A synopsis on different homologous series of fomocaine derivatives. In vitro interactions with the cytochrome P450 system, toxicity, and local anaesthetic effects in rats--Part 1.

Fomocaine (CAS 56583-43-6) is a basic ether-type local anaesthetic used in dermatological practice for surface anaesthesia. For many years, modifications of the fomocaine molecule have been pursued, e.g. to improve its physicochemical properties and also in view of possible new (systemic) applications, e.g. in the treatment of migraine or as antiarrhythmic. The present paper provides a survey of the investigations undertaken with all the different series of fomocaine derivatives synthesized so far with respect to their in vitro interaction capacity at the cytochrome P450 system, in vivo toxicity (LD50; paresis of the N. ischiadicus) and local anaesthetic effects (conduction anaesthesia at the N. ischiadicus; surface anaesthesia of the cornea) in rats. The main objective of this systematic comparison of the effects of all these substances was to assess possible basic structure-activity relationships.

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.

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.

In vitro interactions with the Cytochrome P450 system, toxicity, and local anaesthetic effects of Fomocaine Alkylmorpholine derivatives in rats.

Fomocaine (CAS 56583-43-8) is a basic ether-type local anaesthetic used in dermatological practice for surface anaesthesia. For many years, modifications of the fomocaine molecule have been pursued, e.g. to improve its affinity to the sodium channel and also in view of possible new (systemic) applications. In the present study fomocaine and eight fomocaine derivatives with an additional alkyl chain in 2- or 3-position of different length (C1 up to C4), or with a branched C3 chain in 3-position, respectively, at the morpholine ring were evaluated in vitro for possible structure-activity relationships with respect to the interactions with cytochrome P450 (CYP) mediated monooxygenase and oxidase functions using rat liver 9000 g supernatants or microsomes. Results were compared to in vivo data from rats on toxicity (LD50), paresis of the N. ischiadicus and surface and conduction anaesthesia (cornea, N. ischiadicus). In general, the influence of the derivatives on the CYP system was less than that of fomocaine, showing a further decline with enlarging chain length. Toxicity of the derivatives was comparable to that of fomocaine and lower only with the compound with a C4 alkyl chain in 2-position. The derivatives caused a stronger surface anaesthesia than fomocaine, exhibiting an additional increase with enlarging chain length. No clear-cut structure-activity relationships were observed with respect to paresis of the N. ischiadicus and to conduction anaesthesia. Especially the derivatives having a C2 or C4 chain in 2- or a C3 chain in 3-position, respectively, may be of interest for further investigations. In comparison to fomocaine they caused a stronger surface anaesthesia combined with a lower interaction capacity with the CYP system.

Single and chronic administration of ciprofibrate or of ciprofibrate-glycinate in male Fischer 344 rats: comparison of the effects on morphological and biochemical parameters in liver and blood.

Fibrates lead to a reduction of serum triglycerides and cholesterol in hyperlipidemic patients. Their therapeutic use, however, can be associated with adverse effects like gastrointestinal disorders, myalgia, myositis and hepatotoxicity. Large doses can even cause hepatocellular carcinoma in rodents. Additionally, interactions with the biotransformation of other compounds at the cytochrome P450 (CYP) system have been observed. Thus, the discovery of new derivatives with less of these side effects is of great interest. In the present study a single (10 mg/kg body weight) or a 4-week (1 or 10 mg/kg body weight daily) oral administration of ciprofibrate or of the newly synthesized ciprofibrate-glycinate was investigated in adult male Fischer 344 rats. Serum lipid concentrations were distinctly decreased after single but only slightly after chronic administration of the two fibrates, whereas liver parameters revealed a slight concentration and time dependent hepatotoxicity. Histologically, a hypertrophy, an eosinophilia, a reduced glycogen content and also an apoptosis of the hepatocytes was observed. Effects were more pronounced after chronic treatment and after application of the higher dosage. All CYP enzymes investigated were induced in a time and concentration dependent manner. Resulting CYP mediated monooxygenase and oxidase activities showed a dependency both on enzyme induction and hepatotoxic effects. With no parameter investigated major differences were seen between ciprofibrate and ciprofibrate-glycinate. Thus, the present investigations revealed no noticeable advantages of ciprofibrate-glycinate over its parent compound ciprofibrate.

Effects and toxicity of new fomocaine derivatives and of 2-hydroxypropyl-beta-cyclodextrin inclusion compounds in rats.

