Morphine is a pain medication of the opiate variety which is found naturally in a number of plants and animals. It acts directly on the central nervous system (CNS) to decrease the feeling of pain. It can be taken for both acute pain and chronic pain. It is frequently used for pain from myocardial infarction and during labour. It can be given by mouth, by injection into a muscle, by injecting under the skin, intravenously, into the space around the spinal cord, or rectally. Maximum effect is around 20 minutes when given intravenously and 60 minutes when given by mouth, while duration of effect is 3–7 hours. Long-acting formulations also exist.