US3925469A - Tetiary-alkylamino-lower-acyl-xylidide local anaesthetics - Google Patents

Abstract

Tertiary-alkylamino-lower acyl-xylidides have unusually long lasting local anaesthetic effect or high local anaesthetic activity while also having a satisfactory low level of tissue irritation and a satisfactory low acute toxicity. Combinations of such local anaesthetics with the biotoxins tetrodotoxin or saxitoxin are disclosed. Novel tertiary alkyl secondary amines, and methods for preparing such local anaesthetics and amines are also disclosed.

Description

United States Patent [191 Adams et al.

[ Dec. 9, 1975 TERTIARY-ALKYLAMINO-LOWER-ACYL- XYLIDIDE LOCAL ANAESTHETICS [75] Inventors: Herbert H. F. Adams, Westboro;

Jon C. Anderson, Wyckoff, both of N.J.; Murray R. Blair, Jr., Sudbury, Mass; Robert L. DiRubio, Paxton, Mass; Berti! H. Takman, Worcester, Mass.

[73] Assignee: Astra Pharmaceutical Products, Inc.,

Worcester, Mass.

[22] Filed: June 12, 1973 [21] Appl. No.: 369,146

Related US. Application Data [63] Continuation-impart of Ser. Nos. 230,114, Feb. 28, 1972, abandoned, and Ser. No. 325,378, Jan. 22, 1973, abandoned.

[52] US. Cl. 260/562 B; 424/324 [51] Int. Cl. C07C 103/34 [58] Field of Search 260/562 [56] References Cited FOREIGN PATENTS OR APPLICATIONS 771,151 3/1957 United Kingdom 260/562 307,799 6/1955 Switzerland 260/562 OTHER PUBLICATIONS Epstein et al., J. Amer. Phann. Assoc., Vol. 49, p,

Lofgren et al., Acta Chemica Scand., Vol. 11, p. 1724-1737 (1957).

Primary ExaminerHarry l. Moatz Attorney, Agent, or Firm-Brumbaugh, Graves, Donohue & Raymond [57] ABSTRACT 4 Claims, No Drawings TERTIARY-ALKYLAMINO-LOWER-ACYL- XYLI-DIDE LOCAL ANAESTHETICS This application is a continuation-in-part of our copending applications US. patent application Ser. No. 230,114 filed Feb. 28, 1972, now abandoned, and Ser. No. 325,378 filed Jan. 22, 1973, now'abandoned.

The present invention relates to tertiary-alkylaminolower acyl-xylidide local anaesthetic compounds.

Two acylxylidide local anaesthetic compounds which are commercially available are N-n-butylpipecolyl-2,6- xylidide or bupivacaine sold under the trademark Marcaine having the structural formula CH3 cnzcnzcn zcna H i N NH-"C and diethylaminoaceto-Z,6'xylidide or w-diethylamino- 2,6-dimethyl-acetanilide or lidocaine sold under the trademark Xylocaine having the structural formula However, while bupivacaine or Marcaine is a long lasting local anaesthetic, it has the drawback of being more irritating to tissue than lidocaine and while lidocaine or Xylocaine is not irritating to tissue, it has the drawback of not being a long lasting local anaesthetic.

Other local anaesthetics which are commercially available include a-propylaminopropiono-2-toluidide or prilocaine sold under the trademark Citanest; apyrrolidinoaceto-Z,6-xylidide or pyrrocaine sold under the trademarks Endocaine" and Dynacaine; and N-methylpipecolyl-Z,6-xylidide or mepivacaine sold under the trademark Carbocaine. However, these local anaesthetics are of short action.

It is, therefore, the principal object of the present invention to provide compounds which have an unusually long lasting local anaesthetic effect or high local anaesthetic activity while also having a satisfactory low level of tissue irritation and a satisfactory low acute toxicity.

The local anaesthetic compounds of the present invention are tertiary-alkylamino-acetoxylidides or -propionoxylidides. More specifically, these compounds are as follows:

A. 2-( terL-butylamino )-2 ',6-acetoxylidide B. 2-(tert.-butylamino)-2,6-propionoxylidide C. 2-(N-ethyl-tert.-amylamino)-2',6'-acetoxylidide CHzCH-2CH3 H CH 3 E. 2-(N-n-butyl-te1t. butylamino)-2',6-acet0xylidide F. 2-( N-tert.-amylamino)-2 ',6 '-acetoxylidide These compounds may be synthesized or prepared in accordance with the procedures given in the examples 1 and illustrations set forth hereinafter.

