Lapatinib Teva (Lapatinib)

Lapatinib is a targeted therapy that inhibits HER2 signaling in certain cancers.

• HER2‑positive metastatic breast cancer: used to inhibit tumor growth and improve progression‑free survival.
• HER2‑positive gastric cancer: employed to slow disease progression in advanced cases.
• Hormone‑receptor‑positive, HER2‑positive breast cancer (post‑menopausal): combined with letrozole to delay disease progression.

• Lapatinib reversibly binds to the intracellular tyrosine kinase domains of epidermal growth factor receptor (EGFR/ErbB1) and human epidermal growth factor receptor‑2 (HER2/ErbB2). By blocking autophosphorylation, it prevents activation of downstream signaling pathways such as MAPK and PI3K/AKT, which are responsible for cell proliferation, survival and angiogenesis in tumor cells. The inhibition also reduces cross‑talk with other receptor families, enhancing the anti‑tumor effect when used with chemotherapy or hormonal agents.

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

Common Side Effects

• Diarrhea: frequent loose stools, often mild to moderate.
• Rash: skin redness or papular eruptions, usually on trunk or limbs.
• Nausea: sensation of unease in the stomach, may be intermittent.
• Fatigue: feeling of tiredness that is not relieved by rest.

Serious or Rare Side Effects

• Hepatotoxicity: elevated liver enzymes or hepatitis requiring monitoring.
• Cardiac dysfunction: decreased left‑ventricular ejection fraction or heart failure.
• Severe skin reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Interstitial lung disease: breathing difficulties and pulmonary infiltrates.
• QT interval prolongation: risk of cardiac arrhythmias on ECG.

Before initiating therapy, clinicians should assess baseline organ function and monitor patients regularly.

• Liver monitoring: check hepatic enzymes before and during treatment.
• Cardiac assessment: evaluate left‑ventricular function prior to use and periodically thereafter.
• Skin evaluation: avoid in patients with a history of severe dermatologic disorders.
• QT monitoring: caution in patients with known QT prolongation or electrolyte abnormalities.
• Dose adjustment: consider reduced dosing in moderate hepatic impairment.
• Store at ambient temperature: keep in the original container, protect from moisture and heat.

Lapatinib can interact with several medicines, altering its effectiveness or safety.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): may increase Lapatinib exposure.
• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce therapeutic levels.
• Concurrent trastuzumab: may heighten risk of cardiac toxicity.

Moderate Interactions (Monitor Closely)

• Moderate CYP3A4 inhibitors (e.g., erythromycin, clarithromycin): require dose adjustment.
• Warfarin: monitor INR for potential anticoagulant effect changes.
• Digoxin: observe serum levels for possible concentration increase.