FIELD OF THE INVENTION
The present invention relates to gastric retention systems and to pharmaceutical dosage forms that use them to release a drug in a patient's stomach or duodenum. More particularly, the invention relates to gastric retention systems suitable for use with bis-phosphonates such as alendronic acid and its pharmaceutically acceptable salts and hydrates thereof to release these drugs in a controlled manner.
BACKGROUND OF THE INVENTION
After discovery of a new drug for treatment of a human disease further investigation must be undertaken to determine whether it is most effective to administer the drug to a patient intravenously, transdermally, subcutaneously or orally. Orally administered drugs are easy to administer and therefore are often favored whenever an oral route is feasible. However, compliance problems sometimes occur with orally administered drugs when the dosage form is inconvenient to take or must be taken frequently or at inconvenient times. Orally administered drugs are often presented to a patient in such dosage forms as tablets, pills, lozenges and capsules. Most orally administered drugs are absorbed into the bloodstream from the patient's gastrointestinal tract, excepting inhalants which are absorbed by the lungs and sinuses.
Orally-administered drugs may be absorbed more readily by the gastrointestinal (“GI”) tract through either the stomach wall or the intestine wall. Few drugs are efficiently absorbed by the colon. Tablets that are designed to carry drugs that are more readily absorbed through the intestine wall are sometimes covered with a coating that is resistant to the acidic conditions of the stomach but which decomposes under the basic conditions of the intestine. This enteric coating allows the tablet to transit the stomach without releasing the active ingredient until it reaches the portion of the GI tract where it is most readily absorbed. This enteric-coating strategy is also effective when the drug is caustic to the lining of the stomach or decomposes under acidic conditions.
It is sometimes desirable that a drug be released in a patient's stomach rather than in the intestine. One such instance is when it is therapeutically advantageous to release the drug over several hours. The average residence time of solid food in the small intestine is about three hours. A controlled release pharmaceutical dosage form may pass through the stomach and intestine and into the colon before the active ingredient has been completely released. However, if the dosage form is retained in the stomach, complete release occurs upstream of the small intestine and the active ingredient will enter the intestine in an unbound state in which it can be readily absorbed before reaching the colon.
It is also desirable to release a drug in the stomach when it is unstable to the basic conditions of the intestine. A composition that is formulated to dissolve upon contact with any aqueous solution will at least partially dissolve in the stomach because it reaches the stomach before it reaches the intestine. However, the average residence time of food in the stomach is only about 1 to 3 hours. Unless the drug is very rapidly absorbed, or the residence time is increased, some of the drug will pass to the intestine. An unstable drug will at least partially decompose to a product compound that either is not absorbed or, if absorbed, may not exert the desired therapeutic effect. Accordingly, decomposition of a base sensitive drug that passes into the intestine reduces the effectiveness of the dosage and, as well, introduces an uncontrollable factor that is detrimental to accurate dosing.
For the foregoing reasons, formulation chemists have developed strategies to increase the retention time of oral dosages in the stomach. One of the general strategies, involves using an intragastric expanding dosage form that swells upon contact with stomach juices, preventing its passage through the pylorus. Intragastric expanding dosage forms use hydrogels which expand upon contact with water to expand the dosage form to sufficient size to prevent its passage through the pylorus. An example of such a dosage form is described in U.S. Pat. No. 4,434,153. The '153 patent discloses a device for executing a therapeutic program after oral ingestion, the device having a matrix formed of a non-hydrated hydrogel and a plurality of tiny pills containing a drug dispersed throughout the matrix.
As reviewed by Hwang, S. et al. “Gastric Retentive Drug-Delivery Systems,” Critical Reviews in Therapeutic Drug Carrier Systems, 1998, 15, 243-284, one of the major problems with intragastric expanding hydrogels is that it can take several hours for the hydrogel to become fully hydrated and to swell to sufficient size to obstruct passage through the pylorus. Since food remains in the stomach on average from about 1 to 3 hours, there is a high probability that known expanding dosage forms like that of the '153 patent will pass through the pylorus before attaining a sufficient size to obstruct passage.
