CA1118350A

CA1118350A - Local anesthetic mixture for topical application, process for its preparation, as well as method for obtaining local anesthesia

Info

Publication number: CA1118350A
Application number: CA000317179A
Authority: CA
Inventors: Berndt F. J. Broberg; Hans C. A. Evers
Original assignee: Astra Lakemedel AB
Current assignee: Astra Lakemedel AB
Priority date: 1977-12-01
Filing date: 1978-11-30
Publication date: 1982-02-16
Also published as: MY8500061A; ATA859578A; FI783668A; AU525417B2; DK154187C; NZ189026A; DK538978A; FI68173B; NO149913C; IE782350L; AT364451B; SE7713618L; IE47682B1; SG8484G; US4562060A; US4529601A; EP0002425B1; HK43284A; JPS54101414A; NO149913B

Abstract

Abstract of disclosure The present invention relates to pharmacological active preparation, especially local anesthetic preparation and deals with the problem of i a obtaining a solution of a local anesthetic agent in the form of its base, where the concentration is higher than otherwise possible. This pro-blem has been dissolved according to the present invention thereby that one local anesthetic agent is the form of its base and as such having a melting point of 30 to 50°C.
preferably prilocaine or tetracaine, is provided with one other local anesthetic agent in the form of its base and as such having a melting point of above 30°C. preferably above 40°C. preferably bensocaine, lidocaine, bupivacaine, mepi-vacaine, etidocaine or tetracaine which agents when brought and heated together form a homogenous oil having a melting of preferably below 40°C. more preferably below 25°C.

Description

~i~8350 Astra L~ikemedel AB
Sodert~ilje/Sweden InventDrs: B F J Broberg, H C A Evers KA 54q-1 UI/ka Local anesthetic mixture for topical applicatinnJ process for its preparation, as well as method for obtaining local anesthesia :
The present invention relates to a mixture of local anesthe-tically active compounds in base form ;n order to obtain topical anesthesia through skinJ process for its preparation, and method for obtaining topical local anesthesia, S
The object of the present invention is to obtain a possi-bility of utilizing local anesthetically active compounds in base form and to obtain a maximal concentration of active substance at the application nn skin in order to obtain local anesthesia with as low a dose as can be.

It is previously known, e g by Swedish Patent S/N 352 239 to produce a local anesthetically active film comprisin~

, ' ~ .

~183~0 lidocaine in crystallized, microdisperse form. The film is hereby intended to be used for anesthesia of mucnus mem-branes, especially in the mouth cavity for blocking the nerves around the teeth in order to facilitate smaller incisicns. Lidocaine is present in the film in ? to 40 %
by weight. The drawback of said solid carrier is that an exactly adjusted dose can not be obtained to penetrate as one can not judge in the single case how rnuch of lidocaine is left in the film carrier. The concentration of lidocaine can as easily understood, neither become so high, which results in that higher doses than necessary rnust be used.

It is further known to combine two or more local anesthetics in the form of acid addition salts in aqueous solutions for injection. (Cf Oritish Patent Specification S/N 1 360 fl20).
In such case the active agents are present in watersoluble form and do not form a homogenous oil.

Previously, the problem has also been to utilize local anesthetically active compounds in the form of their bases as these are in crystalline form at room temperature and acceptable effect is not obtained when the substance is applied in crystalline form.

The wish has than been to obtain an oil phase, containing high amount of local anesthetic, which, by means of a simple carrier, easily can be applied on the intended sur-face.

It has now surprisingly been found that it is possible to obtain such a form by means of the present invention. where-by moreover, a more deep penetrat;ve effect as well as an improved local anesthesia is obtained, whereby the inven-tion is characterized in that one local anesthet;c agent in the form of its base and as such having a melting point of 30 to 50 C is mixed with one other local anesthetic agent in the form of its base and as such having a melting point of above 30C, preferably above 40C.

