GB2026861A - Pharmaceutical compositions containing 5-methyl-7-diethylamino-S- triazolo (1,5-a) pyrimidine - Google Patents

Abstract

Pharmaceutical compositions preferably in unit dosage form containing 5-methyl-7-diethylamino-S-triazolo (1,5-a)-pyrimidine (Trapidil) are used in the promotion of coronary collaterals in a mammal, for the lowering of blood pressure, the lowering of serum cholesterol, and for the inhibition of the edamatous reaction in the arteries of said mammal.

Description

SPECIFICATION Pharmaceutical compositions containing 5-methyl-7-diethylamino-S-triazolo (I, 5-a)-pyrimidine In Japan, circulatory diseases such as ischemic heart diseases, cerebrovascular disturbance, arteriosclerosis and hypertension are very serious diseases that result in a great many deaths.

For example, ischemic heart disease is caused by insufficient supply of nutrition and oxygen to the ischemic portion in the heart muscles owing to coronary blood flow disturbances (coronary insufficiency) caused by functional and organic changes in the coronary arteries. More than 90% of ischemic heart diseases are caused by stiffening of the coronary arteries.

From the clinical viewpoint, in arteriosclerosis, atherosclerosis affecting elastic arteries such as the aorta, the coronary artery, the basilar artery and the renal artery is important. This atheroscelerosis causes such diseases as celebral arterioscelerosis, heart diseases owing to coronary arteriosclerosis and renovascular hypertension.

There are various theories concerning the cause of arteriosclerosis, for example, (i) that a primary cause is abnormal lipid metabolism wherein the plasma lipid level increases and the lipid is deposited on the artery wall, (ii) that edema and swelling take place in the intima or the stroma of the tissue below the intima and lipid is secondarily deposited on the blood vessel wall in which such edema and swelling have taken place, and (iii) that by enhancement of blood coagulation activity or reduction of fibrinolytic activity, a fibrin layer is deposited on the inner face of the blood vessel wall, which causes initial intima disturbance, and formation of a thrombus is an initial pathosis of arteriosclerosis.It is known that patients with coronary artery disease often exhibit an increase in blood coagulation activity an increase in the adherence of the platelets and a reduction in fibrinolytic activity. Accordingly formation of a thrombus owing to increasing adherence and aggregation of the platelets has recently been noted as an important factor causing arteriosclerosis.

From the clinical and epidemological viewpoints, hypercholesteremia, hypertension and excessive smoking are regarded as three main risk factors of arteriosclerosis. The relation of hypercholesteremia to arteriosclerosis and to ischmic heart diseases has heretofore been examined and reported in various publications. For example, in the epidemiological investigation's in the Framingham Study, U.S.A. [K.

Westlund, Bibl.Nutr. et Diet., 6, 32 (1964)], it was confirmed that serum cholesterol is a very important risk factor in coronary arteriosclerosis and that serum lipid has a very close relation to arteriosclerosis. Further, it was reported that the incidence of ischemic heart diseases in patients given cholesterol lowering agents was significantly lower than that in patients not given such agents [L.R. Krano et al., J. Am. Med. Asso., 219,845 (1962)]. Moreover, a decrease in mortality rate was reported when cholesterol lowering agent was administered to patients suffering from ischemic heart diseases [K.G. Green et al., Progr. Biochem.

Pharmacol., 2,378(1967)].

As apparent from the foregoing, ischemic heart diseases are closely related to arteriosclerosis and they both have a close relation to hypertension.

The causes of hypertension are divided into two; (1 ) causes which induce hypertension, i.e., a factor directly causing elevation of the blood pressure, and (2) the hypertension-maintaining mechanism. In many cases, hypertension is essential hypertension of an unknown etiology, and the occurrence and maintenance mechanism of which are quite complicated. It is assumed that essential hypertension is caused by an upset in the balance among the elasticity of the blood vessel wall, cardiac output, the quantity of blood and the peripheral blood vessel resistance.

Many victims of hypertension die from diseases of the heart, brain and kidney caused by morbid changes in blood vessels owing to hypertension. In Japan, the mortality rate from these diseases complicated by hypertension are higher in the order of brain diseases, heart diseases and kidney diseases. However, recent statistical data indicate that the mortality rate from heart diseases complicated by hypertension has been increasing gradually.

