Use Casimersen (Amondys 45) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.Your doctor will perform blood tests to make sure you do not have conditions that would prevent you from safely using casimersen. Casimersen is given as an infusion into a vein, usually once per week. A healthcare provider will give you this injection. This medicine must be given slowly, and the infusion can take 35 to 60 minutes to complete. Your kidney function may need to be checked while you are using this medicine. Casimersen doses are based on weight. Your dose needs may change if you gain or lose weight.