~1183E~0 According to a preferred embodiment of the invention pri-locaine or tetracaine in base form is mixed with one of benzocaine, lidocaine, bupivacaine, mepivacaine, or etido-caine or tetracaine in base form. It is evident that when tetracaine is used as first base it can not be used as second base.

According to a preferred emhodiment prilocaine and benso-caine are mixed in a weight ratio of 65:35 to 80:20, pre-ferably 70:3Q-According to 2 preferred embodiment prilocaine and lidocaineare mixed in a weight ratio of 42:58 to 80:20J prefer~bly 47:53 to ~:38.
According to another preferred embodiment prilocaine and etidocaine are mixed in a weight ratio of 55:45 to 95:5, preferably 60:40 to 80:20.

According to a further preferred embodiment prilocaine and mepivacaine are mixed in a weight ratio of 8n 20 to ~7:3, preferably 85:15 to 90:1n.

Accordingto another, further preferred embodiment prilocaine and bupivacaine are mixed in a weight ratio of 72:28 to 97:3, preferably 78:22 to 88:12.

According to another preferred embodiment of the invention : tetracai.ne and lidocaine ;n their base forms are mixed in a weight ratio of 4n:60 to 70:3n, pre-ferably 45:5~ to 55:45, most preferably 50:50.

In accordance with the invention a) a local anesthetic agent in the form of its base is mixed with b) one other local anesthetic agent in the form of its base, whereby the agent under a) has a melting point of 30 to 50C and the agent under b) has a melting point of above i1~8350 30C preferably above 40C.

Comoounds under a) are prilocaine, tetracaine, butanilicaine and trimecaine Compnunds under b) are bensocaine, lidocaine, bupivacaineJ
dibucaine, mepivacaine and etidocaine, as well as tetracaine, butanilicaine and trimecaine.

l~lhen the local anesthetic a~ents of a) and b) respectively in base, crystalline form are mixed together and heated the mixture shall have a resulting melting temperature of below 40 C and thereby form a homogenous oil. The oil is complet-ely reformed if heated to the melting point even after a storage at low temperature for long time.

The above given weigllt ratios give mixtures which melt at ternperatures below 40C and are present in the form of an o i 1 .
According to another aspect of the present invention a method for obtaining local anesthesia by means of topical application on skin, whereby a mixture of prilocaine or tetracaine in the form of its base, and any of the compounds ensocaine, lidocaine, bupivaca;ne, r-epivacaine, etidocaine or tetracaine in a therapeutically effective amount is aoplied onto the skin surface through which anesthesia is to be obtained.

3n According to a preferred embodimLnt the mixture is added in a dose of 0.5 to 10 mg/cm of skin, The expression skin above relates to mucous membrane as well as intact or wounded skin.
According to another aspect of the invent-ion injectable compositions are obtained, which injectable compositions contain in oil form one local anesthetic agent in base form ~B3S~

and as such having a melting point of 30 to 5~C, and one other local anesthetic agent in base form and as such having a meltin~ point of above 30C, preferably above fin c~

/
/
/

~8350 Such a composition will have a potent clinical use in more rapid onset of effect and/or prolonged duration of local anesthetic effect.

Above given compounds except for bensocaine and tetra-caine are represented by the general formula ~NHC~R 1 wherein Rl is ~ N ~

CH2CH3 ~CH2CH3 CIHNHCI~2CH2CH3; 2N\ ; or -CHN j and R2 is hydrogen OI' methyl, whereby R? is hydrogen when Rl is -CHNHCH2CH2CH3 Bensocaine, 4-aminobenzoic acid ethyl ester, has the formula _ _ .