These procedures or processes may be illustrated by the following partial equations:

IA. Preparation of 2-(tert.-butylamino )-2,6'-acetoxylidide Instead of chloro acetyl xylidide, the corresponding bromoor iodocompound may be used. If desired, Nal, KI or a suitably chosen quaternary ammonium iodide may be present during the reaction when the chloroor bromocompound is used.

IB. Preparation of 2-(tert.-butylamino)-2,6-propionoxylidide This compound may be prepared by the procedure described in IA, using the corresponding 2-halo propionoxylidide, instead of the Z-halo acetoxylidide, as the starting material.

II. Preparation of 2-( N-e thyl-tert.-amylamino )-2 ',6 '-acetoxylidide Instead of diethyl sulfate, other ethylating agents may be used, such as ethyl iodide or.ethyl bromide.

The compound may also be made by the reaction described below (IIIA), using CH CI-IO as the starting material instead of CH CH CI-IO.

III. Preparation of 2-(Nn-propyl-tert.-amylamino)-2',6'-acetoxylidide NH-C-CHJ HN CH3 CH CH l... C H 3 CH CH CH H. cu

Instead of the iodo-acetyl xylidide the corresponding chloroor bromocompound may be used as a starting material, in which case a suitable alkali metal or quaternary ammonium iodide will be used to promote the reaction, as in 11 above.

a CH preferably with a suitable acid acceptor. Instead of npropyl iodide, n-propyl bromide may be used.

Preparation of the sec. amines, N-ethyl-tert.-amyl amine, and N-n"-propyl-tert.-amyl amine In addition to the methods described above, these' compounds, which are intermediate compounds in the preparation of the local anaesthetic compounds of the invention, may be made as follows.

NH tert. C H,, suitable ethylating agent tert. C H

suitable propylating agent [c.g. n-C H,1 or nC H Br) NH tert. C H

tert. C H

. e.g., the hydrochlorides, tartrates and citrates. Anaesthetic compounds C and D above provide anaesthesia of significantly longer duration than compounds A and B. Compounds A and B could be used for short procedures in surgery, e.g., such as those requiring infiltration anaesthesia, minor nerve blocks, and certain forms of regional anaesthesia. Compounds C and D could be used in surgery when longer duration of anaesthesia is desired. Because of the possibility of varying the concentration and dose of the agents it is however, possible to obtain satisfactory anaesthesia outside of the range exemplified above with both groups of agents. The compounds A, B, C, D, E and F, moreover when used in combination with biotoxins tetrodotoxin or saxitoxin produce long lasting local anaesthetic effect.

The invention will be further illustrated by the following examples:

EXAMPLE 1 This example illustrates the preparation of 2-(tert.- butylamino)-2',6-acetoxylidide.

To 1 liter of absolute alcohol, 120 g. (0.608 mole) 2-chloro-2,6-acetoxylidide and 272.2 g. (3.108 mole) tert.-butylamine were added. The reaction mixture was heated at C. for 18 hours in an autoclave. After cooling the solvent was evaporated in vacuo. The cream colored residue was dried (vacuum desiccator) and then stirred in benzene for 30 minutes. The undissolved material (tert.-butylammonium chloride).was collected and discarded. The supernatant was evaporated in vacuo leaving a yellowish residue which was collected, dried, and recrystallized twice from petroleum ether (b.p. 60-1 10C.). An 85.9% yield of a white crystalline material, m.p. 8788.5C., was obtained.

Anal. Calcd. for C H- N O: C, 71.75; H, 9.46. Found: C, 71.62; H. 9.43. Ir (KBr disc, base) 3318 (m;

7 sec. amine, 3255 (m; amide, NH-stretch), 1673 (s; amide l), 1592 (w; aromatic), 1495 (s; amide 11), 1385 (w) and 1370 (w) (methyl CH bending), 778 (s; 3 adjacent out of plane aromatic H) cm CH3 l NH-C-CH2--NCCH3 EXAMPLE 2 This example illustrates the preparation of 2-(tert.- amylamino)-2,6-acetoxylidide, and the preparation of 2-( Nethyl-tert.-amylamino )-2 ',6 '-acetoxylidide from 2-( tert.-amylamino )-2 ,6 '-acetoxylidide.

