Abstract:
The invention is a controlled release composition comprising a therapeutic amount of an active ingredient in a controlled release matrix. The matrix comprises a combination of a pharmaceutically acceptable acrylic polymer and a metal hydroxide. The amount of surfactant, relative to a given amount of acrylic polymer, is selected for and corresponds to a predetermined release rate for said active ingredient. The compound is preferably used to provide controlled release dosage of oxycodone through a matrix of ammonio methacrylic polymer and sodium lauryl sulfate.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a controlled release therapeutic compound employing a controlled release matrix including acrylic polymer and a surfactant. More particularly, the invention relates to a compound wherein the rate of release of an active ingredient is determined by the ratio of surfactant to acrylic polymer in the compound. Most particularly, the invention relates to a controlled release compound incorporating a therapeutic agent into a controlled release matrix including ammonio methacrylic polymer and sodium lauryl sulfate. 
         [0003]    2. Description of the Related Art 
         [0004]    Many medical conditions are best treated by administration of a pharmaceutical in such a way as to sustain its action over an extended period of time. Many delivery systems have been developed over time for providing such treatments. These products have become known as sustained release, controlled release, time release, etc. Each of these designations is nearly synonymous with the others. The term controlled release is used herein for convenience, and is not intended to be distinguished from the other terms in the art. Regardless of the term, the concept behind each as used herein is prolonged delivery of active ingredient over time via an oral dosage form. 
         [0005]    Controlled release preparations provide a longer duration of pharmacological response after administration than is ordinarily experienced after the administration of an immediate release dosage form. Such extended periods of response provide for many inherent therapeutic benefits that are not achieved with short acting, immediate release products. This kind of pharmaceutical administration can be useful for treating chronic pain, such as that associated with rheumatic or arthritic conditions. Controlled-release dosage forms can also be used beneficially in the administration of a variety of drugs whose sustained action is important to their efficacy in treating many conditions. 
         [0006]    Many physiological factors influence both the gastrointestinal transit time and the release of a drug from a controlled release dosage form, and thus influence the uptake of the drug of the patient&#39;s system. Ideally, such controlled-release dosage forms should release the active pharmaceutical ingredient at a controlled rate such that the amount of active pharmaceutical ingredient which is available in the body to treat the condition is maintained at a relatively constant and desired level over an extended period of time. That is, it is desirable that the active pharmaceutical ingredient be released at a reproducible, predictable rate. 
         [0007]    Many controlled release formulations are known in the art. Included among these are specially coated beads or pellets, coated tablets, and ion exchange resins, wherein the slow release of the active drug is brought about through selective breakdown of, or permeation through, the coating of the preparation or through formulation with a special matrix to effect the release of the drug. 
         [0008]    Several controlled release products incorporate fast-release and slow-release components. The combination allows for quick entry of active ingredient during initial treatment periods, while permitting a sustaining effect through later release during subsequent hours. Multiple, alternative layers of coatings and medicine, as well as coated and uncoated medicaments have been used to create this effect. 
         [0009]    Some controlled release products use specially designed excipient matrices, which determine the rate of release. Special cellulose-derived matrices have been developed for this purpose. Specifically, plasticized ethylcellulose materials have been found to be effective. The specific composition and structure of these materials exhibit desired properties for the controlled release of the desired therapeutic agent. Other types of controlled release mechanisms are also known. 
         [0010]    In the case of controlled release coatings, often a polymeric material, such as acrylic polymer, is used to coat a tablet or other dosage form. The particular polymer used has a disintegration of dissolution factor associated with it, correlating to the controlled rate of release of the therapeutic agent. Another benefit of these coatings is their ability to mask undesirable medicinal tastes. In some cases, the acrylic polymer has been blended into the excipient material as filler material in addition to use as the controlled release coating. 
         [0011]    However, heretofore there has been no teaching of a controlled release formulation providing a pharmacologically active ingredient in a novel excipient matrix combining suitable proportions of an acrylic polymer and surfactant for controlling release rates of such as active ingredient. 
       SUMMARY OF THE INVENTION 
       [0012]    A controlled release composition consists of a therapeutic amount of an active ingredient in a controlled release matrix. The matrix comprises a combination of a pharmaceutically acceptable acrylic polymer and a surfactant. The amount of surfactant, relative to the amount of acrylic polymer, is selected for and corresponds to a pre-determined release rate for said active ingredient. The compound is preferably used to provide controlled release dosages of oxycodone through a matrix of ammonio methacrylic polymer and sodium lauryl sulfate. 
     