As pointed out hereinbefore, hypertension is one of the significant risk factors in arteriosclerosis. This is also true in case of ischemic heart diseases. This is quite evident from examining the incidence of ischemic heart diseases in hypertensives and people having normal blood pressure, which had been continued for 6 years [W. B. Kannel et al., Ann. Intern. Med., 55, 33 (1961)]. Namely, the incidence of attacks of ischemic heart diseases in male hypertensives is 2.6 times as high as the incidence of attacks in men having normal blood pressure and the incidence of attacks in female hypertensives is 6 times as high as the incidence of attacks in women having normal blood pressure.

As is apparent from the foregoing, ischemic heart diseases, arteriosclerosis and hypertension participate with one another in a very complicated manner, and complications of these diseases are often observed in the clinical cases.

As remedies for these circulatory diseases, a method in which medicines effective against independent diseases are respectively administered has generally been adopted. As a remedy against an ischemic heart disease, e.g., angina pectoris, such medicines have been used that control oxygen consumption in heart muscles and increase the coronary blood flow, such as nitroglycerin, nitrite compounds such as amyl nitrite, ss-blocking agent such as propranolol, and dilthiazem. However, each of these medicines is a symptomatic drug.

For arteriosclerosis, there have ordinarily been used lipid metabolism agents for reducing the serum lipid level or improving the metabolism of serum lipids to prevent the occurrence or development of arteriosclerosis. However, these agents have various defects. For example, the dose is generally high, and troubles are often induced in the stomach, intestines and liver due to long-term administration. In addition, ingestion of these medicines is difficult.

Hypotensive diuretics of the thiazide type have been used as a remedy for essential hypertension occupying 80 to 90 % of hypertension. While these medicines are being administered, the blood pressure is lowered, but the effect does not persist if the administration is stopped. Accordingly, these medicines fail to cure hypertension radically. Further, these medicines product such unfavorable side effects as hypopotassiumia, troubles in the digestive organs and an increase in the uric acid level of the blood, and they are still insufficient and defective as drugs administered for a long period of time.

Since the foregoing circulatory diseases are closely associated with one another, it is not preferred to adopt independent curative means for respective diseases, but it is desired to establish generic and comprehensive remedies for these circulatory diseases.

From this viewpoint, a medicine which can provide a remedy for ischemic heart diseases is desired. This medicine should have not only a direct effect of increasing the coronary blood flow but also an effect of curing or preventing arteriosclerosis which causes coronary insufficiency, as well as a hypotensive effect of preventing or curing hypertension which is a rislcfactor in arteriosclerosis or coronary insufficiency.

Further, a remedy for arteriosclerosis is desired to have effects of controlling various factors which are considered to participate in the occurrence of arteriosclerosis, such as abnormal lipid metabolism, troubles in the stroma of the blood vessel wall and thrombus formation, and also a hypotensive effect of curing or preventing hypertension which is a risk factor in arteriosclerosis and an effect of preventing the attack of ischemic heart diseases which the patient might suffer in the future.

Similarly, a remedy for hypertension is desired to have not only a symptomatic effect but also an effect of preventing or curing arteriosclerosis which is considered to participate in the occurrence and development of hypertension.

THE PRESENT INVENTION From all these consideration, we conducted research with a view to developing a medicine having a generic overall therapeutic effect on circulatory diseases. As a result of this research, it was found that 5-methyl-7-diethylamino-S-triazolo (1 ,5-a)-pyrimidine (generic name of "Trapidil"; hereinafter referred to as "TR") has various activities closely associated with the pathogenic physiology of circulatory diseases, such as a coronary vasodilating activity, collateral formation promoting activity, hypotensive activity, serum cholesterol-reducing activity, an activity of inhibiting edematous redaction in artery, platelet aggregation preventing and an anti-kinin activity. Based on these finds, we have now perfected the present invention.

The objects and advantages of this invention will be better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

Figures 1 and2 are graphs showing the results of Test Example 1.

Figure 3 is a graph showing the results of Test Example 3.

Figure 4 is a graph showing the results of Test Examples.

