Drug Accelerates Recovery After Local Anesthesia

Researchers from the University of Pennsylvania (Philadelphia, USA) and other institutions studied 16 subjects who were enrolled in a phase I trial of phentolamine mesylate. Each subject received four drug treatments: one cartridge of lidocaine and epinephrine followed 30 minutes later by one cartridge of phentolamine submucosaly; one cartridge of lidocaine and epinephrine followed 30 minutes later by one cartridge of phentolamine administered intravenously; four cartridges lidocaine and epinephrine followed 30 minutes later by two cartridges of phentolamine; and four cartridges of lidocaine and epinephrine followed by no phentolamine at all. The pharmacokinetic parameters of the drugs estimated in the study included peak plasma concentration, time to peak plasma concentration, elimination half-life, clearance, and volume of distribution, among others. Additionally, the effects of phentolamine mesylate on the pharmacokinetics of intraoral injections of lidocaine with epinephrine (as used in dental procedures) were also evaluated.

The study results showed that peak plasma concentration occurred earlier following the intravenous (IV) administration of phentolamine (7 minutes) than following submucosal administration (15 minutes) or two cartridges phentolamine after 30 minutes (11 minutes). The phentolamine elimination half-life, clearance, and volume of distribution were similar in all treatments. The researchers suggest that phentolamine may help the body recover feeling faster by counteracting the effect of epinephrine, which delays the body's absorption of lidocaine. The study was published in the Summer 2008 issue of Anesthesia Progress.

"The phentolamine-induced delay of the lidocaine peak plasma concentration likely represents phentolamine's ability to accelerate the systemic absorption of lidocaine from oral tissues into the systemic circulation,” concluded lead author Paul A. Moore, D.M.D., Ph.D., MPH, of the University of Pennsylvania and colleagues.

Phentolamine is a reversible nonselective alpha-adrenergic antagonist, whose primary action is vasodilation. The primary application for phentolamine is for the control of hypertensive emergencies, most notably due to phaeochromocytoma. It is also useful in the treatment of cocaine-induced hypertension. Phentolamine may be stored in crash carts to counteract severe peripheral vasoconstriction secondary to peripherally placed vaospressor infusions, typically of norepinephrine. Phentolamine also has diagnostic and therapeutic roles in reflex sympathetic dystrophy.


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