Minimum Dosage Technique in the Clinical Comparison of Representative Modern Local Anesthetic Agents

¹ Royal College of Surgeons in Ireland and Royal City of Dublin Hospital, Dublin, Ireland

The clinical efficiency of four of the modern rapid-acting anesthetic agents (lidocaine, mepivacaine, L67, and hostacaine) has been assessed in a series of 1,254 injections. Clinical criteria have been established to allow comparison of a series of parameters, and statistical methods have been applied to evaluate onset and duration times in each case.

The relationship between onset time and duration, on the one hand, and dosage, site, and potency, on the other, has been investigated.

Methods of controlling duration by dosage, agent concentration, and/or epinephrine concentration have been established. The behavior of lidocaine and L67 when their concentrations and/or epinephrine contents are altered was examined, as was the behavior of mepivacaine with and without epinephrine. An attempt was made to explain these phenomena on clinical grounds.

Tables were prepared to show the onset times, extent, and duration of each solution tested for five sites (and in some cases the mandibular block as well) over a range of 0.25-1.0 ml. dosage. From the figures obtained, minimum doses which will produce 98 per cent confidence levels were established for routine dental procedures. In a comparative table, these figures were applied for those solutions which the investigation demonstrated to have practical application, and also for the two solutions capable of producing ultrashort duration where that is required.

Finally, the solutions tested were graded according to clinical potency. Suggestions were put forward as to how the figures obtained and the criteria applied might be adapted in the testing of new agents.