reactions, from mild to severe.

Common Side Effects

• Diarrhea: frequent loose stools.
• Rash: skin irritation, often on the trunk.
• Nausea: feeling of sickness.
• Fatigue: reduced energy levels.
• Stomatitis: inflammation of the mouth lining.
• Elevated liver enzymes: increased ALT/AST.

Serious or Rare Side Effects

• Cardiac dysfunction: reduced left‑ventricular ejection fraction.
• Severe skin reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Hepatotoxicity: clinically significant liver injury.
• Interstitial lung disease: breathing difficulties and cough.
• Severe diarrhea leading to dehydration.
• Thromboembolic events: blood clot formation.

Before initiating therapy, clinicians should evaluate patient‑specific risk factors and monitor key parameters.

• Cardiac assessment: baseline and periodic echocardiograms for patients with cardiac history.
• Liver function: monitor ALT, AST, and bilirubin before and during treatment.
• Dermatologic monitoring: watch for severe rash or skin reactions.
• Gastrointestinal vigilance: assess for persistent diarrhea or dehydration.
• Drug interactions: review concomitant medications that affect CYP3A4.
• Store at ambient temperature: keep in original container, protect from moisture and direct sunlight.

Lapatinib’s metabolism involves CYP3A4, making it susceptible to drug‑drug interactions.

Major Interactions (Avoid)

• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): may markedly reduce exposure.
• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): can increase toxicity risk.

Moderate Interactions (Monitor Closely)

• Antacids containing aluminum or magnesium: may lower absorption; separate dosing by at least 2 hours.
• Warfarin: may enhance anticoagulant effect; monitor INR.
• Digoxin: potential increase in serum levels; observe for toxicity.
• Simvastatin: increased risk of myopathy; consider dose adjustment.
• Proton pump inhibitors: may modestly affect bioavailability.