The rate-limiting factor in the expansion of ordinary hydrogels is the rate of delivery of water to non-surfacial hydrogel material in the dosage form. Conventional non-hydrated hydrogels are not very porous when dry and ingress of water into the hydrogel is slowed further by the formation of a low permeability gelatinous layer on the surface after initial contact with water. One approach to solving this problem uses so-called superporous hydrogels. Superporous hydrogels have networks of pores of 100 μ diameter or more. Pores of that diameter are capable of efficient water transport by capillary action. Water reaches the non-surfacial hydrogel material quickly resulting in a rapid expansion of the superporous hydrogel to its full extent. However, there are also shortcomings attendant to the use of superporous hydrogels. They tend to be structurally weak and some are unable to withstand the mechanical stresses of the natural contractions that propel food out of the stomach and into the intestine. The superporous hydrogels tend to break up into particles too small to be retained.
Non-superporous hydrogels do not suffer from mechanical strength problems to as great an extent as superporous hydrogels. An additional advantage of using conventional hydrogels is that their degradation/erosion rates are well studied. The blended composition of the present invention should be compared with the superporous hydrogels described in Chen, J. and Park, K. Journal of Controlled Release 2000, 65, 73-82, wherein the mechanical strength of superporous hydrogels is improved by the polymerization of precursor hydrogel monomers in the presence of several superdisintegrants. The result of the polymerization described by Chen and Park is a new substance having interconnecting cross-linking networks of polyacrylate and, e.g. cross-linked carboxymethyl cellulose sodium. Such interconnecting networks are not expected to have the same degradation rates as conventional hydrogels made from the same precursor hydrogel monomers.
Many disease therapies can benefit from improvements in controlled gastric release technology, such as osteoporosis and Paget's disease. Bis-phosphonates such as alendronate, residronate, etidronate and teludronate are commonly prescribed drugs for treatment of these diseases. Despite their benefits, bis-phosphonates suffer from very poor oral bioavailability (Gert, B. J.; Holland, S. D.; Kline, W. F.; Matuszewski, B. K.; Freeman, A.; Quan, H.; Lasseter, K. C.; Mucklow, J. C.; Porras, A. G.; Studies of the oral bioavailablity of alendronate, Clinical Pharmacology & Therapeutics (1995) 58, 288-298), serious interference of absorption by foods and beverages other than water (ibid.), and side effects that consist of irritation of the upper gastrointestinal mucosa (Liberman, U. A.; Hirsch, L. J.; Esophagitis and alendronate, N. Engl. J. Med. (1996) 335, 1069-70) with the potential for this irritation leading to more serious conditions (Physicians' Desk Reference, Fosamax, Warnings).
To overcome these limitations, the bis-phosphonates, such as alendronate, have been given in relatively large doses in a fasting condition while maintaining an upright position for at least a half an hour after dosing (Physicians' Desk Reference, Fosamax, Dosage and Administration). Since bis-phosphonates are not metabolized, dosing also can be lowered to once a week instead of daily (70 mg per dose once a week in place of 10 mg per dose daily) by administering very large sustained-release doses of the drug, (Daifotis, A. G.; Santora II, A. C.; Yates, A. G.; Methods for inhibiting bone resorption, U.S. Pat. No. 5,994,329).
Alendronate is best absorbed from the upper GI tract (duodenum and jejunum) (Lin, J. H.; Bisphosphonates: a review of their pharmacokinetic properties, Bone (1996), 18, 75-85. Porras, A. G.; Holland, S. D.; Gertz, B. J.; Pharmacokinetics of Alendronate, Clin Pharmacokinet (1999) 36, 315-328), and is better absorbed at a pH of ˜6 (Gert, B. J.; Holland, S. D.; Kline, W. F.; Matuszewski, B. K.; Freeman, A.; Quan, H.; Lasseter, K. C.; Mucklow, J. C.; Porras, A. G. ; Studies of the oral bioavailablity of alendronate, Clinical Pharmacology & Therapeutics (1995) 58, 288-298). Only gastric retention with controlled release allows for the extended delivery of a drug to the duodenum. Controlled release of the drug to the duodenum and jejunum parts of the intestine should allow an improvement in bioavailability, thus allowing a lowering of the total dose of the drug.
SUMMARY OF THE INVENTION
We have now found a rapidly expanding oral dosage form that swells rapidly in the gastric juices of a patient, thereby increasing the likelihood that an active ingredient carried by the form will be released in the stomach. This oral dosage form employs a blend of a superdisintegrant, tannic acid and one or more conventional hydrogels. The dosage forms of the present invention swell rapidly, yet because they do not require superporous hydrogels, do not have their associated mechanical strength problems.
