AL-SAADI D, SNEADER W, WATON N. RELATIONSHIPS BETWEEN LIPOPHILIC CHARACTER AND BIOLOGICAL ACTIVITY OF NEW POTENTIAL LONG-ACTING LOCAL ANESTHETICS. Med J Islam Repub Iran 1996; 10 (1) :53-57
URL:
http://mjiri.iums.ac.ir/article-1-1219-en.html
From the School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Islamic Republic of Iran
Abstract: (4520 Views)
The partition coefficients (P-values) of certain new potential, stereoselective,
reversible, long-acting local anesthetics have been determined in an n-octanol/
phosphate buffer system. These are derivatives of 2-phenoxyethyldialkylamine
hydrochloride, and almost all of them are readily soluble in water. Their aqueous
solutions have shown different absorption maxima, and these have been used
quantitatively to determine the concentration of solute in aqueous phase using the
Beer-Lambert equation and the calibration curve, which has been a straight line
within the test concentrations. The values of P have been calculated as the ratio of
the concentration of solute in the octanol phase divided by the concentration in the
aqueous phase the former value has been obtained from mass balance. The mass
balance is confirmed by obtaining the absorption measurements of the organic
phase. The guinea pig intradermal wheal test has been used to determine the
anesthetic properties of the test agents. They have exhibited better anesthetic
profiles than those of the bupivacaine standard. Moreover, they have displayed no
apparent side-effects neither locally nor systemically. Although there has been no
sharp general correlation between the P-values and duration of action (WT), it is
observed, in many cases, that derivatives with low P-values have shorter WT than
those with high P-values. Therefore, it seems that the duration of action of these
compounds is not influenced only by this property, i.e. P-values, and other factors
such as physicochemical, pharmacokinetic, and pharmacodynamic parameters as
well as non-specific binding characteristics at adjacent tissues are also involved.
Thus, the action of these new compounds is due to the molecule as a whole and not
to any one particular physical or chemical property. Furthermore, these are
reversible and stereoselective agents.