2-(tert.-amylamino )-2',6'acetoxylidide To 400 ml. of anhydrous benzene, 18.9 g. (0.0956 mole) 2- chloro-2,6-acetoxylidide, 20 g. (0.2295 mole) tert. amylamine and l g. of sodium iodide were added. The reaction mixture was heated at 100C. for 36 hours in an autoclave. A precipitate was collected and discarded. The resulting filtrate was stripped of solvent and the yellow oily residue was dissolved in ether, the undissolved material being collected and discarded. After drying (Na SO the ether was stripped off in vacuo leaving a yellow oily liquid which was taken up in dilute hydrochloric acid (final pH 2). The acidic aque ous phase was washed several times with ether, basified to pH 9.5 with concentrated ammonia, and the precipitated base extracted with ether (4X100 ml.). The ether extract was dried (Na S and evaporated in vacuo leaving a yellow oily residue which was distilled in vacuo (b.p. 150C., 0.05 mm.) to give under refrigeration, 16.6 g. ofa white solid, mp. 54-55.5C. (The hydrochloride was also prepared and recrystallized from acetonitrile, mp. 209-21 1C.).

Anal. Calcd. for C I-1 N 01 C, 72.54; H, 9.74; N, 11.28. Found: C, 72.32; H, 9.98; N, 11.34. l.r. (KBr disc, hydrochloride) 3150-3120 (m-s; amide, NH stretch); 2710 (s), 2620 (m), 2580(m), 2440 (m), and 2417 (m-w) (NH stretch); 1665 (s; amide I), 1590 (mw,' aromatic), 1542 (s; amide I1), 1393 and 1375 (s-m; methyl CH bending), 775 (s-m; 3 adjacent out of plane aromatic H) cm.

2-(N-ethyl-tert.-amylamino)-2',6-acetoxylidide To 46.52 g. (0.3017 mole) diethyl sulfate, 10.7 g. (0.0431 mole) 2-(tert.-amylamino)-2 ',6-acetoxylidide was added, and the mixture was heated for 4 hours and 20 minutes at 100C. After cooling the reaction mixture was taken up in hydrochloric acid (final pH 2). The mixture was washed with ether (2X100m1.) and the aqueous solution basified to pH 9 with concentrated ammonia followed by extractions with ether (5X75 ml.). The combined ether extracts were dried (Na SO and the ether removed in vacuo leaving a white solid residue. The residue was recrystallized three times from ethanol/H O. A 37.1% yield of a white crystalline material, m.p. 1ll.5113.5C., was obtained.

Anal. Calcd. for C H N O: C, 73.87; H, 10.21; N, 10.14. Found: C, 73.94; H, 9.94; N, 10.21. IR. (KBr disc, base) 3262 (s; amide, NH stretch), 1655 (s; amide I) 1590 (w; aromatic), 1498 (s; amide II), 1385 and 1375 (w; methyl CH bending), 766 (s; 3 adjacent out of plane aromatic H) cm.

CH3 CH EXAMPLE 3 This example illustrates the preparation of 2-(N-npropyl-tert.-amylamino)-2,6-acetoxylidide from N-npropyl-tert.-amylamine.

N-n-propyl-tert.-amylamine A suspension of 1.0 g.

of 10% palladium on charcoal in ml. absolute alcohol was shaken with hydrogen until more hydrogen was absorbed. To the catalyst mixture, 30 g. (0.3442 mole) tert.-amylamine was added followed by a solution of 18 g. (0.3098 mole) propionaldehyde in 50 ml. of absolute alcohol. All of the above ingredients were cooled in an ice bath before combining. After warming to room temperature, the reaction mixture was shaken with hydrogen at an initial pressure of 59 psi for 10 hours, by which time the theoretical amount of hydrogen was absorbed. The catalyst was separated by filtration, washed with ethanol, and 40 ml. of concentrated hydrochloric acid was added to the combined filtrate. The solution was brought to dryness by evaporation in vacuo. The dried product was dissolved in 250 ml. distilled water and g. of 50% sodium hydroxide was added slowly with cooling to liberate the amine. The mixture was extracted with ether (3X200 ml.) and the combined ether extracts were dried over anhydrous sodium sulphate. The dried extract was distilled through a 300 mm. column packed with /811'1Cl1 1D glass helices yielding 26.7 g. 66.7%) on N-n-propyl-tert.-amylamine, b.p. l36.5-137.5C. (atmospheric pressure), n 1.4106.

Anal. Calcd. for C H N: C, 74.34; H, 14.82; N, 10.84. Found: C, 74.76; H, 15.16; N, 10.96.

HN CH1,

9 2-(N-n-propyl-tert.-amylamino)-2',6' -acetoxylidide To 150 ml. benzene, g. (0.0346 mole) 2-iodo-2',- 6' acetoxylidide and 11.18 g. (0.0865 mole) N-n-propyl-tert.-amylamine were added. The reaction mixture was refluxed for 29 hours. After cooling the reaction mixture was stripped of benzene and unreacted amine in vacuo. The resulting semisolid material was treated with anhydrous ether. The undissolved material was filtered off and discarded and the ether was evaporated in vacuo. The yellow, waxy material was recrystallized twice from ethanol/water and twice from acetone/water. A 49.4% yield of white crystalline material, m.p. 96.5-97.5C., was obtained.