The present invention further provides compacted pharmaceutical compositions for oral administration to a patient which expand upon contact with gastric fluid to retain a dosage form in the patient's stomach for an extended period of time, the formulation comprising a blend of a non-hydrated hydrogel, a superdisintegrant and tannic acid.
The present invention further provides a pharmaceutical dosage form containing an active ingredient and the compacted pharmaceutical composition.
Yet further, the present invention provides compositions and dosage forms for delayed release of bis-phosphonates. The dosage forms release the bis-phosphonates into the stomach of a patient suffering from osteoporosis or Paget's disease The dosage forms include a drug delivery vehicle which retains the dosage form in the patient's stomach for an extended period of time. In some embodiments of the invention, the drug delivery vehicle further provides a means to slow the release of the bis-phosphonate. Bis-phosphonate is released into the stomach over at least a portion of the period that the dosage form is retained in the stomach.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a carrier composition for a pharmaceutically active ingredient and dosage forms containing the carrier composition and the active ingredient. Tablets containing the inventive composition swell rapidly on contact with aqueous solution, such as the gastric juices of a patient and simulated gastric fluid. Rapid swelling is achieved by a novel combination of hydrogel, superdisintegrant and tannic acid.
The preferred hydrogel of the present invention is hydroxypropylmethylcellulose, either alone or in combination with hydroxypropyl cellulose and/or a cross-linked acrylate polymer. Suitable cross-linked acrylate polymers include polyacrylic acid crosslinked with allyl sucrose commercially available under the trade name Carbopol® (BF Goodrich Chemical Ltd.) and polyacrylic acid cross linked with divinyl glycol. As further illustrated by Examples 5 and 8, below, a preferred hydrogel of the invention is a mixture of hydroxypropyl methylcellulose and hydroxypropyl cellulose. The most preferred hydrogel of the present invention is a combination of hydroxypropyl methylcellulose and hydroxypropyl cellulose in a weight ratio of from about 1:3 to about 5:3. The molecular weight of the hydrogels is not critical to practice of the invention.
The inventive composition also includes a superdisintegrant. Superdisintegrants are pharmaceutical excipients within a larger class of excipients known as disintegrants. Disintegrants are typically hydrophilic polymers of either natural or synthetic origin. Superdisintegrants are disintegrants that swell upon contact with water. Preferred superdisintegrants of the present invention swell to at least double their non-hydrated volume on contact with water. Exemplary of these superdisintegrants are cross-linked polyvinyl pyrollidone (a.k.a. crospovidone), cross-linked carboxymethyl cellulose sodium (a.k.a. croscarmelose sodium) and sodium starch glycolate. Crospovidone is commercially available from BASF Corp. under the tradename Kollidon® CL and from International Specialty Chemicals Corp. under the tradename Polyplasdone®. Croscarmellose sodium is commercially available from FMC Corp. under the tradename Ac-Di-Sol® and from Avebe Corp. under the tradename Primellose®. Sodium starch glycolate is commercially available from Penwest Pharmaceuticals Co. under the tradename Explotab® and from Avebe Corp. under the tradename Primojel®. The most preferred superdisintegrant is sodium starch glycolate.
The inventive composition further includes tannic acid. Tannic acid, also called tannin, gallotannin and gallotannic acid, is a naturally occurring constituent of the bark and fruit of many trees. The term “tannins” conventionally refers to two groups of compounds, “condensed tannins” and “hydrolyzable tannins.” Merck Index monograph No. 8828 (9th ed. 1976). The hydrolyzable tannins are sugars that are esterified with one or more (polyhydroxylarene) formic acids. One common polyhydroxylarene formic acid is galloyl (i.e. 3,4,5-trihydroxybenzoyl). Another common polyhydroxylarene formic acid substituent of tannins is meta-digallic acid. A common sugar moiety of tannins is glucose. The tannic acid of the present invention is selected from the hydrolyzable tannins, and especially glucose tannins in which one or more of the hydroxyl groups of glucose is esterified with gallic acid and/or meta-digallic acid.
The novel expanding composition of the present invention comprises hydroxypropyl methylcellulose, optionally in combination with other hydrogel polymers, a superdisintegrant and tannic acid. These excipients are preferably combined in a weight ratio, exclusive of any other excipients that may be present, of from about 20 wt. % to about 80 wt. % hydrogel, from about 10 wt. % to about 75 wt. % superdisintegrant and from about 2 wt. % to about 15 wt. % tannic acid. A preferred composition comprises from about 30 wt. % to about 55 wt. % superdisintegrant, about 5 wt. % (±2 wt. %) tannic acid, plus an amount of hydrogel sufficient to bring the total to 100 wt. %.
