Inhibition of Platelet Aggregation With Substituted Phenylhydratropic Acid Compounds

This invention relates to the prevention of platelet aggregation or thrombus formation by the addition of a compound of the Formula 1 to the plasma surrounding the platelets.

The compounds of the Formula 1 are old compounds known in the art. The compounds are depicted in the protonated or acid form, however, for the purposes of the instant invention the proton can be replaced by any pharmacologically acceptable cation.

For in vivo applications the compositions of the present invention are presented for administration to humans and animals in unit dosage forms, such as tablets, capsules, pills, powders, granules, sterile parenteral solutions or suspensions, and oral solutions or suspensions, and oil-in-water and water-in-oil emulsions containing suitable quantities of the compound of Formula 1.

For oral administration either solid or fluid unit dosage forms can be prepared. For preparing solid compositions such as tablets, the compound of Formula 1 is mixed with conventional ingredients such as talc, magnesium stearate, dicalcium phosphate, magnesium aluminum silicate, calcium sulfate, starch, lactose, acacia, methylcellulose, and functionally similar materials as pharmaceutical diluents or carriers. Capsules are prepared by mixing the compound with an inert pharmaceutical diluent and filling the mixture into a hard gelatin capsule of appropriate size. Soft gelatin capsules are prepared by machine encapsulation of a slurry of the compound with an acceptable vegetable oil, light liquid petrolatum or other inert oil.

Fluid unit dosage forms for oral administration such as syrups, elixirs, and suspensions can be prepared. The water-soluble forms can be dissolved in an aqueous vehicle together with sugar, aromatic flavoring agents and preservatives to form a syrup. An elixir is prepared by using a hydro-alcoholic (ethanol) vehicle with suitable sweeteners such as sugar and saccharin, together with an aromatic flavoring agent.

Suspensions can be prepared with a syrup vehicle with the aid of a suspending agent such as acacia, tragacanth, methylcellulose and the like.

For parenteral administration, fluid unit dosage forms are prepared utilizing the compound and a sterile vehicle, water being preferred. The compound, depending on the vehicle and concentration used, can be either suspended or dissolved in the vehicle. In preparing solutions the compound can be dissolved in water for injection and filter sterilized before filling into a suitable vial or ampul and sealing. Advantageously, adjuvants such as a local anesthetic, preservative and buffering agents can be dissolved in the vehicle. To enhance the stability, the composition can be frozen after filling into the vial and the water removed under vacuum. The dry lyophilized powder is then sealed in the vial and an accompanying vial of water for injection is supplied to reconstitute the liquid prior to use. Parenteral suspensions are prepared in substantially the same manner except that the compound is suspended in the vehicle instead of being dissolved and sterilization cannot be accomplished by filtration. The compound can be sterilized by exposure to ethylene oxide before suspending in the sterile vehicle. Advantageously, a surfactant or wetting agent is included in the composition to facilitate uniform distribution of the compound.

For in vitro applications, aqueous solutions are prepared by dissolving a compound of the Formula 1 in water and adding salt to provide an isotonic solution and buffering to a pH compatible with blood.

Advantageously the composition prepared for parenteral administration can be used when prepared omitting the local anesthetic.

The dosage for humans and animals depends on the blood volume and condition of the subject. A dosage schedule of from about 0.1 to about 100 mg. per dose administered 1 to 3 times daily is effective for reducing platelet aggregation in the subject. Expressed in terms of weight, the dose can be from 0.001 to 1.5 mg./kg./day. The preferred dose is 1 to 10 mg. orally 1 to 3 times a day for an adult human.

For in vitro, dosage is from 0.01 to 50 micrograms/ml. of whole blood.

The compounds of the Formula 1 having an asymetric carbon atom exists as optical isomers. For the purpose of the instant invention the racemic mixtures and dextro forms are active. The levo forms are inactive.

The compounds of the Formula 1 are depicted in the protonated or acid form, however, for the purposes of the instant invention the proton can be replaced by any pharmacological acceptable anion. These salts are disclosed in Netherlands patent 66,08098 (Derwent No. 24,299) and can be for example those of alkali metals and alkaline earth bases, such as the sodium potassium, calcium and magnesium salts; those of ammonia or a basic amine such as mono-, di-, and triethyl amines, benzylamine, heterocyclic amines such as piperidine and morpholine, and amines containing water-solubilizing or hydrophilic groups such as triethanolamine and phenylmonoethanolamine are disclosed in U.S. Pat. No. 3,296,091. Carboxylate esters such as methyl, ethyl, cyclohexyl and the like having no more than eight carbon atoms are formed by the usual methods, e.g., reaction with diazomethane or similar diazohydrocarbons as in U.S. Pat. No. 3,296,091.

The addition of compounds of the Formula 1 to whole blood provide in vitro applications of the invention such as in the storage of whole blood in blood banks, and whole blood to be used in heart-lung machines. Additionally, whole blood containing a compound of the Formula 1 can be circulated through organs, e.g., heart and kidneys, which have been removed from a cadaver and prior to transplant.

The compounds of the Formula 1 can also be used for the preparation of stable platelet-rich plasma concentrates in the same manner as the prostaglandins as disclosed in U.S. Pat. No. 3,629,071 and Science. Vol. 175, pp. 536-542 (Feb. 4, 1972).

In vivo applications are the administration to humans and animals to prevent clot formation in situations such as following surgery to prevent postoperative thrombosis; in geriatric patients to prevent transient cerebral ischemic attacks; and long-term prophlaxis following myocardial infarcts and strokes.

