Indications: Breast cancer:

Treatment of human epidermal growth receptor type 2 (HER2) overexpressing advanced or metastatic breast cancer (in combination with capecitabine) in patients who have received prior therapy (with an anthracycline, a taxane, and trastuzumab).

HER2 overexpressing hormone receptor–positive metastatic breast cancer in postmenopausal women where hormone therapy is indicated (in combination with letrozole).

Limitations of use: Patients should have disease progression on trastuzumab prior to initiation of treatment with lapatinib in combination with capecitabine.

Cautions: low gastric pH (reduced absorption); susceptibility to QT-interval prolongation (including concomitant use of drugs that prolong QT-interval and electrolyte disturbances); monitor left ventricular function; monitor for pulmonary toxicity; monitor liver function before treatment and at monthly intervals.

Note: This medication is in a class the Institute for Safe Medication Practices (ISMP) includes among its list of drug classes which have a heightened risk of causing significant patient harm when used in error.

Contra-indications: Hypersensitivity to lapatinib or any component of the formulation.

Hepatic impairment: caution in moderate to severe impairment (metabolism reduced).

Renal impairment: caution in severe impairment (no information available)

Pregnancy: avoid unless potential benefit outweighs risk (toxicity in animal studies).

Side Effects: anorexia, diarrhoea (treat promptly), decreased left ventricular ejection fraction, cardiac failure (fatal cases reported), malaise, rash, nail disorders, hyperbilirubinaemia, hepatotoxicity (discontinue permanently if severe). less commonly: interstitial lung disease; respiratory failure (including fatal cases) also reported.

Dose: In combination with capecitabine;

ADULT over 18 years; 1.25 g once daily

In combination with an aromatase inhibitor.

ADULT over 18 years:, 1.5 g once daily

Always take at the same time in relation to food: either one hour before or one hour after food. Patients should report unexpected changes in bowel habit.