One especially preferred embodiment of the present invention is a rapidly expanding pharmaceutical composition comprising from about 10 wt. % to about 20 wt. % hydroxypropyl methyl cellulose, from about 45 wt. % to about 50 wt. % hydroxypropyl cellulose, about 25 wt. % to about 35 wt. % sodium starch glycolate and about 4 wt. % to about 6 wt. % tannic acid. A second especially preferred embodiment of the present invention is a rapidly expanding pharmaceutical composition comprising from about 20 wt. % to about 30 wt. % hydroxypropyl methyl cellulose, from about 10 wt. % to about 20 wt. % hydroxypropyl cellulose, about 45 wt. % to about 55 wt. % sodium starch glycolate and about 4 wt. % to about 6 wt. % tannic acid.
The novel composition of the invention can be prepared conventionally by dry blending. In order to form a structurally resilient mass upon contact with water or gastric fluid, the blended composition is compacted prior to hydration.
One object of the invention is to provide a dosage form such as a tablet that is retained in the stomach for an extended period of time by swelling to a size that prevents passage through the pylorus upon contact with gastric juices. Over time the swollen tablet degrades or erodes into particles that are sufficiently small to traverse the pylorus. The tablet may be compacted following conventional dry granulation or direct compression techniques.
The pharmaceutical dosage forms of the present invention comprise the compacted expanding composition of the invention and an active ingredient. Active ingredients that may be carried by these dosage forms include, but are in no way limited to, bis-phosphonates such as alendronic acid and its pharmaceutically acceptable salts and hydrates, levodopa, carbidopa, methylphenidate, diltiazem, irinotecan and etoposide. Preferably, the pharmaceutical dosage forms are retained in the stomach for three hours or more, more preferably about five hours or more. In order to obstruct passage through the pylorus, the dosage form preferably swells by a factor of five or more, more preferably about eight or more, within about fifteen minutes of contacting gastric fluid. Yet more preferably, such swelling is reached within about five minutes.
The novel composition of the invention can be prepared conventionally by dry blending. In order to form a structurally resilient mass upon contact with water or gastric fluid, the blended composition is compacted prior to hydration. The composition may be compacted following conventional dry granulation or direct compression techniques.
For instance, the blended composition may be compacted into a slug or a sheet and then comminuted into compacted granules. The compacted granules may be compressed subsequently into a final dosage form. It will be appreciated that the processes of slugging or roller compaction, followed by comminution and recompression render the hydrogel, superdisintegrant and tannic acid intragranular in the final dosage form. The active ingredient of the pharmaceutical may also be provided intragranularly by blending it with the expanding composition prior to compaction. Alternatively the active ingredient may be added after comminution of the compacted composition, which results in the active ingredient being extragranular.
As an alternative to dry granulation, the blended composition may be compressed directly into the final pharmaceutical dosage form using direct compression techniques. Direct compression produces a more uniform tablet without granules. Thus the active ingredient and any other desired excipients are blended with the composition prior to direct compression tableting. Such additional excipients that are particularly well suited to direct compression tableting include microcrystalline cellulose, spray dried lactose, dicalcium phosphate dihydrate and colloidal silica. An additional alternative to dry granulation is wet granulation. The blend of excipients may be granulated using water or an alcohol as a granulation solvent by standard granulation techniques known in the art followed by drying.
In addition to the above-described excipients, the rapidly expanding pharmaceutical composition and dosage form may further include any other excipients. One factor that must be taken into account in formulating a pharmaceutical composition is the mechanical process which the composition undergoes to be transformed into a dosage form, such as a tablet or capsule. Some excipients are added to facilitate this mechanical processing, such as glidants and tablet lubricants. Glidants improve the flow properties of the composition in powder or granule form while lubricants ease ejection of a tablet from the tableting dye in which it is formed by compression. Silicon dioxide is a common glidant, while magnesium is a common tablet lubricant. Thus, for example, the present inventive composition may further include silicon dioxide and magnesium stearate. Other excipients which may be mentioned are binders, that are added to prevent flaking and other types of physical disintegration of the tablet prior to ingestion by a patient. Yet other excipients are diluents whose presence causes the tablet to be larger and thus easier for a patient to handle.