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0013]    The sole FIGURE is a graph depicting the release rate over time with various surfactant levels. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    The invention uses a controlled release matrix to control the release of a therapeutic ingredient. The compound can be formed into suitable solid oral dosage forms by any suitable method as is commonly known in the art. Tablets are the preferred dosage form. To obtain controlled release effects, the matrix comprises a combination of an acrylic polymer and surfactant. Reliance on a controlled release coating is unnecessary. 
         [0015]    Many conditions may benefit from the prolonged treatment effects of controlled release products. Accordingly, many therapeutically active ingredients may be used in a controlled release manner. Pain medications are perhaps most visibly effective when administered through controlled release methods. Thus, although oxycodone and its pharmaceutically active salts are preferred, many other active ingredients may be used. Morphine and its pharmaceutically acceptable salts, oxymorphone, hydromorphone, levorphanol, codeine, hydrocodone, oxycodone, nalorphine, naloxone, naltrexone, buprenorphine, butorphanol, nalbuphine, and other common narcotics and analgesics are non-limiting examples of such active ingredients. 
         [0016]    Unlike prior art of sustained or controlled release products, the acrylic polymer in the present invention is used as a dry excipient, and not a controlled release coating. It is to be understood that the polymer may be present as coating, but is not necessary to achieve the desired results. The acrylic polymer is combined with the surfactant into a homogeneous matrix into which the active ingredient is introduced. Surprisingly, the inventors have discovered that the rate of release of the active ingredient can be unexpectedly controlled by varying the ratio of surfactant to acrylic polymer, rather than rely solely on the rate of disintegration or dissolution of the acrylic polymer. With this discovery, the amount of active ingredient and acrylic polymer may be kept constant while achieving various release rates solely through manipulation of the amount of surfactant in the controlled release matrix. A ratio of surfactant to acrylic polymer (S/P) of approximately 0.005-0.5 by weight is contemplated by the inventors. A preferred ratio of approximately 0.02-0.2 by weight has been effective. 
         [0017]    The preferred acrylic polymer is methacrylate based. Most specifically, an ammonio methacrylate polymer readily available under the tradename Eudragit RSPO is preferred. As discussed above, Eudragit is cited in the prior art for coatings. The polymer may account for a wide range of proportions in the tablet as long as the proper S/P ratio is mentioned. 
         [0018]    Any surfactants may be used. Preferably, anionic surfactant is used. Most preferably, the surfactant is sodium lauryl sulfate. Minimal amounts of sodium lauryl sulfate, about 1-5% by total tablet weight, have been found to be effective. The amount of surfactant for a given amount of polymer is preferably selected based upon the desired release rate. The FIGURE illustrates the effects of compounds prepared with 0, 1, 3, and 5% sodium lauryl sulfate, corresponding to 0.02, 0.06, and 0.1 S/P respectively. As shown, the rate of release of the active ingredient is greatly reduced as the S/P ratio increases. Controlled dosages over 12, 18, and 24 hours or other increments are possible through manipulation of the S/P ratio. 
         [0019]    Ultimately, the compound is shaped into a solid, oral dosage form according to known techniques. Dry granulation techniques are currently preferred, although the invention is not limited to these techniques alone. Other material including, but not limited to, binders, fillers, and gelling agents may be used in the matrix to form appropriately sized and shaped dosage forms. A matrix including only the acrylic polymer and the surfactant is capable of satisfactory dosage formation without the use of these additional materials, but most applications will use at least some amount of filler material. It should be appreciated that these materials are inert and generally are present mainly to aid in solid dosage (i.e. tablet) formation or other functions. 
         [0020]    A graph plotting the percent of release versus time illustrates the effect of varying sodium lauryl sulfate concentration in the compound. All tests were performed according to USP apparatus II at a speed of 50 rpm in 900 mL dissolution medium. Four test samples were prepared at 150 mg each. Each contained approximately 10 mg oxycodone hydrochloride as the active ingredient and Eudragit RSPO as the acrylic polymer at 50% by weight of the composition. The first sample is a control without surfactant. The remaining samples had 1, 3, and 5% sodium lauryl sulfate (SLS), by weight of the composition, as the surfactant, corresponding to surfactant/polymer ratios (S/P) of 0.02, 0.06, and 0.1, respectively. The tables below show the various compositions, including various additives which are commonly added as fillers, preservatives, etc. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Oxycodone Hydrochloride Extended Release Tablets, 
               
