Atorvastatin 20mg tablets are indicated for lowering cholesterol levels to reduce the risk of cardiovascular disease, contraindicated in patients with active liver disease or pregnancy, may cause side effects such as muscle pain, liver enzyme abnormalities, and gastrointestinal disturbances, and can interact with medications like certain antibiotics, antifungals, and other cholesterol-lowering agents, potentially increasing the risk of myopathy or rhabdomyolysis.