Nyrin 50mg Injection is used to prevent the harmful effects of methotrexate (anticancer medicine). It is also used to treat overdose of methotrexate. Nyrin 50mg Injection is given as a slow injection into veins under the supervision of a doctor. Your doctor will decide what dose is necessary and how often you need to take it. This will depend on what you are being treated for and may change from time to time. You should take it exactly as your doctor has advised. Taking it in the wrong way or taking too much can cause very serious side effects. Injection site reactions (pain, swelling, redness) are common side effects of this medicine. If these bother you or appear serious, let your doctor know. There may be ways of reducing or preventing them. Regular blood tests are required to check your blood cells and serum methotrexate concentration in blood. Before taking it, tell your doctor if have seizures, liver, or kidney problems or are taking any medicines to treat infections. Many other medicines can affect, or be affected by, this medicine so let your healthcare team know all medications you are using, especially phenytoin for your seizures. To make sure it is safe for you, let your doctor know if you are pregnant or breastfeeding before taking this medicine.