Clinical comparison of pain perception rates between computerized local anesthesia and conventional syringe in pediatric patients.

The purpose of this study was to evaluate pain perception rates in pediatric patients by comparing computerized injection device and traditional injection procedure. In a clinical trial, by using a crossover design, sixty-four patients were randomly assigned to receive, in consecutive sessions, dental anesthetic techniques with either traditional or computerized device. Visual Analogue Scale qualification and heart rate monitoring as physiologic indicator of pain response were used for the evaluation. Results showed that traditional syringe injections were more painful than computerized injection device (p < 0.001). Results suggested that computerized injection device reduces pain perception compared to the traditional syringe during the dental anesthetic management.

Evidence of self-synergism in the antinociceptive effect of tramadol in rats.

Tramadol is an atypical opioid with a complex mechanism of action including the synergistic interaction between the parent drug and an active metabolite. However, the local action of the parent drug is poorly documented. This study was designed to evaluate the site-site interaction of the antinociception produced by tramadol given by two different routes. The effects of individual and fixed-ratio combinations of locally (subcutaneous) and systemically (intraperitoneal) dosed tramadol were evaluated using the formalin test in rats. Isobolographic analysis was employed to identify the synergy produced by combinations. In the second phase of the formalin test, tramadol was active not only by the systemic (ED50 7.15+/-0.46 mg/kg i.p.) but also by the local route (ED50 134.6+/-25.1 microg/paw). The isobolographic analysis evidenced a "self-synergism" in the antinociceptive effect between the two routes of administration since the experimental ED50 (30.8+/-0.1 "dose units") of the combination was significantly lower than the theoretical ED50 (70.9+/-12.6 "dose units"). The mechanism underlying this self-synergism appears to be partially opioid since naloxone reversed the potentiation. The observed site-site interaction in the antinociceptive action of tramadol provides insights for alternatives in the management of pain.