Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.59 no.1 Campinas Jan./Feb. 2009
LETTERS TO THE EDITOR
histologic spinal cord and neurologic changes in guinea pigs after subarachnoid
block with large volumes of racemic bupivacaine, 50% enantiomeric excess bupivacaine
(S75-R25), and levobupivacaine
(Rev Bras Anestesiol, 2008;58:234-245)
Q. S. P. (quantum satis para...).
To the Editor,
The enantiomeric mixture of bupivacaine (S75-R25) has completed its first decade since it was created. This was possible due to the formula in which the pharmacotechnical principle "quantum satis para" (Q. S. P.) ensured its survival due to the efficacy/safety binomium.
On October 30, 1988, the deadline for papers for the ASRA Annual Meeting, Philadelphia, USA, this new local anesthetic guaranteed its birth certificate 1; its baptism came soon after 2; and it recently received its confirmation with this basic research 3.
In this trajectory, it is possible to confirm that this compound was well-born, having received all sacraments before reaching adolescence. It represents the triumph of basic research, which created a rational combination based on stereoisomeric evidence.
Vasconcelos Filho et al. circumscribed his work on the main finality by which local anesthetics exist: nerve block, more precisely, the larger structure, the spinal cord. The partnership among departments enriched Brazilian basic research through the collaboration of the Capelozzi Professors, who allowed our investigative capacity to be known abroad through the respectable journal Anesthesia & Analgesia several years ago3. And very few among us had this honor.
On the three rehearsed presentations of bupivacaine, of the pipecoloxylidides family (the racemic, the homochiral, and the enantiomeric mixture) it was possible to demonstrate, qualitatively and quantitatively, the toxicological differences due to the spatial disposition of its isomers (S(-) versus R(+) bupivacaine).
Stereoisomerism provides us the script: isomers are markedly different... One only has to balance them "juste mesure", i.e., "quantum satis para" without causing tissue damage, which happened through the non-equimolar handling of racemic bupivacaine in the S75-R25 formulation, which did not differ statistically from the homochiral compound (levobupivacaine) 1,2,3.
To collaborate with this project, structured under such a reliable method, I suggest the comparison with another branch of this family, the compound (p) ropivacaine intrinsically vasoconstrictor susceptible to accidental intrathecal administration when the epidural technique is used.
Therefore, we will wait for the impact of the vasoconstriction of ropivacaine on spinal structures, maybe the reason for its contraindication in the subarachnoid technique.
Maria P.B. Simonetti, TSA
01. Simonetti MPBS, Ferreira FM Does the D-isomer of bupivacaine contribute to improvement of efficacy in neural block. Reg Anesth, 1999;24(Supp ASRA):43. [ Links ]
02. Trachez MM, Zapata-Sudo G, Moreira OR et al. Motor nerve blockade potency and toxicity of non-racemic bupivacaine in rats. Acta Anaesthesiol Scand, 2005;49:66-71. [ Links ]
03. Vasconcelos Filho PO, Posso IP, Capelozzi M et al. Comparação das alterações histológicas da medula espinal e neurológicas de cobaias após anestesia subaracnóidea com grandes volumes de bupivacaína racêmica, de mistura com excesso enantiomérico de 50% de bupivacaína (S75-R25) e de levobupivacaína. Rev Bras Anestesiol, 2008;58:234-245. [ Links ]