Further increase in retention times can be realized by the addition of a compound that produces gas when contacted with acid, such as sodium bicarbonate. Sodium bicarbonate may be provided by blending into the expanding composition of the invention or may be an extragranular constituent of a tablet prepared by dry granulation. Sodium bicarbonate is preferably used at low concentration, of from about 0.5 wt % to about 5 wt. % of expanding composition.
In addition to the above-described use of the expanding composition in tablets prepared by dry or wet granulation and compression, there are many other embodiments in which the expanding composition could be used to retain a drug delivery vehicle in the stomach. For instance, the expanding composition can be used to coat a smaller tablet (this is a preferred construction of a gastric retention dosage form of alendronate, described below). The expanding composition can be used advantageously in this way in sustained delivery of a drug. After contact with aqueous fluid and swelling, the composition is highly porous. Thus, the release rate of a sustained release dosage form like a coated tablet or slowly disintegrating tablet is substantially unaffected by a coating of the expanding composition.
The expanding composition is also suited for the retention of drugs in the stomach when such drugs are contained in tablets that are either partially embedded in the expanding composition or attached thereto by an adhesive. These tablets can be of a slow release nature giving slow or controlled release for an extended period of time in the stomach. These tablets can further be of a delayed pulse release nature. The expanding composition of this invention will retain these forms in the stomach until the delay time has passed whereupon the drug will be released in a burst or pulse fashion. Attaching, or partially embedding, several such tablets, each timed with a different relay to release, to the composition of this invention, allows versatile dosing schemes from one taken dose. For example, one could deliver three (or more) timed doses in a pulse fashion while the patient needs to take the dose only once. The three doses would mimic taking three doses of the drug at the prescribed times, with the drug being absorbed from the stomach with each dose. Such dosing allows for improved compliance to dosage schedules and in many cases will lead thereby to improved therapy.
Delayed dosage forms that are not coupled to gastric retention will deliver each such dose in a different part of the GI tract with different absorption profiles for each of the doses. Such therapy would not be equivalent to taking three doses of the drug at the prescribed times, wherein the drug would have been absorbed from the stomach in each case.
The present invention provides a delayed release dosage form containing the delivery vehicle/composition of the invention and a therapeutic bis-phosphonate that is capable of delivering the bis-phosphonate to the stomach of a patient several hours after administration.
Suitable bis-phosphonates include alendronic acid and its pharmaceutically acceptable salts and hydrates thereof, as well as residronate, etidronate and teludronate.
The bis-phosphonate drug delivery vehicle may be formed from the afore-described hydrogel, superdisintegrant and tannic acid by blending or granulating. Regardless of the method by which the hydrogel, superdisintegrant and tannic acid are combined, they are preferably combined in a weight ratio, exclusive of the bis-phosphonate and any other excipients that may be present, of from about 50 wt. % to about 80 wt. % hydrogel, from about 10 wt. % to about 30 wt. % superdisintegrant and from about 5 wt. % to about 15 wt. % tannic acid. A yet more preferred drug delivery vehicle comprises from about 15 wt. % to about 25 wt. % superdisintegrant, about 10 wt. % (±2 wt. %) tannic acid, plus an amount of hydrogel sufficient to bring the total to 100 wt. %. One especially preferred bis-phosphonate delivery vehicle comprises from about 15 wt. % to about 20 wt. % hydroxypropyl methyl cellulose, from about 45 wt. % to about 55 wt. % hydroxypropyl cellulose, about 20 wt. % to about 25 wt. % carboxy methyl cellulose sodium and about 8 wt. % to about 12 wt. % tannic acid.
Dosage forms containing the drug delivery vehicle and bis-phosphonate swell rapidly on contact with aqueous solution, e.g. water, gastric fluid and acidic solutions like simulated gastric fluid. In order to obstruct passage through the pylorus, the drug delivery vehicle preferably swells by a factor of five or more, more preferably about eight or more, within about fifteen minutes of contacting gastric fluid. Yet more preferably, such swelling is reached within about five minutes. Preferably, the swelling causes retention of the pharmaceutical dosage forms in the stomach for three hours or more, more preferably about four hours or more, after which time the drug delivery vehicle either dissolves or degrades into fragments small enough to pass through the pylorus.
