Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Intraperitoneal injection or IP injection is the injection of a substance into the peritoneum (body cavity). IP injection is more often applied to animals than humans. In general, it is preferred when large amounts of blood replacement fluids are needed, or when low blood pressure or other problems prevent the use of a suitable blood vessel for intravenous injection. In animals, IP injection is used predominantly in veterinary medicine and animal testing for the administration of systemic drugs and fluids due to the ease of administration compared with other parenteral methods.