Soft-tissue anesthesia generally lasts longer than pulpal anesthesia, leading to negative consequences such as accidental lip and tongue biting, and difficulty in speaking, smiling, eating and drinking. Now, in a research article published in the latest issue of the Journal of the American Dental Association, it has been reported that phentolamine mesylate (PM) can successfully accelerate the reversal of soft-tissue anesthesia.
Randomized, multicenter, double-blinded, controlled phase III clinical trials were conducted by a team of researchers led by Elliot V Hersh, Professor of Oral Surgery and Pharmacology, and Director of the Division of Pharmacology and Therapeutics, at the University of Pennsylvania School of Dental Medicine, to evaluate the efficiency of PM in decreasing the duration of soft-tissue anesthesia. Patients (n=484) undergoing scaling or restorative procedures were given local anesthetic injections, and after the dental procedure these subjects received either a PM or sham injection (where the needle does not penetrate the soft tissue) at the same site where the local anesthetic was given before the dental procedure. Standardized lip and tongue tapping procedures were done every five minutes for the following five hours, to measure the duration of soft-tissue anesthesia. Functional measures and subject-perceived altered function, appearance, sensation and safety were also evaluated.
The median recovery time in the lower lip, tongue and upper lip were 70, 60 and 50 minutes in the PM group, and 155, 125 and 133 minutes in the sham group, respectively, thus indicating a significant difference (P<0.0001). Significant differences between the two groups were also observed in relation to the recovery from actual functional deficits and subject-perceived altered function, appearance, and sensation. Based on these findings, the researchers concluded that PM was both efficient and safe in shortening the duration of soft-tissue anesthesia and its associated functional deficits.
Tavares M and colleagues conducted a similar study to emphasize the safety and efficiency of PM in pediatric patients, which was published in the same journal. The researcher saw that PM was safe and well-tolerated in children between 4 to 11 years of age, and shortened the post-treatment duration of soft-tissue local anesthesia in children 6 to 11 years of age.
The phase II clinical trails for the drug were done by Mark D Laviola and colleagues (Journal of Dental Research, 2008). A total of 122 participants were included in the double-blind, randomized, multicenter study, who received one or two cartridges of local anesthetic before the dental procedure and 1.8mL of either PM or placebo after the treatment. The median duration of soft-tissue anesthesia in the lip was significantly reduced from 155 to 70 minutes (P<0.0001). The study concluded that PM was efficient and well-tolerated in reversing the soft-tissue local anesthesia.
Local anesthetics, being the most commonly used drugs in dentistry, form an integral part of dental clinical practice. They are the safest and most efficient drugs for the prevention and management of pain in the peri-operative period. The depth and duration of anesthesia is increased by the addition of vasoconstrictors to the anesthetic solution. The prolonged duration of the anesthetic effect can be helpful in extending the dental procedure; but this loss of sensation in the soft tissues of the oral cavity can cause various side effects.
Phentolamine Mesylate is an antihypertensive drug that is indicated in the diagnosis and prevention or control of hypertensive episodes in pheochromocytoma, a neuroendocrine tumor of the adrenal gland medulla. It is also prescribed for the prevention or treatment of dermal necrosis after intravenous administration of norepinephrine. As the current study indicates the safety and efficacy of PM in reducing the duration of soft-tissue anesthesia, it can be now used by dentists to hasten the reversal of anesthesia, thereby reducing the incidence of post-treatment lip and tongue injuries.
References
1. Hersh EV, Moore PA, Papas AS, et al. Reversal of Soft-Tissue Local Anesthesia With Phentolamine Mesylate in Adolescents and Adults. J Am Dent Assoc. 2008 Aug;139(8):1080-1093.
2. Tavares M, Goodson JM, Studen-Pavlovich D, et al. Reversal of soft-tissue local anesthesia with phentolamine mesylate in pediatric patients. J Am Dent Assoc. 2008 Aug;139(8):1095-104.
3. Laviola M, McGavin SK, Freer GA, et al. Randomized study of phentolamine mesylate for reversal of local anesthesia. J Dent Res. 2008 Jul;87(7):635-9.
