GB2126478A

GB2126478A - Method of contraception in male mammals

Info

Publication number: GB2126478A
Application number: GB08225296A
Authority: GB
Inventors: Charles M Stagg; Ronald S Tribble
Original assignee: Philips Roxane Inc
Current assignee: Philips Roxane Inc
Priority date: 1979-04-13
Filing date: 1982-09-06
Publication date: 1984-03-28
Also published as: FR2531858B1; GB2126478B; AU556482B2; CA1185183A; DE3229234C2; AU8805182A; JPS5933217A; FR2531858A1; DE3229234A1

Abstract

The injection of solutions of lower carboxylic acids or derivatives thereof is described as a method of chemical castration of or contraception in male mammals with external testes. Solutions containing from 1 to 90% by weight of lactic acid are preferred and are very effective.

Description

SPECIFICATION Method of castration and contraception The invention relates to a method of chemical castration of and contraception in male mammals with external testes. More particularly in this method a suitable preparation may be injected into the vasa deferentia, the testes or the epididymides of the male mammals.

The castration of male mammals may be performed by surgery, but an open wound can lead to complications and infections such as tetanus, and may consequently cause death. As a result of the stress and pain connected with surgical castration, the animals are frequently retarded by at least two weeks in their physical development.

A number of attempts have already been made to perform castration by a chemical method. A number of chemical reagents and mixtures, both natural and synthetic, have been tried. Thus, agents with a sclerotic activity have been applied to the male reproductive organs in order to prevent the passage of semen. All the processes have some disadvantages, manifested by either inefficiency and/ or undiminished libido and/or the formation of uncontrollable necrotic tissue damage.

The testes have two main functions. The first is the production of semen which runs away through the seminiferous tubules and the second is the production of the androgens (testosterone and dihyd rotestosterone) which run away in the interstitial cells (Leydig's cells).

After being produced in the testes, the sperms are released in the top of the epididymis and travel from there to the end of the epididymis, a cavernous network of convoluted tubes. The function of the epididymis is to transport the semen, develop it to maturity, concentrate it and store it. On ejaculation, the spermatozoa are released from the epididymides into the vasa deferentia and finally through the penis to the outside. The function of the two vasa deferentia is to ensure the supply of, gas exchange in and thermo-regulation of the testes via the plexus pampiniformis.

We have now developed a method, employing a suitable agent, which interferes with this complex interplay. In our method, on being injected into the two vasa deferentia, the agent used destroys the vascular system and thus produces atrophy of the testes and hence loss of spermatogenesis and loss of libido.

Alternatively, when injected directly into both testes, the agent causes atrophy and loss of spermatogenesis and libido or, when injected into the epididymides, causes sterilisation (contraception) but leaves the libido undiminished.

According to one aspect of the invention, therefore, we provide a method for the castration of or of contraception in male mammals which comprises injecting into the genital organs of said mammals an effective amount of castrating or contraceptive agent.

The method can be used on a wide range of mammals, provided that it is not restricted by the size and unfavourable shape of the male genitals as is the case in boars, stallions and male cats. It is of particular application on dogs, cattle, sheep and goats.

A particularly preferred agent used in the invention may be selected from an aqueous solution of a mono- or dicarboxylic acid with up to 4 carbon atoms, a hydroxy-substituted analogue or an anhydride thereof. Included amongst the acids which may be used are acetic, propionic, butyric, glycolic, oxalic, malonic, succinic, malic and tartaric acid, acetic anhydride and, more particularly, lactic acid and lactic acid lactide. A 1-90% aqueous lactic acid solution in a dosage of from 0.1 to 20 ml, more particularly from 0.25 to 16 ml has been found to be particularly suitable. A 5 to 85% aqueous lactic acid solution has been successfuily used for the sterilisation of bulls and male dogs. When injected into the vasa deferentia or the epididymides of male dogs, a 5 to 25% aqueous lactic acid solution has proved particularly effective.The lactic acid solutions used showed few side effects and no ulceration whilst giving reproducible results.

Lactic acid is a naturally occurring non-toxic reagent which is also easily detected in tissue samples and residues.

The optimum method of administration has proved to be by injection through the two vasa deferentia, since with this method of injection only a small area is destroyed, as opposed to the entire testes. However, in bull calves weighing less than 45 kg injection into the testes is preferable since the injection can be given more easily and only a little tissue is destroyed. This method of chemical castration can be used particularly successfully and economically in bulls and male dogs. In the U.S.A alone about 20-30 million bull calves per year have to be castrated. The method according to the invention is highly useful for restricting the dog population; it may be used, for example, as an economical method of sterilising male dogs in dog homes.