Anal. Calcd. forC H N oi, C, 74,43; H, 10.41; N, 9.65. Found: C, 74.4; H, 10.35; N, 9.59. l.r. (KBr disc, base) 3240 (m; amide NH stretch), 1665 (s; amide l), 1495 (s; amide 11), 1385 and 1370 (w, methyl CH bending), 766 (s; 3 adjacent out of plane aromatic H) cm. A hydrochloride was prepared from the base. It was obtained as a stable monohydrate melting at l81.2l82.8C.

Anal. Calcd. for C H ,C1N O H 0: H 0, 5.22. Found: (Karl Fischer) H O, 5.21.

EXAMPLE 4 This example illustrates the preparation of 2-tert.- butylamino)-2,6-propionoxylidide.

To 300 ml. of absolute alcohol, 38.42 g. (0.15 mole) of 2-bromo-2,6"propionoxylidide and 54.85 g. (0.75 mole) of tertiary butylamine were added. The reaction mixture was heated at 100C. for 18 hours in an autoclave. After cooling, the alcohol and unreacted amine were removed by distillation in vacuo. The residue was dissolved in ether and concentrated NH OH was added. Undissolved material (tertiarybutylammonium bromide) was collected and discarded. The two phase supernatant was separated and the basic aqueous phase discarded. The ether phase was dried over anhydrous Na SO and subsequently removed in vacuo. The cream colored residue was stirred in benzene for 30 minutes. Undissolved material (tertiarybutylammonium bromide) was collected and discarded. Evapo ration of the benzene in vacuo gave a cream colored residue which collected, dried and recrystallized three times from petroleum ether (b.p. 601l0C.). A

54.1% yield of white crystalline material, m.p.

124.5126C., was obtained.

Anal. Calcd. for: C H N O: Calcd.: C, 72.54; H, 9.74; N, 11.28. Found: C, 72.62; H, 9.83; N, 11.34.

0 H ca, NH cu 1L C/CH CH3 CH3 EXAMPLE 5 This example illustrates the preparation of N-npropyl-tert.-amylamine.

A mixture of 2 moles of tert. amylamine and 1 mole of l-bromo-propane is refluxed for 6 hours. The reaction mixture is cooled and kept at +4C. for 1 hour. After filtering, the filtrate is fractionated by column distillation and the colorless, clear fraction boiling between 136l38C. is collected.

EXAMPLE 6 tracted twice with ether. The ether extract is discarded and the aqueous phase is made alkaline by the addition of concentrated ammonia to a Ph of 9-10 whereafter it is extracted several times with ether. This ether extract is dried (K CO and, after filtering, the ether is removed in vacuo. The residue is recrystallized from ethanol/water.

EXAMPLE 7 1n a manner similar to the preparation of 2-(tert.- amylamino)-2,6'-acetoxylidide of Example 2, 2- chloro-2,6'-acetoxylidide is reacted with N-n-propyltert.-amylamine in the presence of sodium iodide to fonn Z-(N-n-propyl-tert. amylamino)-2,6'-acetoxylidide. The resulting reaction mixture is worked up as described in Example 3 for this compound.

EXAMPLE 8 This example illustrates the preparation of 2-[N-(nbutyl)-tert. -butylaminol]-2,6'-acetoxylidide.

A mixture of 600 g. 2-iodo-2',6-acetoxylidide, 643

-g. N-(n-butyl)-tert.-butylamine, and 4.5 liter of benzene were heated to reflux in a flask equipped with a machanical stirrer and a reflux condenser for l5-l6 hours. The compound N-(n-butyl)-tert.-butylamine is described by J. N. Tilley and A. A. R. Sayigh in J. Org. Chem. 28, 2076 (1963). It is prepared analogously to N-propy'terL-amylamine of Example 3 from nbutyraldehyde and tert.-butylamine. After cooling the precipitate of N-(n-butyl)-tert.-butylammonium iodide was filtered off (dry weight 482 g.). The filtrate was extracted with 4 M hydrochloric acid. (The acid extract can be filtered and washed with ether at this point). The acid extract was made alkaline with 7 M sodium hydroxide. The precipitate was taken up in methylene chloride and the alkaline solution was extracted with the same solvent. The methylene chloride solutions (combined) were dried (Na SO after filtered, and evaporated. The residue was recrystallized from a mixture of acetone and water (7-8: l) and a yield of 414 g. was obtained, m.p. l40-l40.5.

