A stable pharmaceutical mercury-free aqueous solution of cyanocobalamin comprised of cyanocobalamin and water wherein said solution of cyanocobalamin is suitable for intranasal administration, has a viscosity less than about 1000 cPs, and wherein said solution of cyanocobalamin has a bioavailability of cyanocobalamin when administered intranasally of at least about 7% relative to an intramuscular injection of cyanocobalamin with the proviso that the solution is essentially free of mercury and mercury-containing compounds. The present invention is also directed towards a method for elevating the vitamin B12 levels in the cerebral spinal fluid (CSF) comprising administering intranasally a sufficient amount of a mercury-free cyanocobalamin solution so as to increase the average ratio of vitamin B12 in the CSF to that in the blood serum (B12 CSF/B12 Serum.times.100) to at least about 1.1 comprising intranasally administering an aqueous solution of a cyanocobalamin, wherein said solution of cyanocobalamin has a bioavailability of at least 7% relative to an intramuscular injection of a cyanocobalamin.

BACKGROUND OF THE INVENTION

Vitamin B12 is a dietary essential, a deficiency of which results in defective synthesis of DNA in any cell in which chromosomal replication and division are taking place. Since tissues with the greatest rate of cell turnover show the most dramatic changes, the hematopoietic system is especially sensitive to vitamin B12 deficiencies. An early sign of B12 deficiency is a megaloblastic anemia. Dietary B12, in the presence of gastric acid and pancreatic proteases, is released from food and salivary binding protein and bound to gastric intrinsic factor. When the vitamin B12-intrinsic factor complex reaches the ileum, it interacts with a receptor on the mucosal cell surface and is actively transported into circulation. Adequate intrinsic factor, bile and sodium bicarbonate (suitable pH) all are required for ileal transport of vitamin B12. Vitamin B12 deficiency in adults is rarely the result of a deficient diet; rather, it usually reflects a defect in one or another aspect of this complex sequence of absorption. Achlorhydria and decreased secretion of intrinsic factor by parietal cells secondary to gastric atrophy or gastric surgery is a common cause of vitamin B12 deficiency in adults. Antibodies to parietal cells or intrinsic factor complex also can play a prominent role in producing deficiency. A number of intestinal diseases can interfere with absorption. Vitamin B12 malabsorption is seen with pancreatic disorders (loss of pancreatic protease secretion), bacterial overgrowth, intestinal parasites, sprue, and localized damage to ileal mucosal cells by disease or as a result of surgery. The recommended daily intake of vitamin B12 in adults is 2.4 .mu.g.

There are four main forms of vitamin B.sub.12: cyanocobalamin: hydroxocobalamin, methylcobalamin and adenosylcobalamin. Methylcobalamin and adenosylcobalamin are unstable and damaged by light. They are therefore unsuitable for use in dietary supplements or pharmaceuticals and are not essential since they can be formed from cyanocobalamin or hydroxocobalamin within the body. The main form of vitamin B.sub.12 found in food is hydroxocobalamin. The main form used therapeutically and in nutritional supplements is cyanocobalamin, chosen because it is the most stable form and therefore easiest to synthesize and formulate.

Because deficiencies of vitamin B12 are generally caused by the inability of the vitamin to be absorbed in the small intestine due to a breakdown in the vitamin B12-intrinsic factor complex transport mechanism, vitamin B12 must therefore be administered systemically. Currently, therapeutic amounts of cyanocobalamin are administered by intramuscular or deep subcutaneous injection of cyanocobalamin. However, patients must return to the physician's office periodically to receive additional injections to maintain their levels of vitamin B12. However, an intranasal gel cyanocobalamin preparation, NASCOBAL.RTM. is currently being marketed in which cyanocobalamin is administered intranasally as maintenance vitamin B12 therapy. However, many patients find the consistency of the intranasal gel unpleasant and would prefer to have administered intranasally a low viscosity spray containing cyanocobalamin.

