Learning Objective

• Introduction and classification of sterile dosage forms
• Different routes of injection administration

Sterile, pyrogen-free preparations intended to be administered by way of injections are called parenterals. The term “parenteral” is derived from the Greek terms para (outside or other than) and enteron (intestine) and denotes routes of administration other than the oral route.

The various sterile dosage forms are small and large volume injectables, irrigation fluids, dialysis solutions, biological preparations including vaccines, toxoids, antitoxins and ophthalmic preparations. Sterility is a prerequisite for parenterals because these preparations come into direct contact with the internal body fluids or tissues, where infection can easily occur.

Pyrogens are metabolic endotoxin products of microorganisms, which are lipid substances associated with a polysaccharide or peptide carrier molecule. If these are injected, they increase the body temperature, cause body ache and cutaneous vasoconstriction and increase the arterial blood pressure. Pyrogens are highly thermostable, water soluble and chemically inert. However, they are nonvolatile in nature, which provides a way for their removal.

Table 8.1 provides the differences between exotoxins and endotoxins.

The parenteral routes are used when rapid drug action is required, when the patient is noncooperative or unconscious and unable to accept oral medication, or when the drug is ineffective by other routes. Most of the injections are administered by the physician or nurse in the course of medical treatment, except insulin, which can be self-administered by the patient.

 

Table 8.1 Differences between Bacterial Exotoxins and Endotoxins

Sl. No	Exotoxins	Endotoxins
1.	Excreted by both Gram-positive and Gram-negative bacteria into the surrounding medium	An integral part of the outer lipopolysaccharide layer of Gram-negative bacteria and is liberated upon disintegration of the bacterial cell wall
2.	Protein in nature	Lipopolysaccharide in nature
3.	Heat sensitive	Heat stable
4.	Specific receptors on host target cells	Diverse range of host cells and systems affected
5.	Specific effects in host by treating with formalin	Diverse range of effects in host