Parenteral dosage forms characteristics

Until recently, nonparenteral routes have failed to deliver sufficient quantities of ASO to be systemically therapeutic. The recent advent of novel oral delivery technologies, coupled with the increased tissue residence time for second-generation ASOs, allows oral delivery to achieve therapeutic levels for select systemic indications. This chapter will initially outline certain more conventional aspects of parenteral dosage forms, and then focus on formulation technologies that more specifically address local treatment. For the oral route, we will pass to the biopharmaceutic considerations for both local delivery to the gut and systemic delivery via absorption from solid dosage forms. Incumbent with the discussion on formulations is the need initially to overview the physico-chemical properties of ASOs, which in large part determine their biopharmaceutic characteristics. 

During the development of parenteral dosage forms, the formulator selects excipients that will provide a stable, efficacious, and functional product. The choice, and the characteristics of excipients should be appropriate for the intended purpose. 

The U.S. Pharmacopoeia (USP) classifies injections into five different types. The dosage form selected for a particular drug product is dependent upon the characteristics of the drug molecule (e.g., stability in solution, solubility, and injectability), the desired therapeutic effect of the product (e.g., immediate vs. sustained release), and the desired route of administration. Solutions and some emulsions (e.g., miscible with blood) can be injected via most parenteral routes of administration. 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. 

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