The prior art suggests that for vitamin B12 to be absorbed intranasally in therapeutically beneficial amounts, the concentration of the B12 in solution must either be greater that 1% by weight, see Merkus, U.S. Pat. No. 5,801,161 or be administered intranasally in a viscous gel, Wenig, U.S. Pat. No. 4,724,231 so that the gel remains in the nostril for an extended period of time. In fact Wenig states that B12 administered intranasally in a low viscosity solution is not in contact with the nasal mucosa long enough for a sufficient period of time to permit useful absorption. Wenig claims that most of the B12 is wasted if the solution has a low viscosity. Merkus developed intranasal formulations of hydroxocobalamin having a concentration of hydroxocobalamin greater than 1%, however hydroxocobalamin is not very stable and thus has a short shelve-life. Merkus chose hydroxocobalamin because cyanocobalamin is not soluble in an aqueous solution at concentrations greater than 1%.

U.S. Pat. No. 4,525,341, Deihl, discloses a method of administering vitamins intranasally but do not enable a specific formulation containing only cyanocobalamin. International Patent Application No. PCT/US86/00665, publication no. WO 86/05987, and European Patent Application No. EP0218679B1, discloses nasal spray composition containing vitamin B.sub.12 as cyanocobalamin. However, the specific spray formulations all contained a mercury compound as a preservative, however the disclosure did require the presence of mercury compounds. Other preservatives were also mentioned including benzalkonium chloride and chlorobutanol. As was stated above, an intranasal gel containing cyanocobalamin, NASCOBAL.RTM., is currently being produced and marketed by Nastech Pharmaceutical Company Inc. of Bothell, Wash. It is very effective in maintaining levels of vitamin B12 for patients who have been deficient in the past but have recovered their levels of B12 through intramuscular injections. However, a number of patients find the consistency of the gel unpleasant in their nose, and would prefer an intranasal formulation that has a lower viscosity and is free of mercury compounds. Thus, there is a need to produce a pharmaceutically stable aqueous solution of cyanocobalamin that has a low viscosity, is free of mercury compounds and has sufficient bioavailability to be used as a maintenance therapy for vitamin B12.

SUMMARY OF THE INVENTION

The present invention fills this need by providing for a stable pharmaceutical solution of cyanocobalamin suitable for intranasal administration, having a viscosity less than about 1000 cPs, wherein said intranasal solution of cyanocobalamin has a bioavailability of at least 7% of the bioavailability of an intramuscular injection of cyanocobalamin and is free of mercury compounds.

A preferred formulation is comprised of cyanocobalamin, citric acid, sodium citrate, and water wherein the viscosity is less than 1000 cPs, and wherein the solution of cyanocobalamin has a bioavailability of at least 8%, more preferably at least about 9, 10, 11, or 12% of the bioavailability of an intramuscular injection of cyanocobalamin.

Preferred compositions within the scope of this invention will contain a humectant to inhibit drying of the mucous membranes and to prevent irritation. Any of a variety of humectants can be used including but not limited to sorbitol, propylene glycol or glycerol. A preferred humectant is glycerin.

A preservative is generally employed to increase the shelf life of the compositions. Examples of preservative include but are not limited to benzyl alcohol, chlorobutanol and benzalkonium chloride. A preferred preservative is benzalkonium chloride. A suitable concentration of the preservative will be from 0.002% to 2.0% based upon the total weight, although there may be appreciable variation depending upon the agent selected.

A most preferred formulation has the concentration of cyanocobalamin at 0.5% (percent of total weight), citric acid 0.12%, sodium citrate 0.32%, glycerin 2.23%, benzalkonium chloride 0.02% and 96.79% water.

Another embodiment of the present invention is a method for administering cyanocobalamin comprised of infusing the nose with an aqueous solution of cyanocobalamin, wherein the solution of cyanocobalamin has a viscosity of less than 1000 cPs, and wherein said solution of cyanocobalamin has a bioavailability of at least about 7% relative to an intramuscular injection of cyanocobalamin. Preferably, the bioavailability is at least 8%, 9%, 11% or 12%.

