Agents for distributing gallstones

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an agent for disintegrating gallstones, and more particularly to an agent for disintegrating gallstones containing an alkali metal carbonate or a combination of an alkali metal carbonate and N-acetylcysteine as its effective components.

2. Related Arts

The statistical study shows that gallstone carriers reach about 9% of the population in Japan. In 1989, the cholecystolithiasis patients were reported to be 270,000, most of whom were subjected to surgical lithectomy. The gallstones are classified into cholesterol gallstones and pigment gallstones (bilirubin calcium and black-pigment stones) based on the component thereof. Studies on an agent for dissolving gallstones have been performed for a long time, resulting in the development of formulations of bile acid such as ursodeoxycholic acid and chenodeoxycholic acid for dissolving choresterol gallstones. Clinical tests have proved that such formulations are effective for gallstone dissolution. However, actual effect for gallstone dissolution given by such formulations depends on the size of the stone and cholecyst function, whereby the patient should be dosed for a long period such as a half- year to a year or more. A suitable agent for dissolving pigment stones has not yet been developed in spite of various studies.

The inventor has found out from studies on composition of the gallstones that mucopolysaccharides and mucoproteins (hereinafter abbreviated to muco-substances) play an important role as a component for binding the crystalline cholesterol or bilirubin. On the other hand, SH-compounds including N-acetylcysteine have been known to have action for splitting off the S--S bond of muco-substances. In particular, it has been reported that N-acetylcysteine accelerates dissolution of cholesterol gallstones [see Scand. J. Gastroent., 24, 373-380 (1989); Gastroenterology., 98, 454-463 (1990)]. However, this document reports that the dissolution of cholesterol gallstones takes about 10 hours to several weeks, and further that the absolute effect is small.

On the other hand, the effective action of alkali metal carbonates for disintegrating gallstones has not been known.

Under such circumstance, it is desired to develop an agent which can easily destroy gallstones to make their small pieces which can be removed without surgical lithectomy.

SUMMARY OF THE INVENTION

The invention provides an aqueous solution comprising an alkali metal carbonate or its combination with N-acetyl-cysteine.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Examples of the alkali metal carbonates include sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate or the like, among which monoalkali metal carbonate is preferable, and especially sodium hydrogen carbonate is more preferable. Preferably, the concentration of the alkali metal carbonate in the aqueous solution is 1 to 30% (W/V) (represented by weight per volume hereinafter), more preferably 5 to 20%, for example, 8%, 10% or 12%.

Suitably, N-acetylcysteine is contained in the aqueous solution at the concentration of 5 to 30%, preferably 10 to 25%, for example, 10%, 15% or 20%.

Suitable medium for the aqueous solution is distilled water, particularly sterile water.

The aqueous solution as the agent for disintegrating gallstones of the present invention is observed to have pH 7 to 10, preferably 7.5 to 9. The aqueous solution may be adjusted by adding an acid or an alkali when it does not exhibit the above mentioned pH range with only effective components.

The dose of the agent for disintegrating gallstones according to the present invention varies with the age of patient, level of disease or the like, but generally 1 to 100 ml per one time for an adult. The administration methods include the following: a method in which the agent is infused or perfused into a bile duct or gallbladder through a tube which is left at the surgery; a method in which the agent is infused into a bile duct through a T-tube inserted into the bile duct at choledocholithotomy; or a method in which the agent is retrogressively infused into a gallbladder or bile duct from duodenal mamilla part under endoscopy.

N-Acetylcysteine used for the present invention exhibits remarkably high safety, since it is clinically used for human being as an agent for protecting liver or an expectorant. The sodium hydrogen carbonate, which is representative of the alkali metal carbonate, is clinically employed as ulcer-preventive agent. Accordingly, the agent for disintegrating gallstones of the present invention exhibits high safety.

The present invention will be specifically explained hereinafter with reference to the Experiments and Examples. The percentage hereinbelow represents W/V %.

Experiment 1

Action for Disintegrating Gallstones

Gallstones (54.9 .+-.6.8 mg) nearest in shape, material and size were obtained from a single patient for this Experiment. The obtained gallstones were black-pigment stones having a rough structure and containing a number of muco-substances. 20% of N-acetylcysteine were respectively added to distilled water and 10% sodium hydrogen carbonate to obtain respective test solutions 1 and 2. On the other hand, a test solution 3 containing only 10% sodium hydrogen carbonate and a test solution 4 (control) containing only distilled water were prepared. One stone of the obtained gallstones was put into each test solution for observing the number of a piece of the stones by taking pictures thereof every five minutes. Table 1 shows the degree of the gallstone disintegration.

