Vehicles Used in Parenteral Formulations
Vehicles used in parenteral formulations are the carriers or solvents used to dissolve or suspend active pharmaceutical ingredients (API) for injection. These vehicles must meet stringent quality standards to ensure sterility, safety, and compatibility with both the drug and the patient’s body. The following are the main types of vehicles used in parenteral preparations.
Vehicles Used in Parenteral Formulations
1. Aqueous Vehicles
Aqueous vehicles are the most commonly used solvents in parenteral products because of their ability to mix with biological fluids and their safety profile.
a) Water for Injection (WFI) USP
- Definition: Highly purified water used for injectables, which is subsequently sterilized during the final process.
- Specifications:
- USP Requirements: Must contain no more than 10 parts per million (ppm) of total solids.
- pH Range: 5.0–7.0.
- Preparation:
- WFI can be prepared through distillation or reverse osmosis to remove impurities.
- Storage: Stored in chemically resistant tanks to avoid contamination.
- Use: It serves as a solvent in the manufacturing of sterile drugs, which undergo terminal sterilization during packaging.
b) Bacteriostatic Water for Injection (BWFI)
- Definition: This type of water is used to prepare parenteral solutions under aseptic conditions.
- Key Features:
- It is not terminally sterilized but must meet USP sterility tests.
- Bacteriostatic Agents: May contain antimicrobial preservatives (e.g., benzyl alcohol) to inhibit bacterial growth.
- Available in containers ≤30 mL.
- Use: Suitable for multi-dose injections to maintain sterility during repeated use.
c) Sterile Water for Injection (SWFI)
- Definition: SWFI contains one or more bacteriostatic agents and is used in multi-dose containers.
- Key Features:
- Container Size: Multi-dose containers are limited to 30 mL or less.
- Solids Content: It may have higher solid content than WFI due to leaching from glass containers.
- Uses:
- Frequently used for washing wounds, surgical incisions, or body tissues.
- Provides a sterile medium for rinsing during surgeries.
d) Water-Miscible Vehicles
- Definition: These solvents are miscible with water and are used as part of the vehicle to enhance solubility and reduce hydrolysis of drugs.
- Examples:
- Ethyl Alcohol: Commonly used in cardiac glycosides to improve solubility.
- Propylene Glycol: Used to prevent hydrolysis and enhance drug stability.
- Glycerin: Acts as a stabilizer and solvent for some injectables.
- Use: These vehicles are essential for drugs that require improved solubility in aqueous media and for formulations sensitive to hydrolysis.
2. Non-Aqueous Vehicles
Non-aqueous vehicles are used for drugs that are either insoluble or unstable in water. These vehicles, mainly oils, ensure the controlled release of the drug and prolong absorption.
a) Fixed Oils
- Definition: These are vegetable-origin oils that are liquid, non-rancid, and resistant to oxidation. They contain unsaturated free fatty acids to ensure stability over time.
- Key Features:
- Viscosity and Absorption: Fixed oils slow down drug absorption, making them ideal for depot injections.
- Compatibility: Must be non-toxic, non-irritating, and free of contaminants.
- Examples of Fixed Oils:
- Peanut Oil: Often used in hormone-based therapies.
- Corn Oil: Known for its stability and resistance to rancidity.
- Cottonseed Oil: Used in depot-testosterone injections for slow release.
- Sesame Oil: Commonly used in injections due to its stability.
- Soybean Oil: Used in lipid emulsions for nutritional supplementation.
- Ethyl Oleate: Provides a less viscous option compared to vegetable oils.
- Isopropyl Myristate: Used for drugs that need enhanced absorption through tissues.
Conclusion
The choice of vehicle in parenteral formulations is critical to ensure drug stability, safety, and effectiveness. Aqueous vehicles, like WFI, SWFI, and BWFI, are preferred for water-soluble drugs, while water-miscible and non-aqueous vehicles like fixed oils are used for drugs that need improved solubility or prolonged action. The vehicle must also meet strict USP standards to ensure sterility and safety for patient use.
By carefully selecting and preparing these vehicles, pharmaceutical manufacturers can ensure the successful delivery of therapeutic agents through parenteral routes
MCQs on Vehicles Used in Parenteral Formulations
1. Aqueous Vehicles
- What is the pH range for Water for Injection (WFI) USP?
- a) 2.0 – 4.5
- b) 5.0 – 7.0
- c) 7.5 – 9.0
- d) 4.0 – 8.0
Answer: b) 5.0 – 7.0
- What is the maximum allowable total solids in WFI according to USP?
- a) 5 ppm
- b) 10 ppm
- c) 20 ppm
- d) 50 ppm
Answer: b) 10 ppm
- Which process is NOT used to prepare Water for Injection (WFI)?
- a) Distillation
- b) Reverse Osmosis
- c) Ultrafiltration
- d) Filtration
Answer: c) Ultrafiltration
- Bacteriostatic Water for Injection (BWFI) can be used in containers with what maximum volume?
