THE JOURNAL OF THE STOMATOLOGICAL SOCIETY,JAPAN
Online ISSN : 1884-5185
Print ISSN : 0300-9149
Original Article
Preparation and Drug-release Properties of Poly (lactic-co-glycolic acid) Microparticles Co-encapsulating Lidocaine and Capsaicin
OKABE SakiNAKAGAWA YasuhiroSATO YuWAKITA RyoMAEDA ShigeruIKOMA Toshiyuki
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2024 Volume 91 Issue 1 Pages 35-46

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Abstract

  The local anesthetic lidocaine exhibits an analgesic effect by inhibiting the activity of sodium-ion channels in nerve cells. However, intraoral application may also paralyse the motor nerves, resulting in biting of the lip, tongue, and buccal mucosa. Lidocaine has a short blood half-life of approximately 1.5 to 2 hours, and the extension of postoperative analgesic time is required. Therefore, in this study, lidocaine and capsaicin were co-encapsulated in biocompatible poly (lactic-co-glycolic acid) microparticles using an emulsion-solvent evaporation technique to achieve specific targeting of the sensory nerves. Capsaicin opens the TRPV1 channel, which is expressed exclusively on sensory nerve C fibers, enabling selective internalisation of lidocaine into sensory nerves. Microparticles with an average diameter of 3.4±0.3 μm had a smooth and uneven surface. The drug loading of lidocaine in PLGA was constant (≈4%), but that of capsaicin varied from 0.6 to 2.2%, depending on the initial loading amounts. The entrapment efficiency of capsaicin in PLGA was higher than that of lidocaine owing to differences in hydrophobicity. The glass-transition temperature of PLGA decreased depending on the drug loading, where the decrease was greater for capsaicin. In vitro studies showed a gradual release of both lidocaine and capsaicin over 10 h, with no initial burst. The release profiles of both drugs from PLGA microparticles followed the Higuchi model. Furthermore, kinetic analyses indicated that capsaicin was released from the PLGA microparticles at a faster rate than lidocaine.

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© 2024 The Stomatological Society, Japan
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