The present invention is further directed towards a method for elevating the vitamin B12 levels in the cerebral spinal fluid (CSF) comprising intranasally administering a solution of cyanocobalamin so as to increase the average ratio of vitamin B12 in the CSF to that in the blood serum (B12 CSF/B12 Serum.times.100) to at least about 1.1, wherein said solution of cyanocobalamin has a bioavailability of at least 7% relative to an intramuscular injection of cyanocobalamin. In a more preferred embodiment the B12 CSF levels are increased so that the ratio of B12 in the CSF to the levels in the blood serum is at least 1.9.

DETAILED DESCRIPTION OF THE INVENTION

As noted above, the present invention provides improved methods and compositions for intranasal delivery cyanocobalamin to mammalian subjects for treatment or prevention of a variety of diseases, disorders and conditions. Examples of appropriate mammalian subjects for treatment and prophylaxis according to the methods of the invention include, but are not restricted to, humans and non-human primates, livestock species, such as horses, cattle, sheep, and goats, and research and domestic species, including dogs, cats, mice, rats, guinea pigs, and rabbits.

An initial therapy, the patient should receive daily intramuscular injections of 100 .mu.g of cyanocobalamin for about 1 to 2 weeks, together with 1 to 5 mg of folic acid. Intramuscular injections of cyanocobalamin should not be greater than 100 .mu.g as doses in excess of 100 .mu.g are rapidly cleared from the plasma into the urine, and administration of larger amounts of vitamin B12 will not result in greater retention of larger amounts of the vitamin.

The cyanocobalamin nasal spray of the present invention is directed towards the maintenance of the hematological status of patients who are in remission following intramuscular vitamin B12 therapy. So instead of a once a month injection of 100 .mu.g of cyanocobalamin, using the cyanocobalamin spray, the patient self-administers a dose of the nasal spray of the present invention containing 500 .mu.g of cyanocobalamin once or twice a week. The maintenance therapy of the intranasal cyanocobalamin is for any patient that had been diagnosed with a vitamin B12 deficiency, but especially for those treated for pernicious anemia and dietary deficiency of vitamin B12 occurring in strict vegetarians, the so-called vegans who eat no animal products. Maintenance cyanocobalamin therapy using the cyanocobalamin solution of the present invention is also indicated for those afflicted with malabsorption of vitamin B12 resulting from structural or functional damage to the stomach, where intrinsic factor is secreted or to the ileum, where intrinsic factor facilitates B12 absorption. These conditions include tropical sprue and nontropical sprue (Idiopathic steatorrhea, gluten-induced enteropathy).

Maintenance cyanocobalamin therapy using the cyanocobalamin solution of the present invention is also indicated for those afflicted with malabsorption of vitamin B12 resulting from inadequate secretion of intrinsic factor, resulting from lesion that destroys the gastric mucosa (ingestion of corrosives, extensive neoplasia), and a number of conditions associated with a variable degree of gastric atrophy (such as multiple sclerosis, human immunodeficiency viral (HIV) infection certain endocrine disorders, iron deficiency, and subtotal gastrectomy). Structural lesions that lead to B12 deficiency include ileitis, ileal resections, Crohn's disease and malignancies. Vitamin B12 deficiencies may also be the result of competition by intestinal parasites, and inadequate utilization of vitamin B12 occurring if antimetabolites for the vitamin are employed in the treatment of neoplasia.

The intranasal cyanocobalamin solution of the present invention can also be used for individual who require above normal levels of vitamin B12, due to for example pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, hepatic and renal disease.

As was stated above, the present invention provides for a stable pharmaceutical solution of cyanocobalamin suitable for intranasal administration, having a viscosity less than about 1000 cPs, wherein said intranasal solution of cyanocobalamin has when administered intranasally a bioavailability of at least 7% of the bioavailability of an intramuscular injection of cyanocobalamin. The intranasal formulation will generally be comprised of in addition to water and cyanocobalamin, a buffering agent to maintain the pH between 4 and 6 preferably about 5, a humectanct to inhibit drying of the mucous membranes and a preservative.

A preferred formulation is comprised of cyanocobalamin, citric acid, sodium citrate, and water wherein the viscosity is less than 1000 cPs, and wherein the solution of cyanocobalamin has a bioavailability of at least 7%, more preferably at least about 8, 9, 10, 11, 12% or more of the bioavailability of an intramuscular injection of cyanocobalamin.