H2N~ ~ CnOC2H5 Tetracaine, 2-(dimethylamino)ethylester of p-butylaminoben-soic acid has the formula CH3(CH2)3NH ~ 3--CObCH2CH2N(CH3)2 l-methyl-2-(2,6-xylylcarbamoyl)piperidirle is known under the generic name mepivacaine and is sold under the trade mark Carbocaine 1-butyl-2-(2,6-cylylcarbamoyl)piperidine is known under the generic name bupivacaine and is sold under the trade mark Marcaine~

2-propylamino-N-(2-tolyl)propionamide is known under the generic name prilocaine and is sold under the trade mark Citanest~

Diethylaminoacet-2,6-xylidide is known under the generic name lidocaine and is sold under the trade mark Xylocaine~
2-ethylpropylamino-2,6-n-butyroxylidide is known under the generic name etidocaine and is sold under the trade rnark Duranest~

Prilocaine has a melting point of 3BC: lidocaine a melting point of 6~ C; etidocaine a melting point of 88C; mepiva-caine a melting point of 155C; bupivacaine a melting point of 110C; bensocaine a melting point of B9C tetracaine a melting point of 41C, butanilicaine a melting point of 45--46C, trimecaine a rrielting point of 44C, and dibucaine a melting point of 65C.

Above given mixtures have a melting point minimum within the given ranges. The mixtures form eutectic mixtures, with eutectic rninima.

The oil formed by the local anesthetically active compounds in the form of their bases can be administered as such, or be transferred onto a carrier such as paper, or be intro-duced into a li~uid carrier in order to form an emulsion,or as an emulsion in an ointment base. The different forms of preparation, depend on where one wants to obtain an-esthesia.

il~83SO

After anesthesia through the skin the following incisions can be made.

~ucous membrane: the taking of a punch biopsy, smaller in-cisions in underlying mucous membrane, e v curettage, or gingivectomi or tooth tartar removal, eliminat;on of needle prick pain at an injection. Otholaryngological in-cisions in nose and throat, e g biopsy or trepanation.

Paracentesis of drum-membrane.

Sample excision in the urogenitalic area.

Local anesthesia of cervix at deliverv.
Intact skin: Smaller cutaneous incisions e g biopsy, or excision of naevi, elirnination of needle prick pain before injection.

The present invention will in the following be described more in detail with reference to a number of examples.

Example 1 Prilocaine, base 52 g Lidocaine, base The two local anesthetically active compounds ;n crystalline form were wei~hed together and heated to 30C, whereby the two compounds melted and formed a homogenous oil. The mixture of crystals has a melting po;nt of ~2C. The mixture did not crystalli~e even for very long time of storage at strong cold, when reheated to ?~C.

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ii~8350 F a~le 2 Prilocaine, base 70 g Etidocaine, base 30 ~
100 g The two lncal anesthetically active compounds, in crystal-line form, were weighed together and were treated to 35C, whereby the two compounds melted and formed a homogenous oil. The melting point of the mixture is 29C.

Example 3 Prilocaine, base 85 g Mepivacaine, base 15 g 100 g Ths two local anes~hetically active compounds in crystalline form, were weighed togethér and were heated to 40C, where-by the two compounds melted and formed a homogenous oil.
The melting point of the mixture is 33C.
: ~ :
~ Example 4 :;
25 Prilocaine, base 30 g upivacaine, base 20 g lOD g The two local anesthetically active compounds, in crystal-line form, were weighed together and heated to 40C, where-by the compounds melted and formed a homogenous oil. The melting point of the mixture is 34C.
.
Example 5 Prilocaine, base 70 g ~ensocaine, base 30 g 100 g ~18350 The two local anesthetically active compounds, in crystal-line form, were weighed to~ether and were heated to 35C, whereby the compounds melted and formed a homogenous oil.
The melting point is 29C.

_ ample 6_ Tetracaine, base 50 g Lidocaine, base 50 g 100 g The two local anesthetically active compounds, in crystal-line form, were mixed to~ether and were then heated to 25C, whereby the compounds melted and formed an homo-genous oil. The melting point of the mixture is 17C.

Example 7 -A mixture according to Example 1 was applied onto a carrier of paper in an amount of 1.5 mg/cm2. The carrier, 1 cm2, with the mixture was applied on the teeth gums in the vicinity of the root point of the tooth to be treated, prior to a deep cavity preparation in a vital tooth. After about 5 min the treatment could be carried out without giving the ~:; 25 patient any pain sense.
, ~ j Lidocaine and prilocaine alone do not give such an anEsthe-tic effect.

