Local anesthetic activity and acute toxicity ofN-substituted 1,2,3,4-tetrahydro-1- and 2-naphthylamines
ABSTRACT Seven N-substituted 1,2,3,4-tetrahydro-1- and three 2-naphthylamines were prepared and tested for local anesthetic activity in the rabbit corneal reflex test and the mouse sciatic nerve block test. At 0.1 and 1%, three 1-alkylamino compounds had durations of action comparable to that of tetracaine in the rabbit corneal reflex test and were considerably more potent than lidocaine. The other four 1-alkylamino derivatives were inactive or at best minimally active. The durations of action of 1% concentrations of the three 2-alkylamino compounds were equivalent to that of 1% lidocaine in the corneal reflex test. In the mouse sciatic nerve block test, the three active 1-alkylamino compounds were considerably longer acting than either tetracaine or lidocaine. Three 1-alkylamino and the three 2-alkylamino compounds showed toxicity equal to or greater than lidocaine, while two 1-alkylamino and two 2-alkylamino compounds showed toxicity equal to or greater than tetracaine by the intraperitoneal route in mice. N-Heptyl-1,2,3,4-tetrahydro-6-methoxy-1-naphthylamine methanesulfonate was the most promising local anesthetic in these series.
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ABSTRACT: N-Heptyl -1,2,3,4- tetrahydro-6-methoxy-1-naphthylamine methanesulfonate (I) is a potent, long lasting local anesthetic. It was as potent as tetracaine and at least 10 times more potent than lidocaine in the rabbit corneal reflex, guinea pig wheal, and mouse sciatic nerve block tests. The threshold anesthetic concentration (TAC), defined as the concentration required to produce anesthesia lasting 5 min, was calculated from each linear regression line fitted to the log dose-duration data, and these values were used to compare the potencies of the local anesthetics. In the rabbit corneal reflex test, the TAC values were 0.04% for I, 0.04% for tetracaine, and 0.66% for lidocaine. In the guinea pig wheal test, I had a TAC of 0.02%, which was equipotent to tetracaine and 11 times more potent than lidocaine; epinephrine (1:100,000) prolonged the duration of action of all three local anesthetics but had the least effect with I. In the mouse sciatic nerve block test, the TAC values were 0.06% for I, 0.10% for tetracaine, and 0.86% for lidocaine. The acute LD50 values of I in mice were 138 mg/kg sc and 26 mg/kg iv. By either route, I was less toxic than tetracaine and more toxic than lidocaine. Comparison of the LD50 and TAC values in the mouse sciatic nerve block test indicated that I had a greater therapeutic index than either reference standard.Journal of Pharmaceutical Sciences 05/1978; 67(6):882 - 884. DOI:10.1002/jps.2600670648 · 3.01 Impact Factor