Figure 5 is a graph showing the results of Test Example 6.

Figure 6 is a graph showing the results of Text Example 8.

Figures 7to 10 are photographs showing the results of Test Example 9.

Figure 11 is a graph showing the results of Test Examples 9.

Figure 12 is a graph showing the results of Test Example 10.

Figure 13 is a part of the ileum contraction curve obtained in Test Example 11.

TR is a known compound having a structure represented by the following formula

This compound is easily soluble in water and organic solvents and has a bittertast, and is found in the form of crystalline powder having a white or lightly yellowish white colour.

The pharmacological activities of TR will now be described in detail with reference to the following Examples.

Test Example 1 Activity ofpromoting formation of coronary collateral.

When a state of coronary insufficiency continues for a certain period, collaterals are formed to compensate for an insufficient coronary blood flow, as is well known in the art. Accordingly, researchers have been seeking a drug to promote the formation of these collaterals as a remedy for ischemic heart diseases. We carried out some experiments to determine the influence of TR on the formation of the coronary collaterals.

Beagles having a body weight of 9 to 12 Kg were used as test animals. A control group and a TR-administered group each consisted of 10 beagles. AfterTR had been orally administered at a dosage of 150 mg/day continuously for about 3 months, an anterior descending branch of the left coronary artery was ligated to form an acute coronary occlusion. Seven days later the dog was sacrificed and the degree of the anastomosis formation between the coronary arteries and the expansion of the infarct were examined.The degree of the anastomosis formation between the coronary arteries was evalulated by counting the number of ultra-large anastomoses (having a diameter larger than 0.5 mm), large anastomoses (having a diameter of 0.3 to 0.5 mm), medium anastomoses (having a diameter of 0.2 to 0.3 mm) and small anastomoses (having a diameter of 0.1 to 0.2 mm) and then adding these numbers. The expansion of the infarct was evaluated by collecting pieces of the muscles of the left ventricle sectionally cut at intervals of about 5 mm in a region from the ligated portion toward the apex of the heart and calculating the ratio of the area occupied by the infarct to the total muscle of the left ventricle in the collected pieces. Administration of TR was continued even after the ligation until the dog was sacrificed.

The results of the examination of the degree of anastomosis formation between the coronary arteries are shown in Figure 1, and results of the examination of the expansion of the infarct are shown in Figure 2.

It was confirmed that the number of the anastomosis between the coronary arteries after formation the coronary occlution was significantly increased by administration of TR for about 3 months. It also was confirmed that the expansion of the infarct was controlled in the TR-administered group as compared with that in the control group. These results are deemed to indicate that the administration of TR is effective for formation of the collaterals due to the anastomoses between the coronary arteries.

Test Example 2 - Hypotensive Effect on Normal Rabbits The blood pressure of a rabbit was recorded on a Kymograph with a mercury manometer connected to the carotid artery. TR or hydralazine was administered from an ear vein. The results are shown in Table 1.

Table 1 Medicine Dosage {mglKg) Blood Pressure Blood Pressure Reduction (mm Hg) Reduction Ratio (%) TR 1 15 12 TR 3 30 25 TR 5 40 35 Hydralazine 0.3 30 25 Hydralazine 1 36 30 TR has an effect substantially equivalent to the effect of hydralazine when TR is administered in an amount which is 5 to 10 times the amount of the hydralazine administered. However, in view of the fact that the clinical dosage of hydralazine is 20 to 40 mg/day and that of TR is ordinarily 300 mg/day, it is considered that the hypotensive effect of TR is clinically substantially equivalent to the hypotensive effect of hydralazine.

Test Example 3 - Hypotensive Effect in Spontaneous Hypertension Rats (SHY) Male SHR 13 to 15 weeks in age and having a blood pressure of 180 to 190 mm Hg were used as test animals. Each TR-administered group consisted of 5 rats. The blood pressure was measured in the unanesthetized state according to the plethysmographic method before and 1 hour after the administration of the medicine. TR was orally administered at a dosage of 30 mg/Kg and 0.9 % physiological saline solution was orally administered to the control group. The results are shown in Figure 3.