; 30 The mixtures prepared shall preferably be present in oil form at temperatures about 40C and below.

Biological effect The biological effect of the local anesthetic mixture of the present invention was determined`in an experiment~l investigation of dermal analgesia by epidermal application ~.

1~183SO

of different local anesthetic formulations.

In the present investigation it was shown in 12 volunteers that the pain response, induced by pin-pricking, was part-ly blocked by epidermal application of different localanaesthetic formulations. Dermal analgesia (tested by pin-pricking) was most pronounced with a formulation con-sisting of a eutectic mixture of lidocaine base and pri-locaine base, in a total concentration of 10 %, as an aqùeous emulsion. The other two tested formulations, con-taining lO % lidocaine and 10 % prilocaine base respec-tively, were less effective, with regard to dermal anal-gesia, even if these produced some demostrable effects, different from a placebo emulsion.
Material and method 12 healthy medical students from the Uppsala University Hospital took part in the study.
Pre-formed pads, consisting of cellulose fibres, 2 times 2 centimetres, were soaked by a standardized procedure in either an emulsion containing 5 % lidocaine base l 5 % pri-locaine base, an emulsifying agent and water, 10 % lido-caine base in the same vehicle, lO % prilocaine base in thesame vehicle, or a placebo emulsion containing the emul-sifying agent and water only. On one forearm of the volun-teer the four different emulsions were applied under ; ~ occlusive dressings consisting of impervious tape, while on the other arm the four emulsions were applied under a non--occlusive dressing, using surg;cal tape (3M). A certain distance bstween the application areas was chosen in order to avoid any risk of interference between them.

On the arms of the volunters 11 and 12 the emulsions were applied directly to the skin, with no cellulose pads, but with occlusive and non-occlusive dressings applied as in ~1183SO

the other volunteers.
me application time for the pads was 60 minutes.
Immediately after removal of the pads, the square areas under the two types of dressing were marked at the edges. A line was also marked with-in each applied area dividing them into two identical triangles. One of these surfaces were then used for the pin-prick experiments, the other for studying other effects.
Testing of dermal analgesia The pin-pricking prooedure was carried out with disposable dental needles. In each of the test areas 10 pin-pricks were made. 10/10 repre-sents full analgesia, 0.10 no analgesia.
Results The lidbcaine-prilocaine emulsion was found to be significantly more effective than the lidocaine emulsion, the prilocaine emulsion and the placebo emulsion in producing dermal analgesia. By the student's t-test it was found that:
Lidocaine-prilocaine versus placebo: p = 0.001 ~ Under Lidocaine-prilocaine versus lidocaine: p = 0.001 ~occlusive Lidocaine-prilocaine versus prilocaine: p = o.01J bandage Lidocaine-prilocaine versus plaoebo: p = 0.01 l Under non-Lidocaine-prilccaine versus lidocaine: p = 0.01 ~occlusive Lidocaine-prilocaine versus prilocaine: p = o.01J bandage The lidocaine and prilocaine emLlsions were found to be insignific-antly more effective than the place~o emulsion under occlusion as well as insignificantly different in effect to placebo under a non-occlusive bandage, as evident frcm Table I, statistical data, below.

~1 Table I
___ Pin-prick _ _ .

nccl_sion on-occluslon L-P L P Placebo L-P L P Placebo

3 2/10 0/10 0/100/10 0/10 0/10 0/10 0/ln 410/10 5/10 10/100/10 10/10 0/ln fi/10 0/10 6 R/10 2/10 n/100/10 9/10 0/10 0/10 0/10 810/10 n/10 2/100/10 8/10 0/ln 0/10 0/10 10n/lo 0/10 0/100/10 n/lo o/ln n/ln ~/10 Ml_lo7-40 1.40 1.440.40 5.10 0.10 0.70 0.20 -127.R2 2.33 2.640.30 4.92 0.08 0.75 0.17 Statist _ 1 data Patients No 1-10 L-P/placebo:t = 5.7R~ L-P/placebo:t = 3.4 l-P/L:t = 5.87~ L-P/L:t = 3.70 L-P/P:t = 11.33~ L- P/P: t = 3.50 1-12 L-P/placebo:t = 7.11~ ~ L-P~Placebo:t = 3.9fi~
L-P/L:t = 6.03**~ L-P/L:t = 4.29~*
L-P/P:t = 4.30~ L-P/P: t = 3.97*~

