Specialized parenteral routes

Abstract

Specialized parenteral routes consist in the administration of a drug by injection or infusion through the skin into tissues, tissue spaces, vessels, or body compartments that are not of frequently used in clinical practice but are, nevertheless, particularly useful in selected clinical situations. The word parenteral comes from the Greek para, which means ?outside of,? and enteron, which is referred to ?the intestine.? Hence, the word ?parenteral? is referred to all those routes other than the oral route. It is necessary to clarify, though, that in a medical and pharmaceutical context, the term is usually reserved to refer to the administration of drugs by injection or infusion directly into tissues, tissue spaces, vessels, or body compartments [1].Parenteral routes of administration may be classified into primary and secondary. While primary routes refer to the most commonly parenteral routes used in medical clinic, i.e., intravenous (IV), intramuscular (IM) and subcutaneous (SC), secondary routes refer to all those parenteral routes that are less used or that are only reserved for very specific cases or pathologies. Also known as specialized parenteral routes, they are employed when the direct administration to a specific region, tissue, or organ is necessary to achieve high drug levels at the site of action, almost immediately, such as is emergency situations, for diagnostic purposes, for the chemotherapy through the cerebrospinal fluid (when the blood-brain barrier limits drug delivery to the brain by systemic circulation), or to treat infections of the eye (when the treatment by topic route or systemic circulation is not effective), among other examples. In the next sections, we will describe some of the specialized parenteral routes most used in the clinical practice, their anatomical characteristics, particular uses, and some associated drawbacks.