Calcd. for C H N O: C, 74.4; H, 10.4; N, 9.65. Found: C, 74.6; H, 10.5; N, 9.49.

B is 2-(tert.-butylamino)-2,6-propionoxylidide.

C is 2( N-ethyl-tert.-amylamino)-2,6-acetoxylidide.

D is 2-(N-n-propyl-tert.-amylamino)-2,6-acetoxylidide.

E is 2-(N-n-butyl-tert.-butylamino)-2,6'-acetoxylide.

F is 2-(N-tert.-amylamino)-2,6'-acetoxylidide.

X is the prior art compound N-n-butylpipecolyl-2,6-

xylidide, i.e., bupivacaine or Marcaine.

Y is the prior art compound diethylaminoaceto-2,6-

xylide, i.e., lidocaine or Xylocaine.

Tables I, II and III contain comparative data on the 3 CHZCHzCHzCHa duration of several of these local anaesthetic compounds, Table IV contains comparative data on the ef- NHCOCH N 15 feet on the action potential of the isolated frog sciatic nerve preparatron of some of these local anaesthetrc C (CHM compounds while Table V contains comparative data on the acute toxrcrty of several of the local anaesthetrc CH 70 compounds. Table VI contains the data from tests on 3 peridural anaesthesia in the dog for compound D. Table VII contains data from tests run on compound B on rat sciatic nerve blocks, guinea pig wheals, irritation on the rabbit back, and acute toxicity in mice. The COmPOUnd y y Irritation indices -reported in Table VI are deter- 2',6'-acetoxylidide may also be prepared by the proce- 25 i d i h f ll i manner; dure described in Example 6 from Wheals are made on the shaved backs of albino rabbUty1amiI10)-2',6l"acetoxylldide and y bromidebits by intraderrnal injection of aqueous solutions of the It y also be P p y the Procedure described agents. Twenty-four hours later each wheal is graded in Example 7 from Z'ChIOYO-Z',6"aCet0Xylidide and for: presence and severity of erythema, presence and n-butyl-tert.-butylamine. 3O severity of edema, and presence or absence of necrotic In the tables presented below the following code destissue in the wheal. The grading is done on an arbitrary ignations have been used: numerical scale, and a mean irritation index is calcu- A is 2- tert.butylamin0)-2.6'-acetoxylidide. lated for all wheals at a given concentration.

TABLE I Rat Sciatic Nerve Blocks* Duration in Minutes Standard Deviation 7c Conc. as base A C D X Y 0.125 88:11 115:16 124150 121132 0.25 173120 159130 157130 175:16 102115 0.5 184:3? l60:l0 217125*** 212134 123110 1.0 250 1 32 20s 1 35 8-27 days 213 102 1 39 2.0 270 1 28 l-8 days 13-30 days I85 1 23 All solutions contained l:lO0.000 epinephrine.

*Test method given in Truunt. A.P.: Arch Int. Pharrnacodyn. l l5: 483-497 (1958). which is incorporated by reference herein.

"Mean of 3; 7 blocked between 5 and 22 hours.

*Mean of 3'. 2 blocked lO-l3 days.

TABLE II Guinea Pig lntradermal Wheals* Duration in Minutes Standard Deviation All solutions contained l:l00,000 epinephrine.

Test method given in Bulhr'mg. Eyand Wajda. It: J, Pharmacol. Exp. Therupr 85: 78-84 1 W451 which is incorporated by reference herein.

TABLE I11 TABLE VI! Peridural Anaesthesia in the Cat* Duration of Block of Support of Weight in Minutes i Standard Deviation Compound B: 2-(Tert. butylamino)-2',6'propionoxylidide Local Anaesthetic and Acute Toxicity Testing graionc. A C X Y 5 V Rat Seiatic* I Concentration Duration Minutes Frequency 0.5 136 t 30 1.0 54 i 9 220 i 64 296 i 77** 32E; 2.0 104:29 298-:56*** 88:10 1 12415 10/10 All solutions contained l:l00,000 epinephrine. 1 144 I 9 10/10 Test method given in Duce, B.R.. Zelechowski. 14.. Camougis, G. and Smith. 20% 164 i 10 0,10 E.R.: Brit. J. Anaesth. 411579-58 (1969). which is incorporated by reference Guinea Pig wheal* herein. Concentration it: Duration Minutes Frequency Toxic effects observed at this concentration. 7 *Mean of 3 animals; 1 blocked 7 hours. 25% 139 i 24 12/12 .5% 160:43 12/12 TABLE IV 15 1.0% 184136 12/12 In vitro Studies on Frog Sciatic Nerve Block C t Back Greatest Depth of Average time for 80% once m a "lumen ndex Concn. Block of action recovery of action 5% 0 Compound mM potential) potential (min) 3 1 0 2.0% .5 C 77 29 2 2 22 22 20 Y 20 46 14 61 (45-78 mg/kg LP.

