Parenteral dosage forms are those that are injected or infused into the body, bypassing the digestive system. This means they are typically administered through a variety of routes, including intravenously (IV), intramuscularly (IM), and subcutaneously (SC).

There are several types of parenteral dosage forms, including:

1. Solutions: These are clear, liquid formulations that are administered as injections. They typically contain water, saline or other agents, and active pharmaceutical ingredients.

2. Suspensions: These are parenteral formulations where an insoluble drug is dispersed in a liquid medium, creating a heterogeneous mixture. They typically require shaking prior to administration.

3. Emulsions: These are parenteral formulations in which an oil-based component is dispersed and stabilized in an aqueous phase. They offer advantages over solutions, including greater stability for certain drugs.

4. Powders: These are parenteral formulations that are typically lyophilized (freeze-dried) and reconstituted with sterile water or saline prior to injection.

Parenteral dosage forms offer several advantages over other routes of administration. For example, they can bypass the digestive system entirely, allowing for faster and more consistent absorption of drugs. Additionally, they allow for more precise dosing and can be easily administered in a hospital or clinical setting.

However, parenteral dosage forms also come with several disadvantages. They are typically more expensive than other routes of administration and require specialized training and equipment to administer safely. They can also pose a greater risk of infections or other adverse reactions due to their direct contact with the bloodstream.