In general a compound of the Formula 1 is usefully administered prophylactically to humans having a platelet adhesiveness value in excess of 25% [Bygdeman et al., J. Atherosoler, Res., 10, 33-39 (1969)].

Following a single oral 10 mg. dose of 3-fluoro-4-phenylhydratropic acid, collagen-induced platelet aggregation was inhibited in human volunteers. Chronic administration of 10 mg. every eight hours for a total of 22 doses also inhibited aggregation to a similar degree.

Twelve healthy male volunteers were used for this study. These subjects had no previous history of ulcer disease, hepatitis, aspirin sensitivity or a bleeding disorder. They ranged in age from 21 to 55 and weighed no more than 180 pounds. They were not receiving chronic concurrent medication and had no abnormal ECG or chest X-ray. Furthermore, they did not smoke during the course of the study.

The twelve volunteers were randomly divided into two groups of six and 15 ml. blood samples taken before, one hour after the first 10 mg. dose of 3-fluoro-4-phenylhydratropic acid (or placebo) and one hour after the 22nd dose of 10 mg. every eight hours of 3-fluoro-4-phenylhydratropic acid (or placebo).

The blood was anticoagulated with sodium citrate (1 part 3.8% sodium citrate to 9 parts blood) and centrifuged in 5 ml. aliquots at 1,000 RPM for 10 minutes (International Centrifuge, size 2). The platelet-rich plasma (PRP) was removed with a glass pipette and the remaining blood was centrifuged at 3,000 RPM for 15 minutes. Platelet-poor plasma (PPP) was pipetted off and the red cells discarded. All glassware used to this point was siliconized with SC-87 (GE) (5% in tetrahydrofuran).

Platelet counts were adjusted with PPP from corresponding samples to 250,000/mm (Coulter Counter, Model B).

Platelet aggregation was measured on a Payton Aggregation Module (Payton Assoc., Buffalo, N.Y.). To 0.95 ml. of PRP warmed to 37.degree. C., 0.05 ml. of a collagen suspension was added and stirred. The extent of recorder pen deflection was used as an index of platelet aggregation.

The collagen suspension was prepared as previously described [Hovig, T. Thromo, Diathes. Haemorrh. (Stuttg). 9: 248 (1963)] and diluted with Tyrode's solution to give less than maximal aggregation.

Table 1 shows that there was a significant inhibitory effect on collagen-induced platelet aggregation following the oral administration of 3-fluoro-4-phenylhydratropic acid. This effect was evident even after a single dose of 10 mg.

Human blood (1 part 3.8% citrate to 9 parts blood) was obtained from volunteers via a vein in the forearm.

Rat blood (1 part 2.2% citrate to 9 parts blood) was obtained from anesthetized (cyclopal) animals via the abdominal acrta.

Rabbits were anesthetized with pentobarbital and a carotid artery cannulated. After the animal had recovered from anesthesia, 10 ml. of blood (1 part 3.8% citrate to 9 parts blood) was drawn. They were then orally dosed with 3-fluoro-4-phenylhydratropic acid or saline and a second sample was drawn 1.5 hrs. later.

All platelet counts were made with a Coulter Counter, Model B (Coulter Electronics, Hialeah, Fla.). Rat platelet count was adjusted to 500,000/mm. Rabbit platelet counts were equalized with platelet poor plasma (PPP) from corresponding blood samples.

Aggregation was measured as previously described in Example 1 with a collagen (Sigma, St. Louis, Mo.) suspension as the aggregating stimulus.

A lot of 10,000 tablets, each containing 0.1 mg. of 3-fluoro-4-phenyl-hydratropic acid is prepared from the following types and amounts of ingredients:

The dicalcium phosphate is mixed well, granulated with 7.5 percent solution of methylcellulose in water, passed through a No. 8 screen and dried carefully. The dried granules are passed through a No. 12 screen, mixed thoroughly with the talc, starch and magnesium stearate, and compressed into tablets.

These tablets are useful in preventing thrombus formation at a dose of 1 tablet every four hours following surgery.

One thousand two-piece hard gelatin capsules, each containing 100 mg. of 3-fluoro-4-phenyl-hydratropic acid are prepared from the following types and amounts of ingredients:

The ingredients are mixed well and filled into capsules of the proper size.

Capsules so prepared are useful in preventing further coronary infarcts at a dose of 1 capsule daily to a patient recovering from a coronary infarct.

One thousand tablets, each containing 100 mg. of 3-fluoro-4-phenyl-hydratropic acid are made from the following types and amounts of ingredients:

The ingredients are screened and blended together and pressed into 240 mg. tablets.

The tablets are useful to protect against transient cerebral ischemic attacks at a dose of 1 tablet daily.

A sterile preparation suitable for intramuscular injection and containing 1 mg. of 3-fluoro-4-phenyl-hydratropic acid in each milliliter is prepared from the following ingredients:

One milliliter of this sterile preparation is injected for prophylactic treatment prior to surgery.

Six hundred ml. of an aqueous solution containing 0.1 mg. of the tris(hydroxymethyl)aminomethane (THAM) salt of 3-fluoro-4-phenyl-hydratropic acid per ml. is prepared as follows:

The THAM salt and sodium chloride are dissolved in sufficient water to make 600 ml. and sterile filtered.

The solution is added to whole blood 16.0 ml./liter for use in a heart-lung machine.

Following the procedure of the preceding examples 1 through 7 inclusive, compositions are similarly prepared substituting an equimolar amount each of 3-chloro-4-cyclohexyl-hydratropic acid and 3-bromo-4-phenyl-hydratropic acid for the 3-fluoro-4-phenyl-hydratropic acid of the previous examples.