"Solutions contained l:l00.000 epinephrine T V "Depression. ataxia, loss of fighting reflex in some animals at this concentration.

Acute Toxicity in Female Mice Compound LB and 95% Fieller Confidence Limits: mg/kg as Base 25 lntraperitoneal (1.1.) Intravenous Subcutaneous A 119(92-136) 35.4(312-41) l4l(l2l-l62) C 81(62-132) 7.4(6.5-8.4) D 39(1062) 6.8(6.07.8) 109(78-143) X 40(28-56) 6.4(5.5-7.3) (38-54) Y 105(93-132) 19.5( 18-24) 211(183-256) 30 Solutions did not contain epinephrine.

TABLE VIII Formulations for 0.25%, 0.50%, 1.00%, 1.50%. and 2.00% Compound D:HC1 solutions for injection containing l:200.000 epinephrine are given below.

' mg./ml.

Compound DZHCl H O 2.64 5.28 10.55 15.82 21.10 Sodium chloride, USP XVIII 8.60 8.20 7.30 6.40 5.60 Epinephrine, USP XVlll 0.005 0.005 0.005 0.005 0.005 Sodium metabisulfite 0.50 0.50 0.50 0.50 0.50 Water for injection, USP XVIII qs ad 1.0 m1.

Indicates percent anhydrous Compound DzHCl TABLE VI In Table IX data are presented showing the duration Pcridural Anaesthesia in the of blocl age ofi' rat sciatic nerves by compound E in con- Compound D centrations of -0.25l .0% w/v tested by the same Cmcenmm vlume (mm) method as used for the workrepotted in Table I. Fre- (ml) Digital Scrotal Pain Pain quencies and durations were good.

Epinephrine l:l00.()()(l used in all solutions. The values l'or the durations are mean values and the ranges are given in parenthe- Method: Mature male beagles are surgically prepared by implantation of a cunnula into a lumbar vertebra so that drug solutions may be administered into the pcridural space. After administration of local anaesthetic solutions. the animals are examined at intervals for duration of loss of pain in the scrotal area and in the digits of the hind lim Response to and awareness of pain stimuli in scrotal areas is a test for anaesthetic block in spinal roots L3-4 and 51-2-3. These roots are the furthest removed from the point of injection (L6) and. therefore. least likely to be tllTCCILtl hy the anaesthetic. Return of response to pain in the scrotum is often the first sign of recovery and indicates recession ofunacsthcsia to at least 1.4 antcriorly and S2 posteriorly.

Test method: See Table I.

Compound E was also tested for toxicity in mice, rats, and guinea pigs. In mice the'I.P. toxicity (LD was 284 (21853l) mg/kg. In the rat, subcutaneous toxicity was 1068 (813-4507) mg/kg. In guinea pigs tested subcutaneously all animals survived 646 mg/kg.

The compounds of the present invention are also useful in combination with the known biotoxins, tetrodotoxin, desoxytetrodotoxin and Saxitoxin as described and claimed in the copending application of Adams and Takman, Ser. No. 369,202 filed June 12, 1973 which is a continuation-in-part of application Ser. No. 206,181 filed Dec. 8, 1971 and in the copending application of Adams and Takman Ser. No. 369,147 filed June 12, 1973 which is a continuation-in-part of Ser. No. 206,182 filed Dec. 8, 1971, the disclosures of which are incorporated herein by reference.

The following Table X gives the results of tests on the anaesthetic effect of various compositions of the aminoacylxylidides disclosed and claimed herein with the biotoxins, tetrodotoxin or saxitoxin. It will be noted that the herein claim aminoaeylxylidides have the distinct advantage, in combination with such biotoxins, of providing anaesthetics having unusually long nerveblocking effect.

TABLE X (min. quency 126 i 12 157 1: 18 295** 420 min.*** 24 hrs. 420 min. 24 hrs. 128 i 13 133 i 316 i 10** 420 min. 24 hrs. 420 min. 24 hrs. 97 i 4 TTX TTX TTX 1.0 3

TTX 1 TTX, 0.25

TTX 0.5 l

STX

STX 420 min.

24 hrs. 420 min. 24 hrs.

STX 1.0 2

Footnotes for Table X *For test method. see Table 1. One animal blocked 420 min. 5 *The notation 420 min. 24 hrs. means that the animals recovered during a period when they were not observed.