Test Example 4 - Confirmation of Hypotensive Activity in Men TR or propranolol (PR) was orally administered for 2 or 4 weeks to ischemic heart disease patients. The dosage of TR was 100 mg X 3 times a day and the PR was 20 mg X 3 times a day. These patients were divided into two groups, namely a group of hypertension patients having a systolic blood pressure higher than 150 mm Hg and a diastolic blood pressure higher than 90 mm Hg before administration of TR or PR, and a group of non-hypertension patients. The blood pressure was determined after the administration of TR, PR or placebo. The results are shown in Table 2.

Table 2 Medicine Before or Hypertension Group Non-Hypertension Group Afteradmi- Number Systolic Diastofic Number Systolic Diastolic nistration ofcase Pressure Pressure Of Cases Pressure Pressure (mmHg) (mmHg) (mmHg) (mmHg) before 164i.7 96i0.7 128+1.1 75+0.7 TR 80 130 after 152+1.9 86+0.9 131+3.8 76+0.9 before 168+3.4 92+1.2 130+2.4 77to1.5 PR 13 22 after 157t6.9 85+2.4 128+3.8 76t1.8 before 157t1.3 95+2.2 125+2.4 74+1.5 Placebo 20 45 after 151+3.4 90+3.4 131t2.8 76+1.5 From the above results, it is seen that TR has a higher hypotensive activity than PR which is Known to have a hypotensive activity. Further, the hypotensive effect of TR is prominent especially in the hypertension group with respect to the diastolic pressure. Moreover, TR has no effect on the non-hypertension group in which reduction of the blood pressure is unnecessary. Accordingly, TR fully attains the object of providing a remedy for hypertension. Thus, TR is a medicine of value which, when actually applied, shows a high clinical effect, being safe to use.

Test Example 5 - Confirmation of Serum Cholesterol-Reducing Effect in Rabbits Twenty eight rabbits having a body weight of 2.5 to 3 Kg were divided into 4 groups, each consisting of 7 rabbits, so that the average serum cholesterol levels were made substantially equal among these groups.

Standard pellet chow (RC-4, Nippon Clea Co. Ltd.) was given to the first group, and a high-cholesterol diet prepared by adding 1 % of cholesterol to the standard pellet chow (Nippon Clea Co. Ltd.) was given to the second to the fourth groups. The first and second groups were control groups to which no medicine was administered. To the third group, TR orally administered at a dosage of 30 mg/Kg once a day and to the fourth group, TR was orally administered at a dosage of 60 mg/Kg once a day. The serum cholesterol level of each rabbit was measured before the experiment and at two-week intervals during a period of 12 weeks from the start of the experiment. The results are shown in Figure 4.

As shown in Figure 4, the serum cholesterol level is conspicuously increased in the second group which was given the cholesterol diet (line B in the drawing) over the serum cholesterol level in the first group which was given the standard pellet chow (line A in the drawing). By contrast, in the TR-administered third group (line C in the drawing) and fourth group (line Din the drawing), increases in the serum cholesterol levels are apparently controlled. The effect is especially prominent in the fourth group to which TR was administered at a daily dosage of 60 mg/Kg.

Test Example 6 - Comfirmation of Serum Cholesterol-Reducing Effect in Monkeys Twelve healthy Japanese monkeys (male and female) having a body weight of 5.0 to 7.5 Kg were preliminarily bred for 2 months and were divided into 4 groups, each consisting of 3 monkeys. The first group was a control group, and the second to fourth groups were TR-administered groups. To the second group, 30 mg/Kg/day of TR, to the third group, 60 mg/Kg/day of TR, and to the fourth group, 120 mg/Kg/day of TR were orally administered in two equally divided doses.

The serum cholesterol level of each monkey was determined before the experiment and on the 15th and 30th days from the start of the experiment.

To each monkey were given 100 g of a standard laboratory chow (CF-1, Nippon Clea Co. Ltd.) and 300 g of orange per day. The monkeys were allowed tap water ad libitum.

The results are shown in Figure 5.

In Figures, lines E, F, G and H represent the serum cholesterol levels of the first group (control), the second group (30 mg/Kg), the third group (60 mg/Kg) and the fourth group (120 mg/Kg), respectively. As shown in Figure 5, it will readly be understood that the serum cholesterol level decreases by increasing the dose of TR.

