Pharmaceutical Preparations and Solubility

Study Notes

Preparation of Parenteral Products

Unstable drugs in solution can be prepared as a dry powder for reconstitution with a solvent at the time of administration or as a suspension.
If a drug is unstable in water, a solvent in which the drug is insoluble can be used instead.

Types of Injections

Aqueous solutions can be injected directly into the bloodstream.
Blood-immiscible liquids, such as oleaginous injections and suspensions, can interrupt the normal flow of blood and are generally restricted to non-IV administration.

Factors Affecting Onset and Duration of Action

The chemical form and physical state of the injection (solution or suspension) can affect the onset and duration of action.
Drugs that are very soluble in body fluids have a more rapid onset of action.
Aqueous solutions have a more rapid onset of action than oleaginous solutions.
Aqueous suspensions are more rapid-acting than oleaginous suspensions.

Repository or Depot Preparations

Long-acting injections are used to reduce the frequency of injections.
These preparations are designed to release the drug slowly over time.

General Procedure for Preparation of Parenteral Products

The preparation room must be free from particulate matter and microorganisms.
Laminar air flow systems and UV radiation can be used to remove dust and microorganisms.
Room walls and benches must be cleaned with antimicrobial agents.
Workers must wear sterilized clothes, disinfected gloves, and masks.

Steps Involved in Preparation

Cleaning and sterilizing all equipment and containers.
Purity of ingredients must be ensured.
Compounding of the preparation involves adding small quantities first and then larger quantities to form a solution.
Filtration using millipore membrane filters removes microorganisms.
Distribution of the preparation into final containers (bottles, ampoules, plastic bags).
Glass is preferred for containers due to its high temperature during sterilization.
Amber-colored glass is used for photo-labile drugs.

Sterilization of Parenteral Products

Sterilization is the process of killing or removing microorganisms.
Sterilization methods include dry or moist heat.

Preparation of Injections

Solutions and suspensions of drugs intended for injection are prepared in a similar manner to solutions and disperse systems.
Solvents or vehicles must meet special purity and other standards to ensure safety by injection.

Vehicles for Parenteral Products

Water is the vehicle of greatest importance for parenteral products and must meet USP specifications.
Water-miscible vehicles, such as ethyl alcohol, polyethylene glycol, and propylene glycol, can be used to solubilize certain drugs and reduce hydrolysis.
Examples of vehicles include Sterile Water for Injection, Sodium Chloride Injection, Bacteriostatic Water for Injection, Ringer's Injection, and Lactated Ringer Injection.

Description

Learn about preparing unstable drugs for administration, including reformulation into dry powders, suspensions, and solutions in various solvents. Understand the importance of solvent selection for drug stability.