Messung der Leitungs- und Infiltrationsan�sthesie an Ratten mit einer neuen Methode

Until now, no optimal local anaesthetic drug with long lasting effect and low toxicity has been developed. Fomocaine (CAS 17692-39-6), introduced in the German extrapharmacopoela (DAC) in 1979, is a local anaesthetic, which is largely in accordance with these aspects. Now the basic ether fomocaine, its metabolites O/Se 9 (CAS 3006-96-0), O/Se 10 (CAS 31719-76-3), O/Se 11, O/Se 12 (CAS 64264-21-7) and M5 and its chiralic derivatives O/G 3 and O/G 5 were compared with procaine (CAS 59-46-1) and characterised more in detail in rats. The metabolism of fomocaine was investigated earlier with 14C-fomocaine in rats and beagle dogs. Rac-O/G 3 and Rac-O/G 5 could be separated into the enantiomers via the diastereomeric salts. Basing on standard methods for the testing of the local anaesthetic effects (estimation of infiltration and conduction anaesthesia in rat tail, measurement of corneal anaesthesia) and using a couple of tests characterising the side effects and toxicity of local anaesthetic (paresis of the N. ischiadicus, tissue irritation, determination of the approximative i.p. LD50) it can be concluded that: a) The very good surface anaesthesia caused by fomocaine could be stated, but, as expected, concerning conduction anaesthesia, procaine is better qualified for clinical use. b) Fomocaine is much more effective in conduction and surface anaesthesia than its chiralic derivatives O/G 3 and O/G 5. c) Differences between the two enantiomers of the O/G-substances have been found, but these little discrepancies are without practical relevance. In the case of O/G 5, agonistic effects of both enantiomers could be shown. d) Fomocaine undergoes extensive biotransformation with subsequent formation of 14 metabolites. Five of them (O/Se 9-O/Se 12; M5) are N-free and do not show any pharmacological activity. e) Compared to other local anaesthetics, fomocaine is relatively non-toxic (nearly no tissue irritation, high approximative LD50), however, surprisingly the toxicity of the reference substance procaine has been found to be lower after i.p. administration instead of i.v. administration in comparison with fomocaine.

Section: Infiltration Anaesthesiamentioning

confidence: 99%

Section: Conduction Anaesthesiamentioning

confidence: 99%

Local Anaesthetic Effectivity and Toxicity of Fomocaine, Five N-free Fomocaine Metabolites and Two Chiralic Fomocaine Derivatives in Rats Compared with Procaine

Fleck

Kämena

Tschritter

et al. 2011

“…The test substances were administered subcutaneously into the rat's tail near to the right and left nerves of the rat tail [19]. The duration of local anaesthesia was measured in dependence on dose or concentration used.…”

Section: Conduction Anaesthesiamentioning

confidence: 99%

Local Anaesthetic Effects and Toxicity of Seven New Diethanolamine and Morpholine Derivatives of Fomocaine

Fleck

Karge

Loy

et al. 2011

Fomocaine (CAS 56583-43-8) is a local anaesthetic (LA) with long lasting surface effect and low toxicity. Nevertheless, it is not optimal yet. Therefore, 7 newly synthesised derivatives, 4 diethanolamines (OE 6000, OE 7000, OE 8000, OE 9000) and 3 morpholines (OE 500, OE 1000, OE 5000) were compared with procaine-HCl (CAS 51-05-8) and tetracaine-HCl (CAS 136-47-0) in rats. Based on standard methods for the testing of LA effects and using two methods for characterising side effects and toxicity of LA (paresis of the N. ischiadicus, LD50) it can be concluded that: a) The very good surface anaesthesia caused by especially fomocaine and tetracaine could be stated but concerning conduction anaesthesia procaine is better qualified. b) Concerning conduction anaesthesia, diethanolamine derivatives are more potent compared to morpholine derivatives. c) Surface anaesthesia shows a different picture: the effect of fomocaine is in between. d) The paresis of the N. ischiadicus as a first sign of toxic side effects indicated that low effect is combined with short paresis. e) Compared to the LD50 of fomocaine, the toxicity of OE 500 and OE 5000 is only one half. On the basis of the experiments with fomocaine derivatives, distinct structure-activity relationships could be demonstrated for fomocaine derivatives concerning a) LA effects and b) toxicity. Altogether OE 9000 could be a promising candidate for systemic use.

“…The test substances (0.05 ml) were administered into the left hind leg of the rat near to the N. ischiadicus [34]. The duration of the conduction anaesthesia was measured in dependence on the dose (= drug concentration) of the substance used by assessing the time to the reappearance of a retraction of the respective leg after irritation of the foot sole with a blunt needle.…”

Section: Conduction Anaesthesiamentioning

confidence: 99%

Pharmacological and Toxicological Testing of the Enantiomers of two Chiral Fomocaine Alkylmorpholine Derivatives in Comparison to their in vitro Interactions on Drug Metabolism in Rats

Lupp

Wange

Oelschläger

et al. 2011

Between the stereoisomers of amide-type local anaesthetics differences have been noticed with respect to pharmacokinetics and side effects, but not regarding local anaesthetic capacity. Therefore, only S-(-)-ropivacaine has been introduced into clinical practice and with bupivacaine both the racemate and the S-(-)-enantiomer (levobupivacaine) are available by now. Based on this background, the aim of the present study was to evaluate if there are also dissimilarities to be found both in the toxicity and in the effectiveness of the enantiomers of two newly synthesized chiral fomocaine alkylmorpholine derivatives, OW3 and OW13, with an additional C2-chain in 2- or an additional C3-chain in 3-position at the morpholine ring, respectively. For this purpose, in vitro the interaction capacity with cytochrome P450 (CYP)-mediated monooxygenase and oxidase functions was investigated using rat liver 9000 g supernatants or microsomes. In vivo LD50, paresis of the N. ischiadicus and surface and conduction anaesthesia (cornea, N. ischiadicus) were tested in rats. The enantiomers of both OW3 and OW13 caused a concentration dependent inhibition of all CYP-mediated model reactions investigated. With all model reactions the (-)-enantiomer of OW3 was less effective than the (+)-form, whereas the opposite was the case with OW13. Also toxicity was lower with the (-)-enantiomer of OW3 and with the (+)-form of OW13 than with the respective counterparts. With both derivatives no clear-cut dissimilarities were noticed in the local anaesthetic capacity of the enantiomers. None of the four compounds caused paresis. Thus, similar to amide-type local anaesthetics, also with the enantiomers of chiral fomocaine alkylmorpholine derivatives differences in pharmacokinetic properties and toxicity could be demonstrated.