The method according to the invention has proved to be a safe, rapid, economical, practi cal method which is simple to perform after a single demonstration. The complications which occur in surgical castration do not arise and consequently chemical castration is cleaner, safer and consequently more comfortable. Moreover, the retarded growth which occurs in surgical castration does not happen with chemical castration.In comparison with earlier methods of chemical castration, the invention provides a dosage-dependent effect, high efficiency, the avoidance of uncontrollable tissue damage, versatility in its range of applications, with the possibility of either maintaining or suppressing the libido as required and adaptability for the treatment of different animals, for example by modifying the volume administered and the size of the needle, to suit different animals.

According to a further feature of the invention, we provide an aqueous solution in a form suitable for injection for use in a method as described above. Such solutions may be formulated in, for example, sealed containers from which injectible samples may be taken, or may be prepared from appropriate two-part packs. The aqueous solution will preferably be formulated using high-grade carboxylic acid compound and the water used will desirably be sterile. The solution or pack may also be present in association with a set of instructions for the use thereof in the method of the invention.

The method according to the invention is hereinafter illustrated more fully with reference to the Examples, which should not be taken as limiting.

Example 1 The effect of reagent containing lactic acid was tested on a total of 1 73 bulls weighing between 45 and 286 kg. Different concentrations and volumes of the reagent were injected into both vasa deferentia. As controls, 4 bulls were castrated surgically. 37 of the 1 73 bulls weighed more than 225 kg. The tests showed that better results were obtained when the process was, used on bulls with a body weight of less than 225 kg. Thus, the treatment was successful in 98 out of 1 36 bulls (72%) weighing less tban 225 kg, whereas in the 37 bulls witH a body weight of mote than 225 kg the process was successful in only 24 animals (65%).Moreover, there was found to be a clear dosage-dependent effect proportional to the body weight, and as a result a dose of 2 ml is recommended for bulls weighing up to 90 kg (93% efficiency), a dose of 4 ml (100% efficiency) for body weights from 90 to 135 kg and a dose of 8 ml (82% efficiency) of 85% lactic acid solutions for body weights of from 1 35 to 225 kg.

If the efficiency rate is to be increased, higher doses should be administered.

Example 2 The aim was to determine the most favourable injection site by injecting 8 ml of an 85% lactic acid solution into both vasa deferentia. For this purpose, the substance was injected into the vasa deferentia of 20 bulls, on the one hand directly above the testes and on the other hand 2.5 to 3.75 cm above the testes. The results showed that injection directly above the testes was more favourable, with an efficiency rate of 95, as opposed to 80%.

Example 3 1 and 2 ml of an 85% lactic acid solution were injected directly into the testes of 5 Holstein bull calves (between 0 and 33 days old). The positive results in all the calves show that the process according to the invention can be used even in very young calves.

Example 4 Lactic acid was tested as a possible chemical steriliser for dogs. The results obtained from injecting lactic acid into the epididymides and the plexus pampiniformis of the vasa deferentia clearly show that a 5 to 25% lactic acid solution is an effective chemical steriliser.

For 25, 20, 1 5 and 10% lactic acid, the results show percentage efficiencies of 82% (14 out of 17), 100% (6 out of 6), 92% (12 out of 13) and 80% (4 out of 5).

Claims

1. A method for the castration of or of contraception in male mammals with external testes, which comprises injecting into the genital organs of said mammals an effective amount of a castrating or contraceptive agent.

2. A method as claimed in claim 1 wherein the agent is an aqueous solution of a mono- or dicarboxylic acid with up to 4 carbon atoms, or a hydroxy-substituted analogue or anhydride thereof.

3. A method as claimed in claim 1 wherein the agent is an aqueous solution of lactic acid or the lactide thereof.

4. A method as claimed in any of claims 1 to 3 wherein the mammal is a bull, cat, dog, sheep, pig, horse or goat.

5. A method as claimed in claim 3, wherein a 5 to 85% lactic acid is injected into the testes of a bull.

6. A method as claimed in claim 3, wherein a 5 to 85% lactic acid is injected into the vasa deferentia of the bull.

7. A method as claimed in claim 3, wherein a 5 to 25% aqeous lactic acid solution is injected into the epididymides of a male dog.

8. A method as claimed in claim 7, wherein the lactic acid solution is injected into the plexus pampiniformis of a male dog.

9. A method as claimed in claim 1 substantially as hereinbefore described.

10. A method for the castration of or of contraception in mammals substantially as hereinbefore described with reference to any of the Examples.

11. An aqueous solution in a form suitable for injection for use in a method for the chemical castration of or of contraception in male mammals with external testes which includes a mono- or dicarboxylic acid with up to 4 carbon atoms, or a hydroxy-substituted analogue or an anhydride thereof.

1 2. A solution as claimed in claim 11, which comprises a 1 to 90% aqueous lactic acid solution.

1 3. A solution as claimed in claim 11 substantially as herein before described or with reference to any of the Examples.