               
                 10 mg, (control) (0 S/P) 
               
             
          
           
               
                   
                   
                 Quantity 
                 Quantity 
               
               
                   
                 Excipients 
                 mg/tablet 
                 (%) 
               
               
                   
                   
               
             
          
           
               
                   
                 Oxycodone Hydrochloride 
                 10 
                 6.7%   
               
               
                   
                 Microcrystalline Cellulose 
                 48.5 
                 32.3%   
               
               
                   
                 Ammonio Methacrylate Copolymer 
                 75 
                 50%  
               
               
                   
                 Collodial Silicon Dioxide 
                 3 
                 2% 
               
               
                   
                 Sodium Lauryl Sulfate 
                 0 
                 0% 
               
               
                   
                 Povidone 
                 7.5 
                 5% 
               
               
                   
                 Stearic Acid 
                 3 
                 2% 
               
               
                   
                 Magnesium Stearate 
                 3 
                 2% 
               
               
                   
                 Tablet Weight 
                 150 
                 100%  
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Oxycodone Hydrochloride Extended Release Tablets, 
               
               
                 10 mg, (0.02 S/P) 
               
             
          
           
               
                   
                   
                 Quantity 
                 Quantity 
               
               
                   
                 Excipients 
                 mg/tablet 
                 (%) 
               
               
                   
                   
               
             
          
           
               
                   
                 Oxycodone Hydrochloride 
                 10 
                 6.7%   
               
               
                   
                 Microcrystalline Cellulose 
                 47 
                 31.3%   
               
               
                   
                 Ammonio Methacrylate Copolymer 
                 75 
                 50%  
               
               
                   
                 Collodial Silicon Dioxide 
                 3 
                 2% 
               
               
                   
                 Sodium Lauryl Sulfate 
                 1.5 
                 1% 
               
               
                   
                 Povidone 
                 7.5 
                 5% 
               
               
                   
                 Stearic Acid 
                 3 
                 2% 
               
               
                   
                 Magnesium Stearate 
                 3 
                 2% 
               
               
                   
                 Tablet Weight 
                 150 
                 100%  
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Oxycodone Hydrochloride Extended Release Tablets, 
               
               
                 10 mg, H/P = .06 
               
             
          
           
               
                   
                   
                 Quantity 
                 Quantity 
               
               
                   
                 Excipients 
                 mg/tablet 
                 (%) 
               
               
                   
                   
               
             
          
           
               
                   
                 Oxycodone Hydrochloride 
                 10 
                 6.667%    
               
               
                   
                 Microcrystalline Cellulose 
                 44 
                 29.3%   
               
               
                   
                 Ammonio Methacrylate Copolymer 
                 75 
                 50%  
               
               
                   
                 Collodial Silicon Dioxide 
                 3 
                 2% 
               
               
                   
                 Sodium Lauryl Sulfate 
                 4.5 
                 3% 
               
               
                   