TABLE 1 ______________________________________ Number of Pieces of Stones with Time Test 40 Solution 0 5 10 15 20 25 30 35 (min.) ______________________________________ 1 1 1 14 24 47 113 129 143 174 2 1 1 13 52 256 332 389 423 450 3 1 41 58 123 180 185 203 230 315 4 1 1 1 1 1 1 1 1 1 ______________________________________

As is apparent from Table 1, gallstone disintegration was observed in test solutions 1 to 3 except for distilled water (control test solution 4). In particular, gallstone disintegration was remarkably observed in the test solution 2 in which N-acetylcysteine was added to 10% sodium hydrogen carbonate compared to the test solutions 1 and 3.

Experiment 2

Under the same conditions as in the Experiment 1, gallstone disintegration was observed using a test solution 5 containing 10% potassium hydrogen carbonate and a control test solution 6 containing 10% sodium hydroxide. The results were shown in Table 2.

TABLE 2 ______________________________________ Test Number of Pieces of Stones with Time Solution 5 10 15 20 25 30 35 40 (min.) ______________________________________ 5 22 43 68 84 103 112 126 166 6 1 1 1 1 4 8 11 15 ______________________________________

Gallstone disintegration was rarely observed in the control test solution 6.

Experiment 3

Under the same conditions as in the Experiment 1, the Experiment 3 was performed using a test solution 7 in which 20% of N-acetylcysteine was added to 10% sodium hydrogen carbonate (pH 7.5) and a control test solution 8 in which 20% N-acetylcysteine was added to 10% potassium hydrogen carbonate (pH 7.5) for observing the difference caused by the kind of the alkali metal hydrogen carbonate. The results were shown in Table 3.

TABLE 3 ______________________________________ Test Number of Pieces of Stones with Time Solution 5 10 15 20 25 30 35 40 (min.) ______________________________________ 7 6 36 49 88 137 425 465 480 8 14 96 140 268 280 315 340 390 ______________________________________

Experiment 4

Under the same conditions as in the Experiment 1, gallstone disintegration was observed using test solutions 9 to 11 in which 10% sodium hydrogen carbonate was added to 20% N-acetylcysteine solution to find out the effect of pH on gallstone disintegration. Each of the test solutions 9 to 11 varies in pH. Specifically, the test solution 9 is pH 6.0, the test solution 10 is pH 7.5 and the test solution 11 is pH 8.2. The results were shown in Table 4.

TABLE 4 ______________________________________ Number of Pieces of Stones with Time Test 40 Solution 5 10 15 20 25 30 35 (min.) ______________________________________ 9 1 2 4 8 14 16 16 48 (pH 6.0) 10 6 36 49 88 137 425 465 480 (pH 7.5) 11 120 138 169 286 306 328 415 488 (pH 8.2) ______________________________________

The function of gallstone disintegration was remarkably reduced in the solution of at least pH 6.0 compared to the other solutions of different pH but of the same effective components.

Experiment 5

Under the same conditions as in the Experiment 1, gallstone disintegration was observed using test solutions 12, 13 and 3 of 1%, 5% and 10% sodium hydrogen carbonate respectively to find out the effect of concentration of the sodium hydrogen carbonate. The results were shown in Table 5.

TABLE 5 ______________________________________ Test Number of Pieces of Stones with Time Solution 5 10 15 20 25 30 35 40 (min.) ______________________________________ 12 1 5 11 16 18 28 35 38 13 25 50 58 63 73 89 136 145 3 41 58 123 180 185 203 230 315 ______________________________________

The effects on gallstone disintegration were great in the cases of 5% and 10% sodium hydrogen carbonate, particularly 10% sodium hydrogen carbonate.

EXAMPLE 1

Injection for local administration was prepared by mixing the following compositions in accordance with a known method.

______________________________________ N-Acetylcysteine 200.0 mg Sodium hydrogen carbonate 100.0 mg Distilled water Total 300.0 mg (per 1 ml) ______________________________________

The effective components of an agent according to the present invention possess action for rapidly disintegrating gallstones, thereby useful for therapy of cholecystitis.