An Injectable Oil-Based Depot Formulation of <i>N</i>-Acyloxymethyl Prodrug of Ropivacaine for Long-Acting Local Analgesia: Formulation Development and In Vitro/In Vivo Evaluation
<b>Objectives:</b> The development of novel long-acting injectables for local anesthetics is necessary to effectively manage the acute postoperative pain. The aim of this study was to prepare an injectable oil-based formulation of ropivacaine (ROP) prodrug (ropivacaine stearoxil, ROP-ST)...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-12-01
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| Series: | Pharmaceutics |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1999-4923/17/1/37 |
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| Summary: | <b>Objectives:</b> The development of novel long-acting injectables for local anesthetics is necessary to effectively manage the acute postoperative pain. The aim of this study was to prepare an injectable oil-based formulation of ropivacaine (ROP) prodrug (ropivacaine stearoxil, ROP-ST) and to investigate the pharmacokinetics and pharmacodynamics after injectable administration. <b>Methods:</b> A novel <i>N</i>-acyloxymethyl prodrug of ROP, i.e., ROP-ST, was synthesized and its physicochemical properties such as log P, solubility and stability characterized. A soybean oil-based depot of ROP-ST was prepared, and the in-vitro release of ROP-ST was evaluated using an “inverted-cup” method. Pharmacokinetic profiles and tissue retention properties were investigated after intramuscular administration of the formulation in rats. The analgesic efficacy was assessed via a von Frey monofilaments test by measuring the paw withdrawal thresholds. <b>Results:</b> The structure of ROP-ST was ascertained with clear <sup>1</sup>H NMR assignment and accurate mass-to-charge ratio. The high Log P value of ROP-ST (9.16) demonstrated extremely low aqueous solubility, but the prodrug is biolabile when in contact with plasma or liver esterase. Intramuscular injection of ROP-ST oil solution in rats provided a significantly higher mean residence time without a very clear plasma peak of ROP. In a postoperative pain model of rats, the injection of ROP-ST oil solution into the vicinity of the sciatic nerve in the right ankle effectively controlled the postoperative pain for at least 72 h. <b>Conclusions:</b> The injectable oil-based depot formulation of <i>N</i>-acyloxymethyl prodrug of ROP may provide a new opportunity of long-acting local analgesia for postoperative pain. |
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| ISSN: | 1999-4923 |