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Assessment of ocular irritability of liposome preparations
K Taniguchi1, Y Yamamoto, K Itakura
1Research and Development Division, Rohto Pharmaceutical Co., Ltd., Osaka, Japan.
Abstract:
Ocular irritability of neutral or positively charged liposomes were assessed by the Draize test, histological examination and the rabbit blinking test. The mean total score (MTS) of the Draize test showed a slight increase immediately following instillation of liposome preparations. However, it did not exceed the "practically nonirritating level", and the MTS rapidly became less than the "nonirritating level". No corneal histological alteration was observed by optical microscopy following 9 instillations of each liposome preparation. Although the neutral liposome preparation failed to increase the rabbit blinking count, the positively charged liposome preparation did so to a significant degree. The neutral liposome preparation was confirmed not to give rise to ocular irritation. However, the positively charged liposome preparation may cause pain or unpleasantness following instillation.
Insights
Neutral liposomes show no ocular irritation in rabbit models. Positively charged liposomes may cause discomfort, indicating potential ocular side effects for charged formulations.
Area of Science:
- Ophthalmology
- Materials Science
- Pharmacology
Background:
- Liposomes are widely used drug delivery systems.
- Assessing the ocular safety of liposome formulations is crucial for ophthalmic applications.
- Surface charge can influence liposome-tissue interactions and potential irritation.
Purpose of the Study:
- To evaluate the ocular irritability of neutral and positively charged liposomes.
- To compare the safety profiles of different liposome charge types in vivo.
- To determine the potential for corneal damage and discomfort associated with liposome instillation.
Main Methods:
- Draize test for ocular irritation scoring.
- Histological examination of corneal tissues.
- Rabbit blinking test to assess discomfort.
- Instillation of neutral and positively charged liposome preparations in rabbit eyes.
Main Results:
- Mean total scores from the Draize test showed only a slight, transient increase, remaining within non-irritating levels.
- No corneal histological alterations were observed via optical microscopy after multiple instillations.
- Neutral liposomes did not affect rabbit blinking rates, while positively charged liposomes significantly increased blinking.
- Positively charged liposomes indicated potential for ocular discomfort or pain.
Conclusions:
- Neutral liposomes are confirmed as non-ocular irritants.
- Positively charged liposomes may induce discomfort, suggesting careful consideration for ophthalmic use.
- Liposome surface charge is a critical factor in determining ocular tolerability.