diverse studies have demonstrated that the related problems to medicines (prms) originate of errors in the prescription and the adverse reactions that repel in negative effects on the health. objective: to analyze the use of the local anesthetic (al) actually odontological and to identify problems related to its use. materials and methods: study of observacional, crosssectional type. they were analyzed: clinical effectiveness of the a and the adverse reactions to medicines (ram). data were collected about: time of injection, time of latency and scale of the pain actually clinical odontologica on patients. results: in the times of injection there were no differences; yes there was between dixcaína and the rest in time of latency. in the pain scale, there was no pain for dixcaína and there was moderate pain for carticaína. conclusions: the valuation and pursuit of the problems related to the medicine use mean a direct benefit for the society.