Lontif 400mg Tablet MR is used for the management of asthma and chronic obstructive pulmonary disease (COPD). It contains Theophylline, which works by relaxing the airway in the lungs and making it easier to breathe. In some cases, you may experience side effects such as nausea, vomiting, restlessness, tremors, headache, muscle cramps, and increased heart rate. Before taking this medicine, you should tell your doctor if you are allergic to any of its components or if you are pregnant/breastfeeding, and about all the medications you are taking and pre-existing medical conditions.