Parenteral is derived from the two words ‘‘para’’ and ‘‘enteron’’ meaning to avoid the intestine. Parenteral articles are defined According to the USP 24/NF19 ‘‘as those preparations intended for injection through the skin or other external boundary tissue, rather than through the alimentary canal, so that the active substances they contain are administered using gravity or force directly into a blood vessel, organ, tissue, or lesion. An injection is a preparation intended for parenteral administration and/or for constituting or diluting a parenteral article prior to administration.’’ Parenteral drug administration is an attractive route of administration when oral administration is contraindicated, and it has been traditionally used in institutional settings.
Advantages and Disadvantages of Parenteral Products: The advantages and disadvantages of parenteral drugs and administration are shown in Table 2. Generally, parenterally administered drugs are advantageous because they can provide rapid and reliable drug systemic effects, long-term drug delivery, and targeted drug delivery. The disadvantages of parenteral products are predominately associated with safety issues related to infection and thrombosis, tissue damage and/or pain upon injection, and the use of requirements for specific equipment, devices, and techniques.
| Advantages | Disadvantages |
|---|---|
| Useful for patients who cannot take drugs orally | More expensive and costly toproduce |
| Useful for drugs that require a rapid onset of action (primarily intravenous administration) | Potential for infection at site of injection Potential for sepsis |
| Useful for emergency situations | Potential for thrombophlebitis |
| Useful for providing sustained drug dilivery (implants, intramucular depot injections) | Potential for fluid overload and Potential for air embilism |
| Can be used for self-dilivery of drugs (subcutaneous) | Potential for extravasation |
| Useful for drugs that are inactivated in the gastrointestinal tract or susceptible to first-pass metabolism by the liver | Psychological distress by the patient Require specialized equipment, device, and techniques to prepare and administer drugs |
| Useful for injection of drugs directly into a tissue (targeted drug delivery) | Potential for pain upon injection Potential for tissue dammage upon injection |
| Usful for delivering fluids, electrolytes, or nutrients (total parenteral nutrition to patients) | Risk of needlestick injuries and exposure to blood-home pathogens by health care worker |
| Useful for providing precise drug delivery by intravenous injection or infusion utilizing pharmacokinetic lechniques Can be done in hospitals, ambulatory infusion centers, and in home health care | Increased morbidity associated with long-term vascular access devices Disposal of needles, syringes, and other infusion devices requires special consideration |
Type of Parenterals: Parenteral products can be divided into two general
classes According to the volume of the product. All parenteral products are sterilized and must meet all the requirements for sterility and particulate matter and must be pyrogen-free. Small-volume parenterals (SVP) or injections are 100 ml or less and can be provided as a single- or multidose product. In contrast, large-volume parenterals (LVP) are intended to be used intravenously as a single-dose injection and contain more than 100 ml of solution.
The U.S. Pharmacopoeia (USP) classifies injections into five different types. The dosage form selected for a particular drug product is dependent upon-1. the characteristics of the drug molecule (e.g., stability in solution, solubility, and injectability), (2) the desired therapeutic effect of the product (e.g., immediate vs. sustained release), and (3) the desired route of administration. (4)-Solutions and some emulsions (e.g., miscible with blood) can be injected via most parenteral routes of administration. (5)Suspensions and solutions that are not miscible with blood (e.g., injections employing oleaginous vehicles) can be administered via intramuscular or subcutaneous injection but should not be given intravenously. A SVP product is available for most of the major therapeut-ic classes of drug.
A ‘‘drug injection’’ is a liquid preparation that is composed of drug substances and or solutions. A ‘‘drug for injection’’ is a dry solid that upon the addition of a suitable vehicle (usually a vehicle in which the drug is stable and soluble) provides a solution that conforms to the requirements for an injection. Drugs for injection are often lyophilized or freeze dried to assist in the reconstitution of the solid. A ‘‘drug injectable emulsion’’ is a liquid preparation of a drug or drug substances dissolved in a suitable emulsion vehicle. A ‘‘drug injectable suspension’’ is a liquid preparation of solids suspended in a suitable vehicle. A ‘‘drug for injectable suspension’’ is a dry solid (often lyophilized) that is intended, upon the addition of a suitable vehicle, to yield a preparation that in all aspects meets the requirements for an injectable suspension.
LVPs are often administered via intravenous infusion in a large single-dose container. The therapeutic goal of these products is to provide electrolytes, body fluids, and nutrition. These solutions may or may not be isotonic with blood depending upon the concentration of the components, which include sodium chloride, dextrose, mannitol, Ringers (sodium, potassium, calcium, and chloride) and Lactated Ringers (calcium, potassium, sodium, and lactate), sodium bicarbonate, ammonium chloride, sodium lactate, fructose, alcohol, dextran, and amino acids.
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