Test Example 7 - Confirmation of Serum Cholesterol-Reducing Effect in Humans I TR was orally administered to ischemic heart disease patients with a serum cholesterol level of higher than 250 mg/dl at a dosage of 100 mg X 3 times/day for 4 or 8 weeks. The serum cholesterol level after the administration of TR was examined. The results are shown in Table 3.

Table 3 Experimental Number Administ- Serum Cholesterol Serum Cholesterol Reduction Facility of cases ration Level {mgidl) be- Level (mg/dl) after Ratio period foreAdministra- Administration of TR (%) (weeks) tion of TR A 3 4 291 +24.3 2407.0 16.2+7.3 B 4 4 330+33.2 266+13.4 17.4+7.1 C 3 8 278+11.2 258+13.9 6.6+7.2 D 5 4 284i8.9 224t9.9 20.7+4.2 E 4 4 305+28.9 270i40.5 12.2+6.7 Test Example 8 - Confirmation of Serum Cholesterol-Reducing Effect in Humans II Ischemic heart disease patients having a serum cholesterol level of higher than 200 mg/dl were divided into two groups. To one group, TR was orally administered for 2 weeks followed by the oral administration of a placebo for 2 weeks. To another group, placebo was orally administered for 2 weeks followed by the oral administration of TR for 2 weeks. Each dosage of TR and placebo was 100 mg X 3 times/day.

The serum cholesterol level of each patient was determined before and after the administration of the medicines.

The results are shown in Table 4 and Figure 6.

Table 4 BeforeAdmini- After Administration of TR After Administration of Placebo stration Serum Choles- Serum Chole- Reduction Serum Chole- Reduction terol Level sterol Level Ratio sterol Level Ratio (O/ol (mgidl) {mgidl) (mgldll Group 2237.7 212t9.0 4.9+2.6 225+8.6 -7.1i4.3 1(10 cases) BeforeAdmini- After Administration of Placebo AfterAdministration of TR stration Serum Choles- Serum Chole- Reduction Serum Chole- Reduction terol Level sterol Level Ratio {%) sterol Level Ratio {%) (mg/dl) rmgidl) (mgidl) Group 235t10.8 239+11.8 -1.1+3.4 211.0+15.1 11.7+4.2 2(12 cases) In Figure 6, the solid line shows the serum cholesterol level during the administration of placebo and the broken line shows the serum cholesterol level during the administration of TR. Curve X shows the change in the serum cholesterol level in the group 1 and curve Y shows the change in the serum cholesterol level in the group 2.

As shown in Tables 3 and 4 and Figure 6, it is seen that TR has a definite serum cholesterol-reducing activity and its effect is comparable or superior to the effect of clofibrate (CL), of which the cholesterol reduction ratio was reported to be 6 to 13 % [S. Naito et al., Progress of Medical Science, 102,638(1977)].

The clinical dosage of TR is 1/2 to 1/5 of that of CL. Further, CL often shows relatively serious side effects such as stomach and intestinal disorders (5 - 7 %) and liver disorders (2 - 3 %), whereas the side effects of TR are not so serious. With TR, slight disorders of the digestive organs (1 - 2 %) and a slight headache (1 - 2 %) were reported. Thus, it has been confirmed that TR is excellent also as a serum cholesterol-reducing agent.

Test Example 9-Activity Inhibiting Edematous Reaction in Artery The edematous reaction in artery of rabbits (increase of nuclear indentations of aortic endothelium, contraction of endothelium cells, formation of blisters, edematous swelling of the subendothelial and medial layer, etc.) caused by the oral administration of cholesterol or intraveneous injection of angiotensin II or bradykinin is very similar to the initial lesion of arteriosclerosis in humans. And, it is known that this reaction is inhibited or controlled by pyridino carbamate (PC), which is well known as a remedy for arteriosclerosis [T.

Shimamoto and T. Sunaga, Proc. Japan Acad., 48633 (1972)]. Accordingly, whether or not TR could inhibit or control this edematous reaction in artery caused by the oral administration of cholesterol was examined.

