Most all we know about modern drugs was, perforce, gained from laboratory experiments. So it is with local anesthetics and their side effects. Few humans would wish to volunteer for studies that carry with them the threat of convulsions, however remote it might be. As Dr Moore must know, the efficacy of diazepam as an anticonvulsant in preventing and treating CNS reactions to local anesthetics was established not only by me, but also by Munson, Wagman, Lesse, Feinstein, Wesseling, and other investigators referenced in my textbook.1 Animal species tested were cats, rabbits, rodents, and monkeys. Since all reacted to diazepam in a similar manner, it would seem that extrapolation to man was not an unreasonable step—all the more since not just lidocaine (as Dr Moore intimates) but also procaine, tetracaine, bupivacaine, and etidocaine reactions were reduced in both frequency and intensity by previous administration of diazepam.
de Jong RH. Toxic Effects of Local Anesthetics-Reply. JAMA. 1978;240(5):434. doi:10.1001/jama.1978.03290050024004