Formulation of Injections

• Formulation of Injections involves selecting active ingredients, solvents, stabilizers, and preservatives to ensure sterility, stability, and bioavailability.
• Formulation of Injections ensures isotonicity, pH adjustment, and compatibility to maintain patient safety and therapeutic efficacy.
• Injections are sterile, pyrogen-free liquid preparations intended for parenteral administration.
• They can be solutions, suspensions, or emulsions, depending on the drug’s properties.

Components of Injectable Formulations:

1. Active Pharmaceutical Ingredient (API):

   • The drug substance is formulated to ensure stability, efficacy, and safety.
   • Example: Antibiotics, analgesics, or hormones.

2. Vehicle:

   • A medium in which the API is dissolved or suspended.
   • Aqueous Vehicles: Water for Injection (WFI) is the most commonly used.
   • Non-Aqueous Vehicles: Fixed oils (e.g., sesame oil), water-miscible solvents (e.g., polyethylene glycol) for drugs insoluble in water.

3. Additives:

   • Buffers: Maintain a stable pH (e.g., phosphate or citrate buffers).
   • Antioxidants: Prevent oxidation (e.g., ascorbic acid, sodium bisulfite).
   • Preservatives: In multi-dose vials to inhibit microbial growth (e.g., benzyl alcohol, phenol).
   • Chelating Agents: Improve stability by binding metal ions (e.g., EDTA).
   • Tonicity Adjusters: Ensure isotonicity with body fluids (e.g., sodium chloride, dextrose).

Types of Injections:

1. Intravenous (IV): Directly into the bloodstream; requires isotonicity and high sterility.
2. Intramuscular (IM): Administered into muscle tissue; can use oily or aqueous vehicles.
3. Subcutaneous (SC): Injected into the fat layer beneath the skin; requires small volumes.
4. Intradermal (ID): Administered into the dermis layer of skin; typically for vaccines or diagnostic purposes.

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