What can be used for eye drops in a rat? - briefly
Sterile isotonic saline, balanced salt solution, or commercially available ophthalmic lubricants (e.g., artificial tears) are appropriate for administering drops to a rat’s eye. Apply 1–2 µL per eye using a calibrated micropipette or fine dropper.
What can be used for eye drops in a rat? - in detail
When delivering ophthalmic solutions to laboratory rats, the vehicle must be sterile, isotonic, and physiologically compatible with the corneal epithelium. Commonly employed bases include:
- Balanced salt solution (BSS) – contains NaCl, KCl, CaCl₂, MgCl₂, glucose, and phosphate buffers; pH 7.2–7.4, osmolarity ≈ 300 mOsm/kg. Provides a neutral environment for most drugs and minimizes irritation.
- Phosphate‑buffered saline (PBS) – similar ionic composition to BSS; often used when the experimental compound is stable in phosphate buffers. Adjust pH to 7.0–7.4 and filter‑sterilize before use.
- Artificial tears (carboxymethylcellulose or hyaluronic acid formulations) – viscous agents that increase residence time on the ocular surface. Suitable for drugs requiring prolonged exposure; ensure preservative‑free preparations to avoid toxicity.
- Sterile isotonic saline (0.9 % NaCl) – simple, readily available medium for short‑acting agents. Verify pH (≈ 7.0) and add buffering agents if necessary.
- Commercial ophthalmic gels (e.g., methylcellulose‑based) – used for sustained‑release applications; verify compatibility with the test compound and avoid formulations containing benzalkonium chloride.
Key preparation considerations:
- Adjust pH to the range 6.8–7.6; extreme values can disrupt corneal integrity.
- Confirm osmolarity matches tear fluid to prevent epithelial edema.
- Filter through a 0.22 µm membrane and store at 2–8 °C; avoid repeated freeze‑thaw cycles.
- Use preservative‑free solutions for repeated dosing to prevent cumulative toxicity.
Administration technique:
- Restrain the animal gently, using a soft cloth or a purpose‑designed restrainer.
- Apply a calibrated micropipette or a 30‑gauge blunt cannula to deliver 5–10 µL per eye, avoiding direct contact with the cornea.
- Observe the animal for blinking or tearing; allow a brief pause before releasing restraint to ensure absorption.
Safety and quality control:
- Perform sterility checks on each batch (e.g., incubation on agar plates).
- Validate drug stability in the chosen vehicle under experimental conditions.
- Record the exact volume and time of each instillation to maintain reproducibility.