The invention further relates to specific pharmaceutical dosage forms containing a therapeutic bis-phosphonate and the drug delivery vehicle. These forms may have (a) a monolithic construction, such as a tablet made by conventional direct compression or granulation techniques wherein the active is dispersed in the drug delivery vehicle, (b) a layered construction wherein the active, alone or in mixture with any other excipients, form a layer that is bonded, e.g. by compression, to another layer formed of the drug delivery vehicle, (c) an encapsulated construction wherein either of the (a) or (b) type constructions are encapsulated, (d) a coated construction wherein a core containing the actives is coated with the drug delivery vehicle, and (e) a construction whereby the drug is incorporated in an optionally coated matrix tablet, said tablet being partially embedded in the drug delivery vehicle, or attached externally to the drug delivery vehicle by an adhesive.
A monolithic dosage form can be prepared by the direct compression and granulation methods previously described. The monolithic dosage form may be made in any shape desired, but it has been found that an ovoid or elliptical shape is advantageous for retaining the dosage form in the stomach. An ovoid or elliptical dosage form preferably is sized at between about 4 mm and 8 mm in two dimensions and between about 10 mm and 20 mm in the third dimension, more preferably about 6×6×16 mm. Monolithic dosage forms slow the release of the actives due to the diffusional barrier created by the surrounding swelled hydrogel. The diffusion may slow to the point that release occurs by erosion of the drug delivery vehicle.
In a monolithic dosage form, delayed release of the actives may be provided by coating the actives with a delay release coating according to methods known to the art. Thus, where the foregoing description of the present invention has described mixing, blending, granulating, compressing, etc. of the actives, it will be appreciated by those skilled in the art that the actives may previously be coated with a coating that erodes slowly in gastric fluid to provide a delay in release of the actives. In particular, a monolithic dosage form may contain microgranules, microcapsules or coated beads containing the actives.
A particularly preferred bis-phosphonate dosage form is a coated construction wherein the drug delivery vehicle coats a core containing the active. This construction is illustrated in detail with Examples 9-12, below. A coated construction delays the release of the active by providing a diffusional barrier through which the active must pass before it is released. As illustrated in the Examples, a coated construction can provide either a delayed/rapid release or a delayed/extended release of the active depending upon the formulation of the core.
A preferred layered construction is one which contains the drug delivery vehicle in one layer and the actives in another layer. Preferred dimensions for this embodiment are about 14×8 mm. A layered construction may be prepared by conventional multilayer compression techniques. A layered dosage form comprising two layers, one comprising the drug delivery vehicle and the other comprising the actives and any other desired excipients, may be made to delay release of the actives by coating only the actives-containing layer with a conventional coating resistant to gastric fluids. A further method of achieving a delay in the release is to formulate the drug containing layer as a matrix that delays diffusion and erosion or by incorporating the active substances in microcapsules or coated beads within the drug containing layer.
The drug delivery vehicle is also suited for the retention of the actives in the stomach when the actives are contained in tablets that are either partially embedded in the drug delivery vehicle or attached thereto by an adhesive. In addition to being of sustained release nature, these tablets can further be of a delayed pulse release nature or a delayed sustained release nature. The expanding composition of this invention will retain these forms in the stomach until the delay time has passed whereupon the drug will be released in a burst or pulse fashion or in a sustained fashion. Attaching, or partially embedding, several such tablets, each timed with a different delay to release, to the composition of this invention, allows versatile dosing schemes from one taken dose. For example, one could deliver three (or more) timed doses in a pulse fashion while the patient needs to take the dose only once. The three doses would mimic taking three doses of the drug at the prescribed times, with the drug being absorbed from the stomach with each dose. Such dosing allows for improved compliance to dosage schedules and in many cases will lead thereby to improved therapy. Delayed dosage forms that are not coupled to gastric retention will deliver each such dose in a different part of the GI tract with different absorption profiles for each of the doses. Such therapy would not be equivalent to taking three doses of the drug at the prescribed times, wherein the drug would have been absorbed from the stomach in each case.
In addition to the above-described dosage forms, there are many other dosage forms in which the drug delivery vehicle could be used to deliver a therapeutic bis-phosphonate over a sustained period in the stomach.
Having thus described the invention with reference to certain preferred embodiments, other embodiments will become apparent to one skilled in the art from consideration of the specification and examples. It is intended that the specification, including the examples, is considered exemplary only, with the scope and spirit of the invention being indicated by the claims which follow.