Drug – bio-affecting and body treating compositions – Effervescent or pressurized fluid containing – Organic pressurized fluid
Reexamination Certificate
1999-04-06
2002-05-07
Bawa, Raj (Department: 1619)
Drug, bio-affecting and body treating compositions
Effervescent or pressurized fluid containing
Organic pressurized fluid
C424S401000, C424S046000, C424S451000, C424S436000, C514S944000
Reexamination Certificate
active
06383471
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to drug delivery systems, and in particular to pharmaceutical compositions for the improved delivery of ionizable hydrophobic compounds and methods therefor.
BACKGROUND
Hydrophobic therapeutic agents, i.e., therapeutic compounds having poor solubility in aqueous solution, present difficult problems in formulating such compounds for effective administration to patients. A well-designed formulation must, at a minimum, be capable of presenting a therapeutically effective amount of the hydrophobic compound to the desired absorption site, in an absorbable form. Even this minimal functionality is difficult to achieve when delivery of the hydrophobic therapeutic agent requires interaction with aqueous physiological environments, such as gastric fluids and intestinal fluids. Pharmaceutical compositions for delivery of such hydrophobic therapeutic agents must carry the hydrophobic compound through the aqueous environment, while maintaining the hydrophobic compound in an absorbable form, and avoiding the use of physiologically harmful solvents or excipients.
A number of approaches to formulating hydrophobic therapeutic agents for oral or parenteral delivery are known. Such approaches include, for example, formulations in which the hydrophobic therapeutic agent is present in an oil-in-water emulsion, a microemulsion, or a solution of micelles, liposomes, or other multi-lamellar carrier particles. While such approaches may be appropriate for some ionizable as well as non-ionizable hydrophobic therapeutic agents, they fail to take advantage of the unique acid-base chemical properties, and associated solubility properties, of ionizable compounds.
In particular, unlike non-ionizable hydrophobic therapeutic agents, ionizable hydrophobic therapeutic agents can be rendered soluble in aqueous solution if the pH of the solution is adjusted to ionize the therapeutic agent. Such an approach is well known in the art. For example, U.S. Pat. No. 5,773,029 is directed to a pharmaceutical composition of an acidic drug, wherein the solubility of the acidic drug is enhanced by simultaneous salt formation with an organic or inorganic base and complexation with a cyclodextrin. The resultant drug/cyclodextrin/base complexes reportedly are readily soluble in water in high concentrations.
U.S. Pat. No. 5,360,615 discloses a pharmaceutical carrier system for an acidic, basic or amphoteric pharmaceutical agent in which the pharmaceutical agent is partially ionized by an acid or base in a polyethylene glycol-based solvent system. The pharmaceutical agent reportedly shows enhanced solubility in the partially ionized form. The reference also discloses that addition of glycerin, propylene glycol and/or polyvinylpyrrolidone further enhances the solubility of the pharmaceutical agent in the polyethylene glycol base. However, the invention is limited to polyethylene glycol-based solvent systems and a narrow range of ionizing agent concentration, and there is no disclosure of other solvent systems. Thus, its utility is severely limited.
Similarly, U.S. Pat. No. 5,376,688 discloses a pharmaceutical solution of an acidic, basic or amphoteric pharmaceutical agent. The solution includes a pharmaceutical agent, an ionizing species, and a solvent system. The solvent system can be diethylene glycol monoethyl ether, glycerol caprylate/caprate, polyglycerol oleate, alpha-hydro-w-hydroxypoly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) block copolymers, or mixtures of those components. The solvent system can also be a mixture of polyethylene glycol and a polyoxyethylene sorbitan ester. Optional components include water, glycerin, propylene glycol, and polyvinylpyrrolidone. However, the invention is limited to these particular compounds and a narrow range of ionizing agent concentration, rendering its utility severely limited. Moreover, some of the solvent system components show poor or questionable biocompatibility, and thus would be impractical for drug delivery to a patient.
A further problem with conventional approaches to solubilizing ionizable hydrophobic therapeutic agents is the difficulty in maintaining the solubilized therapeutic agent in solubilized form. Thus, for example, while ionizing an acidic therapeutic agent with a base may increase its solubility, the therapeutic agent is prone to precipitation in the gastrointestinal tract due to the acidic pH conditions encountered upon administration to a patient, and the approximately 10 to 100-fold dilution expected in gastrointestinal or intestinal fluids. This precipitation is particularly disadvantageous, since the precipitated therapeutic agent is essentially unavailable for absorption, leading to difficulties in controlling dosages, and a need to administer large doses of the therapeutic agent to ensure that a therapeutically effective amount reaches the absorption site in a bioavailable form. Such difficulties necessarily result in increased costs, and compromised patient safety and therapeutic effectiveness.
Thus, there is a need for versatile and effective pharmaceutical compositions that overcome these deficiencies in the prior art.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide pharmaceutical compositions capable of solubilizing therapeutically effective amounts of ionizable hydrophobic therapeutic agents.
It is another object of the invention to provide pharmaceutical compositions capable of maintaining a solubilized ionizable hydrophobic therapeutic agent in solubilized form upon administration to a patient.
It is another object of the invention to provide pharmaceutical compositions of ionizable hydrophobic therapeutic agents with improved delivery of the therapeutic agent to the absorption site.
It is a further object of the invention to provide improved methods of preparing pharmaceutical compositions of ionizable hydrophobic therapeutic agents.
It is still another object of the invention to provide methods of treating an animal with pharmaceutical compositions of ionizable hydrophobic therapeutic agents.
In accordance with these and other objects and features, the present invention provides pharmaceutical compositions and methods for improved delivery of ionizable hydrophobic therapeutic agents.
In one embodiment, the invention is directed to a pharmaceutical composition including an ionizable hydrophobic therapeutic agent and a carrier. The carrier includes an ionizing agent to ionize the therapeutic agent, and a surfactant. Optionally, the carrier also includes solubilizers, triglycerides and neutralizing agents.
In another embodiment, the invention is directed to a pharmaceutical composition including a hydrophobic therapeutic agent having at least one ionizable functional group, and a carrier. The carrier includes an ionizing agent capable of ionizing the functional group, a surfactant, and a triglyceride.
In another embodiment, the invention is directed to a pharmaceutical composition including a hydrophobic therapeutic agent having at least one ionizable functional group and a carrier, wherein the carrier includes an ionizing agent capable of ionizing the ionizable functional group and present in a pre-reaction amount of greater than about 1.5 mole equivalents per mole of ionizable functional group, and a surfactant. In a further aspect of this embodiment, the composition further includes a neutralizing agent capable of neutralizing a portion of the ionizing agent.
In another embodiment, the invention is directed to a pharmaceutical composition including a hydrophobic therapeutic agent having at least one ionizable functional group, and a carrier, wherein the carrier includes an ionizing agent capable of ionizing the ionizable functional group, a surfactant, and a solubilizer present in an amount of greater than about 10% by weight, based on the total weight of the composition. In this embodiment, the surfactant includes at least one compound from the group consisting of alkylglucosides; alkylmaltosides; alkylthioglucosides; lauryl macrogolglycerides; po
Chen Feng-Jing
Patel Mahesh V.
Bawa Raj
Lipocine Inc.
Reed Dianne E.
Reed & Associates
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