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Related Experiment Videos

The interaction of preservatives with polyhydroxyethylmethacrylate (polyHEMA).

N E Richardson, D J Davies, B J Meakin

    The Journal of Pharmacy and Pharmacology
    |August 1, 1978
    PubMed
    Summary

    Contact lens preservatives interact differently with poly(2-hydroxyethyl methacrylate) (polyHEMA). Benzalkonium chloride and chlorhexidine gluconate show high affinity, with chlorhexidine interaction reversibility influenced by additives.

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    CONGENITAL RADIO-ULNAR SYNOSTOSIS.

    British medical journal·2010

    Area of Science:

    • Ophthalmic materials science
    • Polymer chemistry
    • Pharmaceutical formulation

    Background:

    • Contact lens solutions utilize preservatives to prevent microbial contamination.
    • Poly(2-hydroxyethyl methacrylate) (polyHEMA) is a common hydrogel material for soft contact lenses.
    • Understanding preservative-material interactions is crucial for contact lens safety and efficacy.

    Purpose of the Study:

    • To investigate the interaction mechanisms between common contact lens preservatives and polyHEMA.
    • To characterize the binding isotherms and reversibility of these interactions.
    • To assess the influence of formulation adjuvants on preservative-polyHEMA interactions.

    Main Methods:

    • Sorption isotherm studies were performed to quantify preservative uptake by polyHEMA.

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  • Reversibility of preservative binding was tested under various conditions (e.g., presence of electrolytes, surfactants).
  • The effect of formulation adjuvants (electrolytes, hydrophilic polymers) on interactions was evaluated.

    • Main Results:

    • Benzalkonium chloride and chlorhexidine gluconate exhibited high-affinity binding to polyHEMA.
    • Benzalkonium chloride interaction was reversible, while chlorhexidine interaction required electrolytes or surfactants for reversibility.
    • Chlorbutol showed linear, reversible isotherms; thiomersal did not interact above pH 5.0.
    • Formulation adjuvants enhanced chlorhexidine-polyHEMA interactions, leading to higher-than-predicted binding.

    Conclusions:

    • Preservative-polyHEMA interactions vary significantly, impacting their behavior in contact lens solutions.
    • Chlorhexidine gluconate's interaction profile suggests potential for sustained release or accumulation in polyHEMA lenses.
    • Formulation components can modulate preservative binding, necessitating careful consideration in contact lens solution design.