Dexmedetomidine (12.5 μg/mL) improves tissue distribution, anesthetic action, and hemodynamic effects of lidocaine after palatal infiltration in rats

Dexmedetomidine hydrochloride (DEX) is a α₂-adrenergic receptor agonist that causes vasoconstriction by acting on α_2B-adrenergic receptors in peripheral blood vessels. The authors aimed to determine the influence of DEX on tissue distribution, anesthetic action, and hemodynamic effects of lidocaine in rats. The investigators injected indigo carmine-containing ¹⁴C-labeled lidocaine hydrochloride (2 %) without and with 3.1, 12.5, or 50 μg/mL DEX or 10 μg/mL epinephrine into the right palatal mucosa mesial to the maxillary first molar of specific pathogen-free male Wistar rats. Autoradiography and liquid scintillation counting were performed to evaluate ¹⁴C-labeled lidocaine concentrations in the palatal mucosa, maxillary bone, maxillary nerve, and peripheral blood. Somatosensory-evoked potentials were measured to analyze anesthetic action, and blood pressure and pulse rate were measured to compare hemodynamic effects. DEX extended the tissue distribution of lidocaine in a concentration-dependent manner. Lidocaine with 12.5 μg/mL DEX had similar blood peak arrival time and peak-to-peak amplitude as lidocaine with 10 μg/mL epinephrine, but it reduced pulse rate. The results of this study suggest that 12.5 μg/mL DEX improves tissue distribution, anesthetic action, and hemodynamic effects of lidocaine in rats. Therefore, 12.5 μg/mL DEX may be a suitable alternative to epinephrine in lidocaine formulations, especially for patients with ischemic heart disease and hypertension.