Pharmaceutical Preparations and Solubility

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.