What is Parenteral Administration? A Quick Guide.

Parenteral administration is a medical term that refers to any drug or medication delivery method that bypasses the digestive system and is directly injected into the body. This method is often used for patients who cannot take medications orally or when a quick and potent effect is needed. In this article, we will explore the different types of parenteral administration, common uses, advantages, disadvantages, and safety concerns.

Types of Parenteral Administration

There are several types of parenteral administration, including:

  • Intramuscular (IM): The drug is injected into a muscle using a needle and syringe.
  • Subcutaneous (SC): The drug is injected into the fatty tissue layer under the skin using a needle and syringe.
  • Intravenous (IV): The drug is directly administered into a vein using a needle and syringe connected to an IV line.
  • Intradermal (ID): The drug is injected into the top layer of skin using a needle and syringe.
  • Intra-articular (IA): The drug is injected into a joint using a needle and syringe.

Intramuscular (IM) Administration

IM administration is a common parenteral method used for administering vaccines, antibiotics, and some pain medications. The needle is typically inserted at a 90-degree angle into the muscle mass of the deltoid, gluteus, or quadriceps muscles. The absorption of the drug into the bloodstream is dependent on the vascularity of the muscle tissue.

Subcutaneous (SC) Administration

SC administration is commonly used for insulin, allergy shots, and other small doses of medication. The needle is generally shorter and thinner than those used for IM injections and is inserted at a 45-degree angle into the fatty tissue layer under the skin. The absorption of the drug via SC administration is slower than IM, but faster than oral administration.

Intravenous (IV) Administration

IV administration is a rapid and effective method to achieve high drug concentrations rapidly. It is usually reserved for emergency situations, critical care units, or specific procedures. The placement of the IV line requires specialized training, equipment, and careful attention to detail to avoid complications such as bloodstream infections or air embolisms.

Intradermal (ID) Administration

ID administration is often used for allergy testing, TB testing or small volumes of vaccines. The syringe is equipped with a very fine small-gauge needle and is inserted into the top layer of the skin- usually on the arm. The drug is slowly deposited into the dermis or epidermis layers under the skin, where it diffuses into the bloodstream.

Advantages of Parenteral Administration

Parenteral administration has several advantages, including:

  • Quick onset of action: Unlike oral medications, parenteral administration delivers drugs directly into the bloodstream or targeted tissue, allowing for a rapid onset of action.
  • Higher bioavailability: The digestive system is known to break down drugs before they reach the bloodstream, leading to less effective drug delivery. With parenteral administration, drugs bypass the digestive system, leading to a higher bioavailability than oral administration.
  • Avoidance of the first-pass effect: Oral medications go through the liver before reaching the bloodstream leading to changes in the drug’s chemical structure or total elimination. By choosing parenteral administration, this inhibition is avoided.

Disadvantages and Safety Concerns

Despite its benefits, parenteral administration can also have disadvantages and pose significant safety concerns, such as:

  • Risk of infection: Parenteral administration requires the use of needles and syringes, which can increase the risk of infections if not adequately sterilized. Proper aseptic techniques must always be employed during administration to ensure patient safety.
  • Pain and discomfort: Most patients experience some degree of discomfort or pain during the injection procedure, depending on the injection site and the drug’s characteristics.
  • Cost: Parenteral administration is considerably more expensive than oral administration, especially when specialized equipment and personnel are needed for IV administration.

Common Uses of Parenteral Administration

Parenteral administration is commonly used for the following reasons:

  • Emergency situations where the patient can’t take medications orally or when a quick and urgent response to the drug is needed.
  • Patient intolerance or allergy to medication taken orally.
  • To achieve therapeutic levels of the drug when oral administration is not an option (e.g., gastrointestinal complications or obstacles).
  • When a high bioavailability of the drug is required for effective therapy.


Parenteral administration is considered a safe and effective method for drug delivery in various medical situations. It has several benefits, such as high bioavailability and quick onset of action. However, it also presents some disadvantages such as possible infections, pain, and higher costs. It is essential to understand the different types of parenteral administration, how to administer safely, and when to use which route.


What is the difference between parenteral and enteral administration?

Parenteral administration is any drug or medication delivery method that bypasses the digestive system and is directly injected into the body, whereas enteral administration involves the administration of drugs through the oral, rectal, or sublingual route, where they are brought into contact with the GI tract and absorbed.

What are the risks associated with intravenous (IV) administration?

IV administration, while highly effective and commonly used in medical settings, presents several risks, such as infection, injury to blood vessels, bleeding or hematomas, embolism, and allergic reactions. All of these potential risks need to be evaluated to determine if the benefits of IV administration outweigh the potential risks.

What are the most common medications administered via parenteral administration?

Parenteral administration is commonly used for many types of medications, including antibiotics, chemotherapy, insulin, morphine, epinephrine, anesthetics, and vaccines. The choice of administration route is based on factors such as the patient’s health status, the medication’s intended effect, and the speed and duration of its action.


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3. Choudhury A, Garg SK, Singh GP, Kumar V, Kaul CL. A review of parenteral microemulsion drug delivery system. J Drug Target. 2014;22(4): 299-310.

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