According to the method of Shimamoto etal. [T. Shimamoto and T. Sunaga, Proc. Japan Acad., 48, 633 (1972)], 1 g/Kg of cholesterol was orally administered to the rabbits which had not been fed for 24 hours. Two hours later, the thoracic aorta was removed and embedded in epoxy resin. Then, specimens for an optical microscope and an electron microscope were prepared and subjected to the histopathological observation.

A dose of 6 mg/Kg of TR was orally administered one hour before the administration of cholesterol.

Upon observation under an optical microscope, edematous swelling of medial layer and subendothelial layer of the artery were found in the group to which cholesterol alone was administered (see Figure 7), but such edematous swelling was not observed, or was very slight even if it was observed in the group to which 6 mg/Kg of TR had been orally administered before the administration of cholesterol (see Figure 8).

Upon observation under an electron microscope, contraction of the endothelium cell, nuclei formation of blister and edematous swelling deformation of the subendothelial layer were found in the group to which cholesterol alone was administered (see Figure 9), but in the group to which TR had been administered in advance, such changes were not found at all or very slight if found (see Figure 10).

The endothelium cell nuclei are damaged by the administration of cholesterol, thus inducing certain deformations. As such deformations, there can be mentioned, in the order of lesser severity, notches (indentations with converging sides), folds (indentations with parallel sides), closing fold (indentations with a constriction at the mouth in the manner of a bottleneck) and pinches (folds pressed together so tightly that opposing faces of the outer nuclear membrane came in contact) [G. Majno et al., J. Cell Bio 42,647(1969)].

Since it is assumed that such deformation of the endothelium cell nuclei will induce arteriosclerosis, it is expected that a medicine capable of preventing such deformation will prevent the occurence of arteriosclerosis radically. According ly, whether or not TR could prevent such deformation was examined.

The results are shown in Figure 11. Figure 11 shows that in the TR-administered group the occurence of all types of deformations is controlled as compared with that in the group to which cholesterol alone was administered. Thus, it was confirmed that TR is apparently effective in preventing deformation of the endothelium cells. Since this prevei tive effect of TR is deemed to be equivalent to that of PC when it was given orally at a dose of 10 mg/Kg by T. Shimamoto [T. Shimamoto, Arteriosclerosis, 1,29(1973)], it is apparent that TR has a full effect of preventing the occurrence of arteriosclerosis and it is expected that TR will be an effective remedy for casual treatment of arteriosclerosis.

Test Example 10 - Effect of Preventing Aggregation of the Platelets Coronary artery thrombi inducing coronary insufficiency are said to be white thrombi induced by the aggregation of the platelets and the formation of thrombi is noted as a factor necessary for the manifestation of arteriosclerosis. Accordingly, the influence of TR on the aggregation of the platelets was examined.

According to the method of Vargaftig et al. [B.B. Vargaftig and P. Zirinis, Nature New Biol., 244, (1973)], 0.1 ml of physiological saline solution containing TR or PC was added to 1.0 ml of platelet-rich plasma obtained from the arterial blood of a rabbit. One minute later, 0.1 ml of a solution containing 10 ug of arachidonic acid was added to the above solution and the influence of TR or PC on the aggregation of the platelets was examined by an aggrigometer (Elma EEL 169). The results are shown in Figure 12.

PC, a remedy for arteriosclerosis had no substantial inhibiting effect, whereas TR showed about 50 % inhibition at a concentration of 5 x 10-5 g/ml.

In an experiment conducted separately to examine the influences of TR on the aggregation of the platelets by ADP, it was found that TR has a higher inhibiting effect than dipyridamol. Accordingly, it is believed that the platelet aggregation-inhibiting effect of TR contributes to the remedy for arteriosclerosis by preventing the formation ofthrombi.

Test Example 11 - Anti-Kinin Activity T. Shimamoto et al. proposed that the occurence of atherosclerosis called the edematous reaction in artery takes place in the initial stage of arteriosclerosis, and they also recognized that abnormal local formation of kinin still precedes atherosclerosis [T. Shimamoto, Progress of Medical Sience, 51,443 (1964)].

Accordingly, it is considered that inhibition or control of the activity or formation of kinin may result in the inhibition of the occurrence of edematous reaction in artery and in turn, prevent the occurrence of arteriosclerosis. Therefore, the anti-kinin activity of TR was examined.

