Therapeutically Active, Substituted Piperidines and Pyrrolidines Therapeutic Compositions Thereof and Methods of Use Thereof

The present invention relates to new chemical compounds, methods of manufacturing them, pharmaceutical preparations containing these substances and methods of treatment using these compounds in order to produce local anaesthetic, topical anaesthetic and anti-arrhythmic effects in mammals.

The membrane stabilizing substances lidocaine and mepivacaine have been clinically used both as local anaesthetics and as anti-arrhythmic agents for the heart. The usefulness of lidocaine and mepivacaine is, however, limited by the toxic properties of the substances, in particular by their general toxicity and their tissue toxicity when the substances are used as local anaesthetics, and their general toxicity when the substances are used as anti-arrhythmic agents for the heart.

The present invention relates to new substances which, in experiments performed on animals, have been found to have a better therapeutic index, that is a therapeutic margin, than lidocaine and mepivacaine.

The present invention provides compounds of formula I below in the form of racemates or their optically active isomers: ##STR2## in which R is a straight or branched alkyl residue containing 2 to 4 carbons and a terminal hydroxy group, R.sub.1 is selected from the group consisting of methyl and methoxy, R.sub.2 is selected from the group consisting of methyl and ethyl, R.sub.3 is selected from the group consisting of hydrogen and methyl and m and n are a pair of integers such that m=0 or 1 and n=3-m or m=0, 1 or 2 and n=4-m.

The compounds may alternatively be in the form of pharmaceutically acceptable salts.

In formula I, R may be, for example selected from the group consisting of 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, 2-hydroxy-1-methylethyl, 3-hydroxy-1-methylpropyl, 3-hydroxyl-2-methylpropyl, quaternary 2-hydroxyethyl-N-methyl, quaternary 3-hydroxy-1-methylproply-N-methyl, quaternary 3-hydroxyproply-N-methyl, quaternary 2-hydroxyethyl-N-ethyl and quaternary 3-hydroxyproply-N-ethyl.

Examples of compounds of the present invention are as follows: ##STR3##

Compounds of formula I can, for example be manufactured in accordance with the following methods of preparation:

A pyridine or pyrrole carboxylic acid anilide (a) is hydrogenated to the corresponding piperidine or pyrrolidine carboxylic acid anilide (b) which is thereafter hydroxy-alkylated to form a compound in accordance with formula I. R.sub.1, R.sub.2 and R.sub.3 in (a) and (b) are as defined in Formula I. ##STR4## The formula ##STR5## is used herein to designate that either the corresponding ##STR6## compound can be used.

The formula ##STR7## is used herein to designate that either the corresponding pyridine or pyrrole compound can be used. ##STR8##

Compounds of formula (a) can alternatively be produced by reacting a pyridine or pyrrole carboxylic acid chloride (i) with an aromatic amide (j) ##STR9## or by reacting a pyridine or pyrrole carboxylic acid ester (e) with a metal organic derivative of an aromatic amine (f) ##STR10## wherein X=halogen and R.sub.1, R.sub.2 and R.sub.3 in (d) and (f) are defined as in formula I.

The compounds of formula I can also be produced by reacting a piperidine or pyrrolidine carboxylic acid (g) with an aromatic amine (d) or the corresponding isocyanate (h) to form a compound of type (b) identified above which can then be hydroxyalkylated to form a substance in accordance with formula I. ##STR11##

An acid of type (g) may first be converted to a more reactive derivative, such as an acid chloride (i), an acid anhydride or an ester (e), whereupon the derivative thus produced is caused to react with the aromatic amine (d) or the aromatic isocyanate (h) after which the compound of type (b) obtained is converted to a compound in accordance with formula I by means of hydroxy-alkylation.

Other methods of producing compounds of formula I, or intermediate products which could be converted to compounds of formula I, apart from those illustrated in Methods A-C above, may also be used. Alternative methods of preparation are described for example in Swedish Pat. Nos. 161236, 161237, 161519, 164062, 164063, 164674, 191321, 191322 and 192045 which are incorporated herein by reference.

In order to produce the compounds of the present invention by the methods described in the Swedish patent specifications, the N-alkylation process must be modified so that the alkylation agent contains at least one reactive hydroxylalkyl group or group which can be transformed in a simple operation to a hydroxyalkyl group, such as by means of hydrolysis. The most suitable alkylation agents are halogen alkyl hydrines, hydroxyalkyl sulphates, hydroxyalkyl sulphonates, alkyl anoxides or dihalogen hydrocarbons. The N-hydroxyalkyl compounds of the present invention can be produced as the final process step, if necessary by hydroxyalkylation of corresponding pyrrole or pyridine carboxy aryl amides followed by hydration in accordance with the procedure described in the Swedish Patent Specifications cited above.

Stereoisomers of the optically active amides can be manufactured by using the optically active pyrrolidine or piperidine carboxylic acid which, through further synthesis, gives the optically active final product desired. Alternatively the optically active steroisomers can be separated out by forming salts with optically active acids.

The following Examples serve to illustrate the synthesis of a selection of compounds of the present invention.