Fomocaine (CAS 56583-43-8) is a local anaesthetic (LA) with good surface anaesthesia and low toxicity, monographed in the German Extra Pharmacopoeia (DAC). In previous experiments it could be shown that both fomocaine and a couple of its derivatives need further pharmaceutical investigations. Therefore, five new C-alkylmorpholine derivatives, (OW 1, OW 3, OW 5, OW 9, and OW 11) and five 2-hydroxypropyl-beta-cyclodextrin inclusion compounds of fomocaine or OE 7000, OE 9000, OL/4, and OL/40, respectively, were compared with fomocaine and/or the respective non-cyclodextrin formulations in rats. Basing on standard methods for testing of LA effects and using two methods to characterising toxicity of LA (paresis of the N. ischiadicus, LD50) it can be concluded that: a) The good surface anaesthesia caused by fomocaine is not surpassed by its alkylmorpholine derivatives OW1-11. Only OW 11 seems to induce longer lasting conductance anaesthesia; the other OW substances (1-9) are in the same range like fomocaine. The toxicity is quite comparable for fomocaine and its OW derivatives. b) Substituted cyclodextrins are often a useful help if the water solubility of compounds is insufficient. The use of these cyclodextrin inclusion compounds resulted in slightly improved LA effects of complexed fomocaine, whereas there were nearly no significant differences between OE 7000 or OE 9000 and their cyclodextrin formulations. The toxicity of the complexed fomocaine was lower compared to fomocaine whereas the toxicity of both OE 7000 and OE 9000 was the same for the original compound and their cyclodextrin formulations. Obviously the paresis of N. ischiadicus is less pronounced after administration of the inclusion compounds. c) The cyclodextrin formulations of the new meta-fomocaines (OL/4 and OL/40) are, compared to the complexed fomocaine, without practically relevant LA effect. But OL/4 complexed is even more toxic than complexed fomocaine. On the basis of the experiments done with altogether five new fomocaine derivatives and five complexed fomocaines it can be summarized that neither the new derivatives nor their inclusion compounds seem to have any therapeutic advantage compared with the known mother substance fomocaine. Only the longer lasting effect of high doses of OW 11 as conductance LA could be of practical relevance.

Fibrates and their newly synthesized glycinate or glycinate-methylester derivatives: comparison of the interactions with liver cytochrome P450 dependent monooxygenase- and oxidase-functions in vitro.

Different fibrates (bezafibrate, ciprofibrate, clofibrate, fenofibrate, gemfibrozil) were investigated in comparison with their newly synthesized glycinate and glycinate-methylester derivatives. Interactions with the cytochrome P450 (CYP) system were studied by assessing binding to CYP and effects on CYP mediated monooxygenase functions in rat liver 9000 g supernatants, as measured by six model reactions for different CYP isoforms (ethoxyresorufin O-deethylation, ethoxycoumarin O-deethylation, pentoxyresorufin O-depentylation, p-nitrophenol-hydroxylation, ethylmorphine N-demethylation, lauric acid 11- or 12-hydroxylation). Possible prooxidant or antioxidant properties were investigated by the stimulated lipid peroxidation, hydrogen peroxide production, and lucigenin and luminol amplified chemiluminescence using rat liver microsomes. Additionally, the influence on luminol amplified rat whole blood chemiluminescence was examined. All substances tested displayed binding to CYP. Effects on the monooxygenase model reactions were in general more distinct with the glycinates than with the parent compounds and most pronounced with the glycinate-methylester derivatives. The slightest effects on all model reactions were seen with clofibrate and its derivatives. On the whole, low antioxidative rather than prooxidative effects were observed. In general and with most model reactions, the antioxidative capacity of the glycinate and glycinate-methylester derivatives slightly exceeded that of the respective parent compounds. Summarizing the results it can be concluded that with respect to possible interactions with the CYP system in vivo and thus with the biotransformation of other concomitantly administered compounds no advantages of the glycinate or glycinate methylester derivatives over their parent fibrates are to be expected. Only the antioxidative capacity of the derivatives was somewhat higher than that of the parent substances, though most probably only of minor therapeutical relevance.

[Conjugation reactions of ciprofibrate with human and laboratory animals]. / Konjugationsreaktionen von Ciprofibrat bei Menschen und Versuchstieren.

An open problem of the lipid lowering agent ciprofibrate (rac-2-[4-(2,2-dichlorocyclopropyl)-phenoxy]-2-methylpropanoic acid, CAS 52214-84-3) is its metabolism concerning the conjugation with amino acids and glucuronic acid. It could be solved by syntheses of the needed reference compounds--unknown up to now--and administration of ciprofibrate to volunteers and rats. Unexpectedly the conjugation compounds with amino acids are stable in vitro and in metabolism. There was no evidence for any conjugation reaction with amino acids by investigating samples of urine and faeces. On the contrary the urine of humans contains 90-97% of beta-O-acylglucuronide, whereas rat urine shows only 10% of the calculated amount.

Local anaesthetic effects and toxicity of seven new diethanolamine and morpholine derivatives of fomocaine. Testing in rats compared with procaine and tetracaine.

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.