Preferred compositions within the scope of this invention will contain a humectant to inhibit drying of the mucous membranes and to prevent irritation. Any of a variety of humectants can be used including, for example sorbitol, propylene glycol or glycerol. A preferred humectant is glycerin.

A preservative is generally employed to increase the shelf life of the compositions. Examples of preservative include benzyl alcohol, parabens thimerosal, chlorobutanol, benzethonium chloride and benzalkonium chloride. A preferred preservative is benzalkonium chloride. A suitable concentration of the preservative will be from 0.002% to 2% based upon the total weight, although there may be appreciable variation depending upon the agent selected.

A most preferred formulation has the concentration of cyanocobalamin at 0.5% (percent of total weight), citric acid 0.12%, sodium citrate 0.32%, glycerin 2.23%, benzalkonium chloride solution 0.02% and 96.79% water.

Other buffering agent combination include but are not limited to:

Monopotassium phosphate and disodium phosphate,

Potassium biphthalate and sodium hydroxide, and

Sodium acetate and acetic acid.

Another embodiment of the present invention is a method for administering cyanocobalamin comprised of infusing the nose with an aqueous solution of cyanocobalamin, wherein the solution of cyanocobalamin has a viscosity of less than 1000 cPs, and wherein said solution of cyanocobalamin has a bioavailability of at least 7% relative to an intramuscular injection of cyanocobalamin. Preferably the bioavailability is at least about 8, 9, 10, 11, 12% or more of the bioavailability of an intramuscular injection of cyanocobalamin.

The present invention is further directed towards a method for elevating the vitamin B12 levels in the cerebral spinal fluid (CSF) comprising intranasally administering a solution of cyanocobalamin so as to increase the average ratio of vitamin B12 in the CSF to that in the blood serum (B12 CSF/B12 Serum.times.100) to at least about 1.1, wherein said solution of cyanocobalamin has a bioavailability of at least 7% relative to an intramuscular injection of a cyanocobalamin. In a more preferred embodiment the B12 CSF levels are increased so that the ratio of B12 in the CSF to the levels in the blood serum is at least 1.9.

This is a significant embodiment of the present invention because vitamin B12 deficiency can result in irreversible damage to the nervous system. Progressive swelling of myelinated neurons, demyelination, and neuronal cell death are seen in the spinal column and cerebral cortex. This causes a wide range of neurological signs and symptoms, including paresthesias of the hands and feet, diminution of vibration and position senses with resultant unsteadiness, decreased deep tendon reflexes, and, in the later stages, confusion, moodiness, loss of memory, and even a loss of central vision. The patient may exhibit delusions, hallucinations, or even an overt psychosis. Since the neurological damage can be dissociated from the changes in the hematopoietic, vitamin B12 deficiency must be considered as a possibility in elderly patients with dementia and psychiatric disorders, even if they are not anemic. Thus, the embodiment of the present invention directed towards increasing the level of vitamin B12 in the CSF can have tremendous benefit for neurological patients. Thus, intranasal administration of vitamin B12 can be used to treat such diseases as Alzheimer's disease, dementia, and multiple sclerosis.
 

Claim 1 of 31 Claims

1. A stable pharmaceutical aqueous solution of cyanocobalamin comprised of cyanocobalamin and water, a preservative selected from the group consisting of benzyl alcohol, parabens thimerosal, chlorobutanol, benzethonium chloride, and benzalkonium chloride, and combinations thereof, a buffer selected from the group consisting of citric acid, sodium citrate, monopotassium phosphate, disodium phosphate, potassium biphthalate, sodium hydroxide, sodium acetate, acetic acid, and combinations thereof, and a humectant selected from the group consisting of sorbitol, propylene glycol, and glycerin, and combinations thereof, wherein said solution of cyanocobalamin is suitable for intranasal administration, has a viscosity less than about 1000 cPs, and wherein said solution of cyanocobalamin has a bioavailability of cyanocobalamin when administered intranasally of at least about 7% relative to an intramuscular injection of cyanocobalamin with the proviso that the solution contains no mercury or mercury compounds.

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