The test solution of compounds A and B contained epinephrine in a conec ntration 11100000.

The effect of compositions of compounds D and E, respectively, with tetrodotoxin (TTX) was also evaluated by tests on frog sciatic nerves. The pH of the tests was 5.6 and the method used is described below.

Compound D and TTX alone gave 24 and 29 reduction, respectively, in the action potential, whereas the combination of the two in the same concentrations reduced such potential by 94%. In the case of compound E, the reduction in the potential produced by the combination was 94%, as compared with 22 and 15%, respectively, for compounds E and TTX alone. There is, therefore, a decidedadvantage in the combination of the two drugs as compared with the individual compounds. (See Table X1).

TABLE x1 Effect of the presence of compounds D and E on Tetrodotoxin (TTX) blocks of isolated intact frog sciatic nerve at pH 5.6.

*The numbers in parenthesis indicate the range observed in the experiments **An occasional high value is sometimes observed. The logical explanation for this is some minute injury done to the nerve sheath during dissection. It takes about 50 times the concentration of TTX necessary to block a desheathed nerve in order to obtain the same degree of block of an intact (sheathed) nerve.

Following the procedure described above in Table VI, tests were made on the nerve blocking effect of compounds D and E, respectively, combined with the biotoxin, saxitoxin, in peridural anaesthesia in the dog. The data obtained are presented below in Table XII. It will be noted that compound D alone gave a duration of block of digital pain and scrotal pain of 289 minutes and 218 minutes, respectively, whereas in combination with saxitoxin, duration of block was l-2 days for digital pain and more than 8 hrs. for scrotal pain. Compound E in a 2% solution produced a duration of block of l to 2 days for digital pain and greater than 7% hrs. for scrotal pain. All animals recovered completely.

TABLE XII Peridural Anaesthesia in dog with compounds D and E added to Saxitoxin (STX) solutions. STX 4 ug/ml. Volume 5 m1.

Drug Duration of block of Digital Scrotal (concn.) Pain Pain D 1% l-2 days 480 min.

24 hrs. E 2% l-2 days 420 min.

24 hrs.

Epinephrine l:l00,000 used in all solutions.

Method: See Table VI.

Note:

A volume of 10 m1. 1% solution of Compound D gave durations of block of digital pain and scrotal pain of 289 min. and 218 minutes respectively (Table VI).

Compound D was also tested alone and in combination with Saxitoxin (STX) in spinal anaesthesia in sheep. The results and the procedure followed are described in Table XIII below. It is significant that, particularly in the case of digital pain, the addition of compound D to Saxitoxin increased the duration of block from about 69 to about 267, an increase of about 3% fold.

The solutions contained 7.57: dextrose (pH 4.0). One ml. was administered in each experiment. The sheep (23-29 kg.) were restrained in the horizontal position during the injection and then immediately tilted so that the slope of the spine was positioned ten degrees to the horizontal plane (caudal inferior). The administration was performed between I.6-S1 and was made with 22 gauge three inch disposable needles using the socalled lateral rather than the midline approach,

Note: I

Compound D alone in a concentration 01' 171, i.e.. four times the concentration used in the experiments summarized above, provided a duration of block of digital pain that lasted for 45 61) min. with an onset time of 5-10 minutes.

Compounds D and E were tested for their effect on the brain and the spinal cord in the peridural cat following the procedure described in Table III above. Compound D was tested in 1% concentration and compound E in 2% concentration. Following the tests the brain and the entire spinal cord were examined and no pathological change attributable to the drugs was found.

The results reported in the preceding tables on the in vitro studies on frog sciatic nerve were obtained by use of the following method, essentially as described by A. P. Truant, Arch. Int. Pharmacodyn. 115: 483497 (1958):

Sciatic nerve trunks of Rana pipiens are prepared by dissecting the nerve from its roots in the spinal cord to the ankle and placing it on silver silver chloride electrodes so that stimulation and recording can be performed during the course of application of the test compounds and during the recovery period. The bathing solution is Tasaki Ringers, and for each block and recovery the pI-Is of the drug solution and the recovery solution were identical.

The irritation liability of the compounds was determined according to a test procedure given in A. P. Truant, Arch. Int. Pharmacodyn. l 15: 483-497 (1958). At the concentrations that are of clinical significance, compounds C and D were not more irritating than bupivacaine at 0.5% concentration.

The test method employed for the acute toxicity studies reported in Table V was as follows:

Sexually mature female animals are used.

Animals are divided into groups of and dosed with drug solution or vehicle. After being dosed, animals are observed at intervals for several hours for overt effects and fatalities. Survivors are housed as groups according to dose level and checked once daily for the duration of the study in order to determine whether or not delayed fatalities occur.

