Porous drug matrices and methods of manufacture thereof

Abstract

Drugs, especially low aqueous solubility drugs, are provided in a porous matrix form, preferably microparticles, which enhances dissolution of the drug in aqueous media. The drug matrices preferably are made using a process that includes (i) dissolving a drug, preferably a drug having low aqueous solubility, in a volatile solvent to form a drug solution, (ii) combining at least one pore forming agent with the drug solution to form an emulsion, suspension, or second solution and hydrophilic or hydrophobic excipients that stabilize the drug and inhibit crystallization, and (iii) removing the volatile solvent and pore forming agent from the emulsion, suspension, or second solution to yield the porous matrix of drug. Hydrophobic or hydrophilic excipients may be selected to stabilize the drug in crystalline form by inhibiting crystal growth or to stabilize the drug in amorphous form by preventing crystallization. The pore forming agent can be either a volatile liquid that is immiscible with the drug solvent or a volatile solid compound, preferably a volatile salt. In a preferred embodiment, spray drying is used to remove the solvents and the pore forming agent. The resulting porous matrix has a faster rate of dissolution following administration to a patient, as compared to non-porous matrix forms of the drug. In a preferred embodiment, microparticles of the porous drug matrix are reconstituted with an aqueous medium and administered parenterally, or processed using standard techniques into tablets or capsules for oral administration.

Description

BACKGROUND OF THE INVENTION This invention generally relates to formulations of drugs, especially drugs having low solubility, and more particularly to methods of making formulations of such drugs to enhance their rate of dissolution, and optionally, to enhance their stability through the inclusion of hydrophobic or hydrophilic excipients that enhance dissolution rate, stabilize drug in crystalline form by inhibiting crystal growth or stabilize drug in amorphous form by preventing crystallization. The bioavailability of a drug can be limited by poor dissolution of the drug into aqueous bodily fluids following administration. This rate-limiting step may therefore be critical to rapidly attaining therapeutically effective drug levels. Traditional approaches to parenteral delivery of poorly soluble drugs include using large volumes of aqueous diluents, solubilizing agents, detergents, non-aqueous solvents, or non-physiological pH solutions. These formulations, however, can increase t...

AI Technical Summary

Benefits of technology

Drugs are provided in a porous matrix form wherein the dissolution rate of the drug is enhanced when the matrix is contacted with an aqueous medium. In a preferred embodiment, low aqueous solubility drugs are provided in a porous matrix form that forms microparticles when the matrix is contacted with an aqueous medium. Upon contact with an aqueous medium, the porous matrix containing low aqueous solubility drugs yields microparticles having a mean diameter between about 0.1 and 5 μm and a total surface area greater than about 0.9 m2 / mL. The dry porous matrix is in a dry powder form having a TAP density less than or equal to 1.0 g / mL and / or having a total surface area (sum of internal and external surface area) of greater than or equal to 0.2 m2 / g. The porous matrices that contain the drug are preferably made using a process that includes (i) dissolving a drug in a volatile solvent to form a drug solution, (ii) combining at least one pore forming agent with the drug solution to form an emulsion, suspension, or second solution, and (iii) removing the volatile solvent and pore forming agent from the emulsion, suspension, or second solution to yield the dry porous matrix of drug. The resulting porous matrix has a faster rate of dissolution following administration to a patient, as compared to non-porous matrix forms of the drug. The pore forming agent can be either a volatile liquid that is immiscible with the drug solvent or a volatile solid compound, preferably a volatile salt. If the pore forming agent is a liquid, the agent is emulsified with the drug solution. If the pore forming agent is a solid, the agent is (i) dissolved in the drug solution, (ii) dissolved in a solvent that is not miscible in the drug solvent and then emulsified with the drug solution, or (iii) suspended as solid particulates in the drug solution. Optionally, hydrophilic or hydrophobic excipients, polymers, pegylated agents, wetting agents, and / or tonicity agents may be added to the drug solvent, the pore forming agent solvent, or both. In the preferred embodiment, at least one excipient incorporated into the emulsion, suspension, or second solution, is a hydrophobic and hydrophilic excipient which enhances dissolution rate, which stabilizes drug in amorphous form by preventing crystallization, or which stabilizes drug in crystalline form by inhibiting crystal growth. In another embodiment, the matrix further includes a pegylated excipient, such as pegylated phospholipid, with the drug. The pegylated excipient shields the drug from macrophage uptake, which prolong its half-life or enhance bioavailability of the drug. The solution, emulsion, or suspension of the pore forming agent in the drug solution is then processed to remove the drug solvent and the pore forming agent, as well as any pore forming agent solvent. In a preferred embodiment, spray drying, optionally followed by lyophilization, fluid bed drying, or vacuum drying, is used to remove the solvents and the pore forming agent. Sugars, amino acids, or polymers can all stabilize the drug forming the porous drug matrix, depending on the molecule to be stabilized.

An advantage of the formulations is that they can be administered as a bolus, when the drug normally must be infused to avoid precipitation of the drug. By avoiding precipitation of drug in vivo, the formulations can also be administered parenterally. An additional advantage is the formulations can be administered in reduced volumes.

Problems solved by technology

The bioavailability of a drug can be limited by poor dissolution of the drug into aqueous bodily fluids following administration.

These formulations, however, can increase the systemic toxicity of the drug composition or damage body tissues at the site of administration.

Nanoparticles, however, can be difficult to produce and maintain in a stable form due to the tendency of the nanoparticles to flocculate or agglomerate, particularly without the presence of surface modifying agents adsorbed or coated onto the particles.

Furthermore, milling or wet grinding techniques, which are typically employed for nanonization, can be undesirable, as it can take several days to process a single batch, scaling-up of the milling or grinding process can be difficult and / or costly, the process can be difficult to conduct aseptically, and it is difficult to eliminate shedding of milling media into the product.

Such large beads, however, are unsuitable for parenteral administration, and the beads have less surface area and slower dissolution rates than smaller particles.

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