Sterile Formulations in Pharmaceutics
Sterile formulations are dosage forms that must be completely free from microbes. These products directly enter sensitive areas of the body like blood, eyes, or internal tissues, so even a small contamination can cause serious infections. Because of this, sterile products are prepared with special care inside controlled environments.
Types of Sterile Formulations
- Injectables (Parenteral preparations)
- Eye drops (Ophthalmic solutions)
- Eye ointments (Ophthalmic ointments)
Injectables
Injectables (also called parenteral preparations) are sterile liquid or solid dosage forms that are given into the body using a syringe or IV infusion. They are used when fast action is needed or when the drug cannot be given by mouth.
Why Injectables Must Be Sterile
- They bypass normal body barriers
- Enter directly into blood, muscles, or tissues
- Any contamination can cause serious infections or death
Types of Injectables
- Injection: Liquid solution ready for use
- Injection for reconstitution: Dry powder that must be dissolved before use
- Suspension injections: Contain insoluble particles in liquid
- Emulsion injections: Oily and watery phases mixed together
- Large Volume Parenterals (LVP): More than 100 mL (e.g., IV fluids)
- Small Volume Parenterals (SVP): Up to 100 mL (e.g., vaccines, antibiotics)
Common Routes of Injection
- Intravenous (IV) – into a vein
- Intramuscular (IM) – into a muscle
- Subcutaneous (SC) – under the skin
- Intradermal – into the skin layers
Quality Requirements of Injectables
- Sterile (free from microbes)
- Pyrogen-free (should not cause fever)
- Free from particles
- Isotonic (same salt concentration as body fluids)
- Stable and safe
Eye Drops (Ophthalmic Solutions)
Eye drops are clear, sterile solutions meant to be placed into the eye. They must be extremely pure because eyes are very sensitive.
Characteristics of Eye Drops
- Must be sterile
- Free from particles
- Slightly acidic or neutral
- Isotonic to avoid irritation
- May contain preservatives (except in single-dose packs)
- Viscosity agents may be added to increase contact time with eye
Types of Eye Drops
- Antibiotic eye drops
- Anti-allergic eye drops
- Lubricating/tear substitutes
- Mydriatic and miotic solutions (for pupil dilation or constriction)
Packaging
- Plastic dropper bottles (multi-dose)
- Single-dose sterile containers (preservative-free)
Eye Ointments (Ophthalmic Ointments)
Eye ointments are sterile, semi-solid preparations applied to the eye. They stay longer on the eye surface, so they provide extended drug action compared to eye drops.
Characteristics of Eye Ointments
- Sterile and free from gritty particles
- Base should melt at body temperature
- Provide prolonged drug contact
- Usually packed in collapsible aluminium tubes
- Used mostly at bedtime as they can blur vision
Common Bases Used
- Petrolatum
- Mineral oil
- Lanolin
Types of Ophthalmic Ointments
- Antibiotic eye ointments (e.g., erythromycin)
- Anti-inflammatory ointments
- Lubricating/tear ointments
Why Sterility is Critical in Ophthalmic Preparations
- Eyes cannot fight infections easily
- Contamination may cause blindness
- Even small particles can scratch the cornea
Packaging and Storage of Sterile Formulations
- Stored in airtight, tamper-proof containers
- Kept away from heat and light
- Eye products are usually packed in dropper bottles or sterile tubes
- Injectables stored in ampoules, vials, prefilled syringes or IV bags
