Many painkillers can be given by injection, either into a muscle or more usually under the skin (subcutaneously).
This involves using a small portable pump known as a syringe driver to give a continuous dose of a drug or drugs into a fine needle or plastic tube called a cannula placed just under the skin.
Intravenous infusion using a patient-controlled analgesia (PCA) pump
In hospital, for example after surgery, you may have a PCA pump to control your pain. A tube is placed in a vein in your arm or the back of your hand and connected to the pump, which has a handset that you press to give yourself a set dose of a painkiller, usually morphine. You can press the handset as often as needed to ensure your pain is controlled.