Medicine Name: Libset Tablet. Composition: Lapatinib (250mg). Side Effects: Abdominal pain Back pain Breathing problems Constipation Cough Diarrhea Fatigue Headache Hot flashes Increased bilirubin in the blood Insomnia difficulty in sleeping Joint pain Liver damage Loss of appetite Mucosal inflammation Nausea Pain in extremities Rash Stomatitis Inflammation of the mouth Vomiting Weakness Weight gain.