11 g of D,L-piperidine-.alpha.-carboxy-2,6-dimethylanilide is dissolved in 150 ml pure alcohol, placed in a 200 ml autoclave, an cooled down to -60.degree. C. 4 g ethylene oxide is added and caused to react in the closed autoclave for 24 hours at room temperature. The alcohol is then evaporated off and the remaining distillate is obtained in the form of a yellow oil. This oil is then fully dissolved, without previous purification, in 100 ml methyl ethyl ketone and the requisite amount of dry HCl gas is added. The hydrochloride of DL-N-(2-hydroxyethyl)pipecolinyl-2,6-dimethylanilide (see formula II) is crystallized out with the aid of graft crystals. 11 g final product was obtained having a melting point 247.degree.-248.degree. C. Equivalent weight 313.3 (theoretical weight 312.8).

23.1 g of D,L-piperidine-.alpha.-carboxy-2,6-dimethylanilide is dissolved in 100 ml pure alcohol and mixed in a sealed reactor with 10 g potassium carbonate and 5 g 2-bromine-ethyl hydrine after which the mixture is slowly heated to boiling point over 10-12 hours. The mixture is filtered to remove potassium bromide and excess carbonate formed at 60.degree. C. and washed with 20 ml heated, pure alcohol. The cleaning and filtering is performed with about 3 g active carbon and the alcohol evaporated off. The distillation residue consists of about 25 g DL-N-(2-hydroxyethyl)pipecolinyl-2,6-dimethylanilide (II) which is converted to the hydrochloride in accordance with Example 1 by dissolving the residue in ethyl methyl ketone and introducing dry HCl gas. The purified final product has a melting point of 247.degree.-248.degree. C.

12 g D,L-piperidine-2-carboxy-2,6-dimethylanilide is dissolved in 100 ml pure alcohol and mixed in a sealed reactor with 10 g potassium carbonate and 6 g 3-bromine propanol. It is then reacted as described in Example 2. 10 g purified N-(3-Hydroxypropyl)-pipecolinyl-2,6-dimethylanilide is obtained, from which the hydrochloride is produced. The product has a melting point of 258.degree. C.

The procedure of Example 1 or 2 is used to produce the optically active stereoisomers. The starting material is either the D(-)- or L(+)-amides instead of racemic, D,L-piperidine-.alpha.-carboxy-2,6-dimethylanilide. A final product corresponding to D(-)- or L(+)-N-(2-hydroxyethyl)-pipecolinyl-2,6-dimethylanilide hydrochloride is obtained and has an optical activity of [.alpha.].sub.D.sup.25 and +19.degree.5' for the D(-) and L(+) forms. The L(+) form has a melting point of 217.degree. C.

15 g N(2-hydroxyethyl)pipecolinyl-2,6-dimethylanilide (base) and 15 g methyl iodide is reflux in 150 ml boiling acetonitrile for 1 hour. After evaporation and stirring with a glass rod a crystalline residue is obtained which is washed with acetone. The final product consists of 13.5 g N-(quaternary-2-hydroxyethyl-N-methyl)pipecolinyl-2,6-dimethylanilide (VIII) which has a melting point of 157.degree. C.

Table 1 lists the properties of some compounds in accordance with the present invention.

N-(2-hydroxyethyl)pipecolinyl-2,6-dimethylanilide (II) which is sometimes referred to herein as S-1249 has been found to have an LD.sub.50 value of 57 mg/kg (lidocaine 28 mg/kg and mepivacaine 31 mg/kg) in experiments with mice (NMRI, .male. 22-25 g).

S-1249 produced convulsions in experiments with conscious rats when 103.+-.8 mg/kg was given intraveneously (5.0 mg/mg/min; N=10. The letter N is used herein to indicate the number of injections given. In parallel experiments similar convulsions occurred with 39.+-.2 mg/kg (N=10) using lidocaine and 38.+-.3 mg/kg (N=10) using mepivacaine. In experiments on rabbits, S-1249 has been found to cause considerably less tissue irritation using the trypan-blue test than lidocaine and mepivacaine after intracutinous injection as can be seen from the results in Table 2.

In experiments on guinea pigs, S-1249 has been found to have a local anaesthetic effect of the same order of magnitude as lidocaine and mepivacaine after intracutaneous infiltration, as can be seen from the results in Table 3.

In experiments with rats, S-1249 has been found to have an equivalent local anaesthetic effect to lidocaine and mepivacaine after perineuronal injection close to the sciatic nerve, as can be seen from the results in Table 4.

In experiments with anaesthetized dogs, S-1249 has been found to have effects equivalent to lidocaine and better than mepivacaine against arrhythmic heart-beats induced by ouabain, as can be seen from the results in Table 5:

In view of its low toxicity, the substance S-1249 has considerably greater therapeutic potential than lidocaine or mepivacaine, both as local anaesthetic and as heart arrhythmic agent.

N-(3-Hydroxypropyl)pipecolinyl-2,6-dimethylanilide (IV) herein sometimes referred to as S-1265 has been found to have an LD.sub.50 value (IV) of 40 mg/kg (lidocaine 28 mg/kg and mepivacaine 31 mg/kg) in experiments with mice (NMRI, .male. 22-25 g).

