Parenterals are sterile dosage forms intended for administration by injection through the skin or mucous membranes. They bypass the gastrointestinal tract, making them essential for emergency care, unconscious patients, and drugs that are poorly absorbed orally. Parenteral preparations must be sterile, pyrogen-free, particle-free, and safe for direct entry into the body.
Why Parenterals Are Needed
- For rapid onset of action
- For patients who cannot take oral medication
- When the drug is destroyed by stomach acid or first-pass metabolism
- Precise and controlled drug delivery
- Useful for fluids, electrolytes, and nutritional therapy
Disadvantages of Parenterals
- Pain or discomfort at injection site
- Risk of infection if not sterile
- Requires trained personnel
- More expensive than oral dosage forms
- Difficult to reverse the dose once given
Routes of Parenteral Administration
1. Intravenous (IV)
- Drug injected directly into the bloodstream
- Immediate effect
- Suitable for fluids, electrolytes, and emergency medicines
2. Intramuscular (IM)
- Injected into large muscles (deltoid, gluteus)
- Moderate absorption rate
3. Subcutaneous (SC)
- Injected into fatty tissue beneath the skin
- Used for insulin, vaccines, and small-volume injections
4. Intradermal
- Injected into the dermal layer
- Used for sensitivity tests and certain vaccines
5. Specialized Routes
- Intrathecal
- Epidural
- Intra-articular
- Intra-cardiac (rare)
Types of Parenteral Preparations
- Injection solutions: Drug dissolved in water
- Dry powder for injection: Reconstituted before use
- Suspensions for injection: Insoluble particles in sterile vehicle
- Emulsions: Oil-in-water type used for nutrition and certain drugs
- Large Volume Parenterals (LVPs): >100 mL (IV fluids)
- Small Volume Parenterals (SVPs): <100 mL (vaccines, analgesics)
Formulation Requirements
- Sterility: No microbes
- Pyrogen-free: No fever-causing endotoxins
- Isotonicity: Match body fluids to avoid pain
- Proper pH: To prevent irritation or precipitation
- Stability: Chemical and physical stability ensured
Ingredients Used
- Vehicles: Water for Injection (WFI), oils for IM injections
- Buffering agents: Maintain pH
- Preservatives: Only for multi-dose vials (benzyl alcohol)
- Antioxidants: Prevent oxidation
- Tonicity adjusters: Sodium chloride, dextrose
Manufacturing Steps
- Raw material preparation
- Solution or suspension preparation
- Filtration
- Filling into sterile containers
- Sealing
- Sterilization (final or terminal)
- Inspection and labeling
Sterilization Methods
- Autoclaving: Moist heat, 121°C
- Dry heat sterilization: For oils and glassware
- Membrane filtration: For heat-sensitive drugs
- Radiation sterilization: Gamma radiation
- Gas sterilization: Ethylene oxide
Containers and Packaging
- Ampoules
- Vials (single or multi-dose)
- Pre-filled syringes
- Infusion bottles and bags
- Plastic collapsible bags for IV fluids
Quality Control Tests
- Sterility testing
- Pyrogen test (LAL test)
- Particulate matter testing
- pH measurement
- Assay of active ingredient
- Container integrity testing
Patient Counseling Points
- Explain purpose and expected effects of injection
- Monitor for pain, swelling, or allergic reactions
- Follow aseptic precautions if self-injecting (e.g., insulin)
- Store injections as per label (refrigerate if required)
- Never reuse needles or syringes
Detailed Notes:
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