The ileum of a guinea pig was removed and pieces of the tissue were suspended in Tyrode's solution in a water bath maintained at 36"C and the influences of TR and PC on contraction caused by addition of 10-7 g/ml of bradykinin was examined. The results are shown in Table 5. A part of the contraction curve is shown in Figure 13.

Table 5 Medicine Concentration (g/ml) Percent Inhibition ( /OJ TR 1 x 10-6 4.413.0 1x105 13.7 2.2 3 x 10-5 22.7 5.3 PC 1x10-6 -2.111.3 1x10-8 2.0 ~ 4.2 3 x 10-5 5.4 to 3.7 Although PC, a remedy for arteriosclerosis, has no substantial anti-kinin activity, TR has a significant anti-kinin activity. Accordingly, it is expected that TR can be a remedy for arteriosclerosis having a greater usefulness than PC.

Test Example 12-Acute Toxicity One group of 10 mice (ICR strain) and another group of 10 rats (Donryu strain) were allowed standard laboratory chow (CE-2, Nippon Clea Co. Ltd.) and tap water. TR was administered orally or by intraveneous injection or subcutaneous injection to examine acute toxicity.

LD50 was calculated from the mortality rate for7 days after the administration of TR when orally administered and was calculated from the mortality for 3 days after the administration in the case of intraveneous and subcutaneous injection, according to the method of Litchfield-Wilcoxon. The results are shown in Table 6.

Table 6 OralAdministration Subcutaneous Intraveneous (mglKg) Injection (mglKg) Injection (mglKg) Mice (male) 740 267 101 Mice (female) 710 253 113 Rats (male) 750 162 125 Rats (female) 570 157 113 The side effects caused by TR will be summarized hereinunder. The side effects observed in 336 of clinical examples are as follows: Symptom Number of diagnosis Headache 2 (0.6%) Discomfort in head 1 (0.3 %) Abdominal discomfort 3 (0.9%) Nauseaorvomiting 4 (1.2%) Anorexia 5 (1.5%) Constipation 3 (0.9 %) Vertigo 1 (0.3%) TOTAL 16 (4.8 %) No allergic side effect was observed by the agent.

From the results of the foregoing experiments, it will readily be understood that in addition to the coronary vasodilating activity, therapeutic agent of the present invention has independently various valuable pharmacological activities such as an activity of promoting formation of the collaterals, a hypotensive activity, a cholesterol-reducing activity, an activity of inhibiting edematous reaction in artery, an activity of preventing aggregation of the platelets and an anti-kinin activity. Since the therapeutic agent of the present invention shows not only the effect of curing ischemic heart disease but also the effects of curing arteriosclerosis and hypertension clinically based on the foregoing activities, it is very valuable as a generic remedy for various circulatory diseases.

For example, when the therapeutic agent of the present invention is applied to ischemic heart disease, it exerts not only a symptomatic effect of increasing the coronary blood flow induced by the coronary vasodilation but also effects preventing the occurrence of arteriosclerosis and hypertension and is significant from the view point of causal treatment, by exerting such effects as promotion of the formation of the collaterals, reduction of cholesterol levels, inhibition of edematous reaction in artery and prevention of aggregation of the platelets. Accordingly, the therapeutic agent of the present invention is extremely useful.

Further, when the therapeutic agent of the present invention is applied to arteriosclerosis, it also shows effects of reducing the serum cholesterol, inhibiting edematous reaction in artery and preventing aggregation of the platelets and an effect of curing hypertension which would otherwise aggravate the state of arteriosclerosis. Accordingly, the therapeutic agent of the present invention is more effective and has a higher usefulness than the conventional agents which mainly show only an effect of improving the lipid metabolism.

When the therapeutic agent of the present invention is applied to hypertension, it shows a prominent effect of reducing the diastolic pressure and no influence on normal blood pressure. Accordingly, no abnormal reduction in blood pressure is brought about, and the therapeutic agent of the present invention is very safe and has a high clinical usefulness.

