Use Onpattro (Patisiran) 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.Patisiran is given as an infusion into a vein. A healthcare provider will give you this injection once every 3 weeks. This medicine must be given slowly, and the infusion can take about 80 minutes to complete. Tell your caregivers if you feel any burning, pain, or swelling around the IV needle when patisiran is injected. You may be given other medications to help prevent serious side effects or an infusion reaction. Your doctor may have you take vitamin A while you are using patisiran. Take only the amount of vitamin A your doctor has prescribed, especially if you are pregnant. An overdose of vitamin A can cause vision problems or other serious side effects. Call your doctor at once if you have vision problems (especially at night) while you are taking patisiran. Patisiran doses are based on weight. Your dose needs may change if you gain or lose weight. You may need frequent medical tests. Even if you have no symptoms, tests can help your doctor determine if this medicine is effective. You may also need frequent eye exams.