Tab].e I

Pin_prick Occlus _ Patients No 1-10 L/placebo:t = 1.~8 n s P/placebo:t = 0.80 n s 1-12 L/placebo:t = 2.32~
P/place~o:t = 1.71 n s Non-occlusion 1-10 L/placebo:t = 0.42 n s P/placebo:t = 0.76 n s 1-12 ~/placebo:t = 0.43 n s P/placebo:t = l.O5 n s 1 ~
L-P = lidocaine-prilocaine comp L = lidocaine comp P = prilocaine comp .

.

~1~83SO

It has also been shown that the present combinations of local anesthetics possess worthwile prnperties in in-hibitin~ perspiration. They can thus be used in antiper-spirant compositions as emulsions for roll-on, or emul-sions or solutions fDr spraying.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Process for the preparation of local anesthetically active prepara-tions which contain the active component as an oil, characterized in that a local anesthetic agent in the form of its base and as such having a melting point of 30 to 50°C is mixed with one other local anesthetic agent in the form of its base, and as such having a melting point of above 30°C.

2. Process according to claim 1 characterized in that prilocaine or tetracaine in the form of its base is provided with one of the compounds benzocaine, lidocaine, bupivacaine, mepivacaine, etidocaine or tetracaine in the form of its base.

3. Process according to claims 1 to 2, characterized in that the local anesthetic mixture has a melting point of below 40°C.

4. Process according to claims 1 to 2, characterized in that the local anesthetic mixture has a melting point of below 25°C.

5. Process according to claim 2, characterized in that prilocaine and bensocaine are mixed with each other in a weight ratio of 63:37 to 96:4.

6. Process according to claim 5, characterized in that the weight ratio is 65:35 to 80:20.

7. Process according to claim 2, characterized in that prilocaine and lidocaine are mixed with each other in a weight ratio of 42:58 to 80:20.

8. Process according to claim 7, characterized in that the weight ratio is 47:53 to 62:38.

9. Process according to claim 7 characterized in that the weight ratio is 55:45.

10. Process according to claim 2, characterized in that prilocaine and etidocaine are mixed with each other in a weight ratio of 55:45 to 95:5.

11. Process according to claim 10, characterized in that the weight ratio is 60:40 to 80:20.

12. Process according to claim 2, characterized in that prilocaine and mepivacaine are mixed with each other in a weight ratio of 80:20 to 97:3.

13. Process according to claim 12, characterized in that the weight ratio is 85:15 to 90:10.

14. Process according to claim 2, characterized in that prilocaine and bupivacaine are mixed with each other in a weight ratio of 72:28 to 97:3.

15. Process according to claim 14, characterized in that the weight ratio is 78:22 to 88:12.

16. Process according to claim 2, characterized in that tetracaine and lidocaine are mixed with each other in a weight ratio of 40:60 to 70:30.

17. Process according to claim 16, characterized in that the weight ratio is 45:55 to 55:45.

18. Local anesthetic preparation for topical or parenteral application characterized in that it comprises as active component one local anesthetic agent in the form of its base and as such having a melting point of 30 to 50°C, and one other local anesthetic agent in the form of its base and as such having a melting point of above 30°C, which agents when brought and heated together form a homogenous oil, which has a melting point below 40°C.

19. Local anesthetic preparation according to claim 18 characterized in that prilocaine and lidocaine are mixed with each other in a weight ratio of 47:53 to 62:38.

20. Local anesthetic preparation according to claim 19 characterized in that the weight ratio is 55:45.