In experiments on conscious rats, S-1265 gave CNS effects (convulsions) when 80.+-.4 mg/kg was administered intravenously (5.0 mg/kg/min; N=10). In parallel experiments, similar convulsions occurred when using 39.+-.2 mg/kg (N=10) lidocaine and 38.+-.3 mg/kg (N=10) mepivacaine.

In experiments on guinea-pigs, S-1265 proved to have better local anaesthetic effect than lidocaine after intracutaneous infiltration, as can be seen from the results in Table 6:

In experiments with anaesthetized dogs, S-1265 has been found to have effects equivalent to lidocaine and mepivacaine against arrhythmic heart-beats induced by ouabain, as can be seen from the results in Table 7:

In view of the results of the toxicity test, the substance N-(3-hydroxypropyl)pipecolinyl-2,6-dimethylanilide has considerably greater therapeutic potential than lidocaine or mepivacaine, both as a local anaesthetic and as an antiarrhythmic agent.

L-N-(2-hydroxyethyl)prolyl-2,6-dimethylanilide (IX) herein sometimes referred to as S-1258 has been found to have an LD.sub.50 value (iv) of 110 mg/kg (lidocaine 28 mg/kg and mepivacaine 31 mg/kg) in experiments with mice (NMRI, .male. 22-25 g).

In experiments on conscious rats, S-1258 gave CNS effects (convulsions) when 130.+-.10 mg/kg was administered intravenously (5.0 mg/kg/min; N=10). In parallel experiments, similar convulsions occurred when using 39.+-.2 mg/kg (N=10) lidocaine and 38.+-.3 mg/kg (N=10) mepivacaine.

In experiments on guinea-pigs, S-1258 proved to have better local anaesthetic effect than lidocaine after intracutaneous infiltration, as can be seen from the results in Table 8.

In experiments with anaesthetized dogs, S-1258 has been found to be effective against arrhythmic heartbeats induced by ouabain, as can be seen from the results in Table 9:

In view of the results of the toxicity test, the substance L-N-(2-hydroxyethyl)prolyl-2,6-dimethylanilide has greater therapeutic potential than lidocaine and mepivacaine both as local anaesthetic and as antiarrhythmic agent.

N(quaternary-2-hydroxyethyl-N-methyl)pipecolinyl-2,6-dimethylanilide (VIII) herein sometimes referred to as (N-methyl-S-1249) has been found to have an LD.sub.50 value (iv) of 84 mg/kg (lidocaine 28 mg/kg and mepivacaine 31 mg/kg in tests performed earlier) in experiments with mice (NMRI, .male. 20-24 g).

In experiments on conscious rats, N-methyl-S-1249 gave CNS side effects (convulsions) only after 125 mg/kg had been administered intravenously (5.0 mg/kg/min; N=10). In parallel experiments similar convulsions occurred when using 39.+-.2 mg/kg (N=10) lidocaine and 38.+-.3 mg/kg (N=10) mepivacaine.

In experiments on guinea-pigs, N-methyl-S-1249 was found to give local anaesthetic effect after intracutaneous infiltration, as can be seen from the results in Table 10:

In experiments with anaesthetized dogs, N-methyl-S-1249 has been found to have rhythm-regularizing effects against arrhythmic heart-beats induced by ouabain, as can be seen from the results in Table 11:

In view of its low toxicity, therefore, the substance N(quaternary-2-hydroxyethyl-N-methyl)-pipecolinyl-2,6-dimethylanilide has greater therapeutic potential than lidocaine or mepivacaine, particularly as a heart antiarrhythmic agent.

In clinical use the substances under consideration can be administered topically, perorally or parenterally, for instance by injection or by infusion in the form of one or more active components either in the form of a free base or as a pharmaceutically acceptable salt such as hydrochloride, lactate, acetate, sulphamate in combination with a pharmaceutically acceptable carrier or diluent. These pharmaceutical preparations are also included in the invention. The active component or components normally constitute(s) from 0.01 to 0.20 percent by weight of the pharmaceutical preparation.

Solutions for parenteral administration by injection can be prepared as liquid preparations of water-soluble, pharmaceutically acceptable salts of the active component or components. These solutions may also include stabilizing agents and/or buffers and/or agents which prolong or reinforce the biological effects of the active substance(s), such as catechol amines, vasocontracting agents, dextranes, surface active agents or stabilizing fat emulsions.

Preparation of rectal administration can be produced in the form of suppositories, lotions or gels containing the active substance(s) mixed with a neutral fat-base. The preparations may also be manufactured as gelatin capsules containing the active substance(s) mixed with a vegetable oil or paraffin oil. The rectal preparations may also contain substances to prolong or reinforce the biological effects of the active substance(s), such as vasocontracting agents, surface-active agents or steroids.

Preparations for topical administration can be manufactured as solutions, lotions or gels and these preparations may also include stabilizing agents and/or buffers and/or agents to prolong or reinforce the biological effects of the active substance(s), for instance alcohols, surface-active agents or vasocontracting agents.