In Reply:-I thank Drs. Jones and Taylor for their interest in and comments about my editorial.  They reinforce my point that currently available non-subtype-selective [Greek small letter alpha]2agonists have sedative and hemodynamic effects, and that, at high doses, these hemodynamic effects may cause undesirable side effects. In addition to the cardiovascular and pulmonary effects discussed by Drs. Jones and Taylor, at high doses, these compounds may have deleterious effects on vital organ blood flow in animals and humans. When [Greek small letter alpha]2agonists are used for sedative purposes, their peripheral vasoconstrictive effects seem to cause most of the undesirable side effects, such as the ones described by Drs. Jones and Taylor. Fortunately, it appears that the centrally mediated sedative/sympatholytic effects and the peripherally mediated vasoconstrictive effects are mediated by different [Greek small letter alpha]2-receptorsubtypes. To provide the desired therapeutic effect (sedation) without side effects (vasoconstriction) is precisely why subtype-specific [Greek small letter alpha]2agonists may, in the future, provide the bases for a reversible intravenous anesthetic technique in humans. However, before my enthusiasm for the potential role of the use of [Greek small letter alpha]2agonists in a reversible intravenous anesthetic technique can become reality, new drugs must be developed, undergo rigorous preclinical and clinical testing, and be evaluated by experts in appropriate regulatory agencies, as is common with all new drugs. Meanwhile, continuing research work in this area will lead to better understanding of these compounds, help us to avoid serious side effects, and improve the anesthetic care of animals and humans.
Pekka Talke, M.D.
(Accepted for publication January 13, 1999.)