                 Povidone 
                 7.5 
                 5% 
               
               
                   
                 Stearic Acid 
                 3 
                 2% 
               
               
                   
                 Magnesium Stearate 
                 3 
                 2% 
               
               
                   
                 Tablet Weight 
                 150 
                 100%  
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Oxycodone Hydrochloride Extended Release Tablets, 
               
               
                 10 mg, (0.1 S/P) 
               
             
          
           
               
                   
                   
                 Quantity 
                 Quantity 
               
               
                   
                 Excipients 
                 mg/tablet 
                 (%) 
               
               
                   
                   
               
             
          
           
               
                   
                 Oxycodone Hydrochloride 
                 10 
                 6.7%   
               
               
                   
                 Microcrystalline Cellulose 
                 41 
                 27.3%   
               
               
                   
                 Ammonio Methacrylate Copolymer 
                 75 
                 50%  
               
               
                   
                 Collodial Silicon Dioxide 
                 3 
                 2% 
               
               
                   
                 Sodium Lauryl Sulfate 
                 7.5 
                 5% 
               
               
                   
                 Povidone 
                 7.5 
                 5% 
               
               
                   
                 Stearic Acid 
                 3 
                 2% 
               
               
                   
                 Magnesium Stearate 
                 3 
                 2% 
               
               
                   
                 Tablet Weight 
                 150 
                 100%  
               
               
                   
                   
               
             
          
         
       
     
         [0021]    From the above, it is readily apparent that during the tests only the amount of surfactant, sodium lauryl sulfate was varied, with the amount of microcrystalline cellulose adjusted accordingly; all other components were equal in each sample. The microcrystalline cellulose is a well known and widely used filler material which is not used to achieve controlled release effects. This type of filler has been shown to aid in tablet formation. Accordingly, the dramatic effect on the release rates of the various compounds can only be attributed to the variation in the amount of surfactant with respect to the acrylic polymer. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Release Profile of formulations from Tables 1–4 
               
             
          
           
               
                   
                   
                 1% SLS, 
                 3% SLS, 
                 5% SLS, 
               
               
                 Time (hr) 
                 0% SLS, H/P = 0 
                 H/P = 0.02 
                 H/P = 0.06 
                 H/P = 0.1 
               
               
                   
               
             
          
           
               
                 0.5 
                 33 
                 28 
                 24 
                 17 
               
               
                 1 
                 47 
                 40 
                 34 
                 24 
               
               
                 2 
                 66 
                 57 
                 49 
                 32 
               
               
                 3 
                 79 
                 69 
                 60 
                 38 
               
               
                 4 
                 88 
                 78 
                 68 
                 43 
               
               
                 5 
                 94 
                 83 
                 73 
                 47 
               
               
                 6 
                 98 
                 87 
                 77 
                 51 
               
               
                 8 
                 102 
                 91 
                 82 
                 57 
               
               
                 10 
                 103 
                 93 
                 86 
                 61 
               
               
                 12 
                 104 
                 95 
                 88 
                 65 
               
               
                   
               
             
          
         
       
     
         [0022]    Referring again to the FIGURE, the differences in the rate of release between the various compounds become readily apparent as early as one half hour where the control sample released approximately 33% of its active ingredient compared to approximately 28%, 24%, and 17% respectively for the 1% (0.02 S/P), 3% (0.06 S/P), and 5% (0.1 S/P) samples. After three hours, the control releases about 80% of its active ingredient. The SLS containing samples exhibit a nearly congruent path compared to the control, shifted due to increased controlled release effects. The 1% (0.02 S/P) and 3% (0.06 S/P) sample released approximately 70 and 60% of their active ingredients, respectively, after three hours. The change in the rate of release is even more dramatic in the 5% (0.1 S/P) sample, and released less than 40% of its active ingredient in the same period. It is clear that manipulation of release rates is possible through controlling the ratio of SLS to polymer in the composition.