As shown in the foregoing illustration, the therapeutic agent of the present invention has a great number of independent pharmacological activities in the blood circulatory system. The administration of only the single therapeutic agent of the present invention makes it possible to cure circulatory diseases which are related to one another in a complicated manner so that some of them are risk factors of other diseases and vice versa. Therefore, when the therapeutic agent of the present invention is used as a remedy for circulatory diseases, combined use of medicines can be avoided and patients are set free from complicated side effects caused by the administration of plural medicines.

Moreover, the clinical dosage of the therapeutic agent of the present invention is relatively small and there is almost no manifestation of side effects. Therefore, even if it is administered continuously for a long period of time, it is possible to avoid the occurrence of side effects, such as disorders in the digestive organs and liver caused by clofibrate and hypopotassium and an increase in the uric acid level in the blood, caused by hypotensive diuretics of the thiazide type.

When the therapeutic agent of the present invention is used clinically, it can be advantageously formed into tablets or capsules according to customary methods. More specifically, the therapeutic agent of the present invention can be formed into tablets or capsules by using an excipient such as lactose, starch or mannitol, a disintegrating agent such as carboxymethyl cellulose or potato starch, a binder such as potato starch or gum arabic and a lubricant such as magnesium stearate, talc or silica or it is dissolved into water for injection to yield an injection by ordinary process. Tablets can be sugar-coated according to a customary method.

Although it is preferable that the clinical dosage of the therapeutic agent of the present invention is usually 300 mg/day, said dosage can be increased or decreased depending on the symptom. Furthermore, the present agent can be used in combination with other drugs.

The preparation of medicines by using the therapeutic agent of the present invention will now be described with reference to the following Examples that by no means limit the scope of the invention.

Working Example 1-Tablets (1) TR 50 g (2) Lactose appropriate amount (3) Microcrystalline cellulose 60 g (4) Potato starch 549 (5) Magnesiumstearate 2g The components (1) to (4) are mixed together, and a portion of the component (4) preliminarily separated is added to the mixture in the form of a 10 % starch slurry to form granules. The granules are dried and the powder which has not been formed into granules is removed through a shieve. The component (5) is added to the granules and the mixture is formed into tablets, each containing 200 mg of TR, by using a tableting machine. The formed tablets may be sugar-coated if required.

Working Example 2 - Capsules (1) TR 50g (2) Calcium phosphate, dibasic 50 g (3) Aluminium silicate appropriate amount (4) Microcrystalline cellulose 60g (5) Magnesium stearate 2 9 The components (1) to (5) are mixed together, and the mixture is passed through a sieve and sufficiently biended. Then, according to a customary method, the mixture is formed into capsules, each containing 200 mg of TR.

Working Example 3-Injections After 100 g of crystalline TR is dissolved into 2 liter of water for injection, amples of 100 mg/2 ml of said solution are prepared in accordance with the customary method for producing an injection.

Claims (8)

1. A pharmaceutical composition for the promotion of coronary collaterals in a mammal, comprising as active principal 5-methyl-7-diethylamino-S-triazole (1, 5-a)-pyrimidine and a pharmaceutically acceptable carrier or diluent therefor.

2. A Dharmaceutical composition for lowering of blood pressure in a mammal which comprises as active principal 5-methyl-7-diethylamino-S-triazolo (1 ,5-a)-pyrimidine and a pharmaceutically acceptable carrier or diluent therefor.

3. A pharmaceutical composition for the lowering of serum cholesterol in a mammal comprising as active principal 5-methyl-7-diethylamino-S-triazolo (1,5-a)-pyrimidine and a pharmaceutically acceptable carrier or diluent therefor.

4. A pharmaceutical composition for inhibiting the edamatous reaction in the arteries of a mammal which comprises as active principal 5-methyl-7-diethylamino-S-triazolo (1,5-a)-pyrimidine and a pharmaceutically acceptable carrier or diluent therefor.

5. A composition according to any one of the preceding claims in unit dosage form.

6. A composition according to claim 5 wherein each unit dose contains 200 mg of the active principal.

7. A composition according to claim 5 or claim 6 wherein each unit dosage is in the form of a tablet, capsule or injectable solution.

8. A composition substantially as hereinbefore set forth with reference to and as illustrated in the accompanying drawings and examples.