- a) 10 mL
- b) 30 mL
- c) 50 mL
- d) 100 mL
Answer: b) 30 mL
- What is the primary purpose of bacteriostatic agents in BWFI?
- a) Improve drug solubility
- b) Maintain isotonicity
- c) Inhibit bacterial growth
- d) Enhance drug absorption
Answer: c) Inhibit bacterial growth
- Which of the following is used for washing wounds and surgical incisions?
- a) Water for Injection
- b) Sterile Water for Injection
- c) Bacteriostatic Water for Injection
- d) Glycerin
Answer: b) Sterile Water for Injection
- Why do multi-dose containers of SWFI have higher solid content compared to WFI?
- a) Due to contamination
- b) Because of glass leaching
- c) Intentional addition of preservatives
- d) To enhance drug solubility
Answer: b) Because of glass leaching
- Which solvent is commonly used with cardiac glycosides to improve solubility?
- a) Propylene glycol
- b) Ethyl alcohol
- c) Glycerin
- d) Water
Answer: b) Ethyl alcohol
2. Non-Aqueous Vehicles
- Which of the following is NOT a non-aqueous vehicle?
- a) Corn oil
- b) Sesame oil
- c) Water for Injection
- d) Peanut oil
Answer: c) Water for Injection
- What is the primary advantage of fixed oils in parenteral formulations?
- a) Improve drug solubility
- b) Provide controlled drug release
- c) Enhance isotonicity
- d) Increase sterility
Answer: b) Provide controlled drug release
- Which oil is commonly used in testosterone depot injections?
- a) Soybean oil
- b) Cottonseed oil
- c) Sesame oil
- d) Corn oil
Answer: b) Cottonseed oil
- Which fixed oil is known for its high stability and resistance to rancidity?
- a) Corn oil
- b) Ethyl oleate
- c) Isopropyl myristate
- d) Glycerin
Answer: a) Corn oil
- Which of the following is used for parenteral formulations that require enhanced tissue absorption?
- a) Ethyl oleate
- b) Isopropyl myristate
- c) Propylene glycol
- d) Glycerin
Answer: b) Isopropyl myristate
- What is the main characteristic of oils used in parenteral formulations?
- a) High viscosity
- b) Resistance to rancidity
- c) High water content
- d) Rapid drug release
Answer: b) Resistance to rancidity
3. Water-Miscible Vehicles
- What is the role of water-miscible vehicles in parenteral products?
- a) Improve drug stability and solubility
- b) Enhance absorption in the gastrointestinal tract
- c) Maintain sterility during administration
- d) Control drug release over time
Answer: a) Improve drug stability and solubility
- Which of the following is an example of a water-miscible vehicle?
- a) Propylene glycol
- b) Corn oil
- c) Isopropyl myristate
- d) Water for Injection
Answer: a) Propylene glycol
- Which solvent is commonly used to reduce hydrolysis of drugs?
- a) Glycerin
- b) Ethyl alcohol
- c) Propylene glycol
- d) Sodium chloride
Answer: c) Propylene glycol
- Which water-miscible vehicle is also used as a stabilizer for injections?
- a) Ethyl alcohol
- b) Glycerin
- c) Corn oil
- d) Water for Injection
Answer: b) Glycerin
- What is the main benefit of using ethyl alcohol in parenteral products?
- a) Acts as a buffer
- b) Increases viscosity
- c) Improves solubility
- d) Provides calories
Answer: c) Improves solubility
4. General Questions on Vehicles
- What is the key requirement for all vehicles used in parenteral formulations?
- a) Must be viscous
- b) Must be isotonic
- c) Must be sterile and free of pyrogens
- d) Must contain preservatives
Answer: c) Must be sterile and free of pyrogens
- Why are bacteriostatic agents not used in large volume parenterals (LVP)?
- a) They interfere with drug action
- b) They are toxic in large doses
- c) They reduce drug solubility
- d) They make solutions unstable
Answer: b) They are toxic in large doses
- Which vehicle type is preferred for drugs that are unstable in water?
- a) Aqueous vehicles
- b) Non-aqueous vehicles
- c) Isotonic vehicles
- d) Buffer solutions
Answer: b) Non-aqueous vehicles
- What happens if non-sterile water is used in parenteral formulations?
- a) Drug solubility increases
- b) Preservatives become ineffective
- c) Risk of microbial contamination increases
- d) Drug absorption is enhanced
Answer: c) Risk of microbial contamination increases
These 23 MCQs cover all essential aspects of vehicles used in parenteral formulations, including aqueous and non-aqueous vehicles, their properties, uses, and specifications. They will help you prepare effectively for pharmacy-related competitive exams such as GPAT, Drug Inspector, and Pharmacist exams.
Also, Visit:
B. Pharma Previous Year Question Paper
1 thought on “Vehicles Used in Parenteral Formulations”