Parenteral: Definition & Medical Uses

Instructor: Zona Taylor

Zona has taught Nursing and has a master's degree in Nursing Education and Maternal-Infant Nursing from University of Maryland Baltimore.

This lesson provides the definition of the word parenteral and discusses the most commonly used routes of administration that fall into that category. We'll also give examples of their use and application.

That Medication's Going Where?

Our exposure to needles comes early in life. From multiple baby shots to nearly automatic IV fluids in an ambulance, the use of needles to put medicine, blood, or fluids into a patient is common place in the world of health care.

You notice how they sometimes let you take your medicine by mouth? That's called the 'oral' route of giving a medicine. There are a number of routes by which medications are administered. The most common are:

  • oral (by mouth)
  • parenteral (by injection)
  • topical (on the skin)

In the medical world, parenteral refers to administering medications without going through the digestive system. The word 'parenteral' comes from the roots 'para-', or 'outside of', and '-enteral' which refers to the alimentary, or digestive, system. When needles are used to administer medications and fluids, it is by the parenteral route.

Types of Parenteral Routes

Let's look at the most common parenteral routes of drug administration.

Intravenous

Medicines or fluids that go directly into the patient's vein are being given by the intravenous (IV) route. Many medications, fluids, and blood products are administered intravenously. Fluids may go in slowly and continuously for many hours using electronic IV pumps to control the rate. Some medicines can be injected directly into the vein or IV line over just a minute or so, while others are given for 30-120 minutes every few hours.

For patient's whose digestive system will not digest or absorb nutrients properly, we give them all the nutrients they need through a special kind of IV call TPN, or total parenteral nutrition. TPN is personalized to the patient's condition and requires frequent blood tests to see if the 'recipe' needs to be changed.

IV (intravenous) line in place in hand
IV in back of hand,intravenous

Most IV lines are flexible, plastic tubes called catheters. Some of these catheters are only one or two inches long. Others are much longer and are inserted into a vein in the upper arm and extended all the way to the entrance of the heart. These are call Peripherally Inserted Central Catheters, or PICC lines. Their intended use is for long-term administration of IV fluids or IV medications. Patients sometimes go home with a PICC line in place and learn to administer their own IV antibiotics or TPN.

Giving blood to a patient is done intravenously but the process is somewhat different. In order to give a patient blood, the size of the needle and catheter inserted must be large enough to accommodate the red blood cells (the largest of the cells floating in the bloodstream) without breaking (lysing) them. Blood products most frequently administered are packed red blood cells (PRBC) and whole blood. Other components that can be administered include platelets and fresh frozen plasma. All blood products are dripped in over a few hours.

Intraosseous

Another parenteral route is intraosseous infusion, which is injection of medication into the bone marrow. It is an indirect route to intravenous access because the bone marrow drains directly into the venous system. This route is occasionally used for drugs and fluids in emergency medicine and pediatrics when intravenous access is difficult and the need is immediate.

Intramuscular

Most of us know that we don't like getting medicine by the intramuscular (IM) route because it can feel pretty uncomfortable. This is using a needle to put the medicine into a muscle. Other terms for IM include hypodermic injection, a 'shot', or in England it may be called a 'jab'. Common muscles used are the deltoid muscle in the upper arm, a thigh muscle in children, or in a buttock muscle in older children and adults.

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