LD s and 95% Fieller confidence limits (or 95% approximate limits) are calculated by the Minimum Lo git Chi Square Method of Berkson, J. Am. Stat. Assoc. 48: 565 (1953).

The tertiary-amylamino-acetoxylidide compounds of the invention (compounds C and D) have unusual, long-lasting local anaesthetic effect and high local an- 18 aesthetic activity, satisfactory low level of tissue irritation and satisfactory low acute toxicity compared with bupivacaine (compound X). The tertiary-butylaminoacetoxylidide compound of the invention (compound A) has an unusually longlasting local anaesthetic effect and an unusually low intravenous toxicity compared to its structural isomer lidocaine (compound Y). Its tissue irritation liability is also quite satisfactory.

Generally, the compounds of the invention will be used in 0.252% water solution with or without addition of a vasoconstrictor in infiltration anaesthesia, peridural and subarachnoid anaesthesia. Their use is, however, not restricted to this concentration range and the ,dose and concentration used must be determined in @each case with consideration given to such factors as the age and body weight of the patient, as well as to the route of administration, and the clinical anaesthetic requirements. The compounds of the invention can also be applied topically to mucous membranes and damaged, e.g., abraided, skin in the form of solutions, ointments, jellies, or aerosols. Examples of suitable pharmaceutical compositions which may be used as local anaesthetics are given in Table VIII, using compound D as the active ingredient. Similar compositions, using. compounds A, B, C, E or F as the active ingredient may be formulated in a manner known in the art, possibly adjusting the NaCl content to obtain isotonicity.

We claim:

1. A local anesthetic compound selected from the group consisting of 2-(N-ethyl-tert.-amylamino)-2,6- acetoxylidide and a pharmaceutically acceptable salt thereof.

2. A local anesthetic compound selected from the group consisting of 2-(N-n-propyl-tert.-amylamino)- 2' ,6-acetoxylidide and a pharmaceutically acceptable salt thereof. 1

3. A local anesthetic compound selected from the group consisting of Z-(N-n-butyl-tert.-butylamino)-2,- 6-acetoxylidide and a pharmaceutically acceptable salt thereof.

4. A local anesthetic compound selected from the group consisting of 2-(N-tert.-amylamino)-2',6- acetoxylidide and a pharmaceutically acceptable salt thereof.

UNITED STATES PATENT AND TRADEMARK OFFICE @ER'HHCATE OF CURRECTIQN PATENT NO. 3,925,469 DATED December 9, 1975 INV ENTOR(S) Herbert J. F. Adams et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: 7

First page of patent, after the caption "Inventors: "Herbert H, F. Adams, Westboro; Jon C. Anderson, Wyckoff, both of N.J. should read Herbert J. F. Adams, Westboro, Mass. Jon C. Anderson, Wyckoff, N.J. Col. 5, line 48, il tsert B. Col. 7 line 4, "cmshould read cm Col. 8, line 36, "until more" should read until no more Col. 9, line 12, before "white" insert a line 65, before "white" insert a Col. 10, line 54, "butylaminol should read butylamino line 62, "N-propy-tert.amylamine" should read N-propyltert.amylamine Col. 11,

line 33, 2-tert.butylamino) 2' ,6 acetoxylidide" should read 2- (tert.butylamino) 2' ,6'acetoxylidide Col. 12, line 18, "the local" should read these local Col. 13, line 12, "579-58" should read 579-587. Col. 14, line 5 of Table VIII, the caption "0.25%" should read 0.25%* Col, 15, line 10, "369,202" should read 369,302

line 21, "claim" should read claimed Signed and Sealed this twenty-fifth Day Of May 1976 {SEAL} Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner uj'Parenls and Trademarks

Claims (4)

1. A LOCAL ANESTHETIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF 2-(N-ETHYL-TERT.-AMYLAMINO)-2''-,6'',ACETOXYLIDIDE AND A PHARMACEUTICALLY ACCEPTABLE SALT THEREOF.

2. A local anesthetic compound selected from the group consisting of 2-(N-n-propyl-tert.-amylamino)-2'' ,6''-acetoxylidide and a pharmaceutically acceptable salt thereof.

3. A local anesthetic compound selected from the group consisting of 2-(N-n-butyl-tert.-butylamino)-2'' ,6''-acetoxylidide and a pharmaceutically acceptable salt thereOf.

4. A local anesthetic compound selected from the group consisting of 2-(N-tert.-amylamino)-2'' ,6''-acetoxylidide and a pharmaceutically acceptable salt thereof.