Abstract:
A substantially anhydrous foamable composition capable of forming a substantially stable foam on contact with water is formed from a mixture of water soluble polysaccharide gum, an effervescent base and a biocompatible gelling salt. These compositions upon contact with water form extremely stable foams which are capable of acting as carriers for pharmaceutically active compositions.

Description:
BACKGROUND OF THE INVENTION 
     The use of foams for pharmaceutical purposes is well known particularly in the field of contraception as vaginal foams and in the treatment of hyperacidity as antiacid foams. The effectiveness of both types of foams has been hindered by the short life such foams in the aqueous environment in which both find themselves. While foaming action is quite simple to initiate, the very presence of the environmental aqueous fluids which initiate the foaming serve to rapidly dilute the foam to a point where it no longer exists in this form. A composition capable of foaming rapidly on the one hand but producing a foam with a substantial foam life is a long felt need. Such foaming compositions, provided that they are made of biochemically compatible materials, can be utilized as carriers or sustained release devices for numerous pharmaceutically active compositions. 
     SUMMARY OF THE INVENTION 
     It has been found that substantially anhydrous compositions capable of forming a substantially stable foam on contact with water may be formulated from mixtures comprising a water soluble polysaccharide gum, a water soluble biocompatible calcium or potassium gelling salt and an effervescent base comprising an alkali metal carbonate or bicarbonate and a water soluble biocompatible acid or acid salt. Such compositions may be compounded with a predetermined pharmaceutically active material and provided in any of the usual dosage forms such as tablets, capsules, powders, granules, or suppositories. The compositions may then be administered in a conventional manner suitable for their intended purpose. Suitable loci for administration are per os for gastrically active compositions and intravaginally for vaginal contraceptives, buffers and the like. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The substantially anhydrous foamable compositions of the present invention comprise 20 to 75 parts by weight, suitably about 30 to 50 parts by weight of a water soluble polysaccharide gum. Among the suitable gums may be mentioned the water soluble alginate salts such as sodium or potassium alginate and kappa carrageenan as well as iota carrageenan. There is also provided a gelling agent to provide a rubbery polymer salt, said salt comprising between about 10 to about 50, suitably between about 20 to about 30 parts by weight of the total composition. The gelling salt can be any water soluble biocompatible calcium salt such as the gluconate, lactate, chloride, or less soluble salts if required for slower gelling such as carbonate or phosphate. Where kappa carrageenan is utilized as the polysaccharide gum, the corresponding potassium salts may be employed. It is preferred to utilize an amount of water soluble salt corresponding to between 10 and 100% by weight of the gum in the composition. 
     The foaming effect is achieved by the presence of an effervescent base (the term base here not being utilized in its meaning sense as opposite or complementary to acid). The base comprises a gas generating component most suitably a carbonate or bicarbonate, preferably sodium or potassium bicarbonate and an acid component selected from any solid water soluble biocompatible acid such as the fruit acids suitably tartaric, malic, fumaric, adipic or citric acids, or acid salts such as sodium biphosphate. In the preferred embodiment of the invention, substantially equal parts by weight of the gas generating component and the acid are utilized. 
     A large variety of pharmaceutically active compositions can be incorporated into the compositions and the compositions formulated into conventional modes of administration. 
     For purposes of the following discussion, the standard dosage unit will be considered as comprising one gram of gum, 0.5 grams of alkali metal bicarbonate, 0.5 grams of biocompatible acid, and 0.5 grams of gelling salt. Such a dosage unit is merely considered to be illustrative and no way to be considered as limiting the scope of the present invention. 
     A vaginal contraceptive composition may be prepared comprising the basic foamable composition and a spermicide. Any known vaginally active spermicide may be employed in particular, there may be mentioned nonoxynol-9, octoxonol or mefengol. These are compounded in dosages of between 50 to 200, suitably between 75 and 100 mg. per dosage unit. 
     A vaginal buffering agent may be provided by increasing the amount of the biocompatible acid by between 250 and 1,000, most suitably between 300 and 500 mg./dosage unit of acid. 
     Another use for the compositions may be found as gastric antiacid agents. In this composition, there are additionally utilized carbonates such as calcium or magnesium carbonate or the hydroxides of aluminum, magnesium, or bismuth. These are merely considered to be the common and exemplary materials but other biocompatible bases could also be employed. 
     The stable nature of the foam produced by the foaming compositions of the present invention makes the foams particularly suitable as gastrio-intestinal depots operating as sustained release agents for a variety of pharmacologically active agents which are traditionally administrable by a gastric route. As exemplifying but not limiting this aspect of the invention may be mentioned sympathomimetic amines such as phenylpropanolamine and salts, ephedrine and salts, isoproterenol and salts, phenylephrine and salts or pseudoephedrine and salts, antihistimes such as chlorpheniramine, diphenhydramine, docylamine, phenyltoloxamine, pyrilamine, tripelenamine, pheniramine, brompheniramine, dexbrompheniramine, dexchlorpheniramine, promethazine, meclizine or cyclizine, antitussives such as dextromethorphan, benzonatate, noscapine, carbetapentane citrate, caramiphen ethane disulfonate, or chlorphedianol, analgesics such as aspirin, acetaminophen, salicylamide, sodium silicylate, indomethacin, ibuprofen or phenylbutazone, and muscle relaxants such as carisoprodol, methocarbamol or meprobamate. 
     It will be understood by those skilled in the art that pharmaceutically inert excipients, diluents and the like can be included in the compositions as desired. 
     The special advantage of the compositions of the present invention lies in the desirable combination of immediate action and long life compared to conventional foams. For example, currently available vaginal contraceptives tablets and suppositories require a 10 to 15 minute waiting period for the foam to develop as opposed to the 2 to 5 minute time required by the present compositions, and the present compositions maintain their structure for up to 6 hours as opposed to one hour for conventional products. These two properties are extremely important in considering the esthetics of use as vaginal contraceptives permitting on the one hand substantially instantaneous intercourse where this is desired and on the other hand, an unobvious &#34;preplanning&#34; if that approach is desired. 
    
    
     SPECIFIC FORMULATIONS 
     
         ______________________________________Material             Mg/dosage Unit______________________________________EXAMPLE IVaginal Contraceptive CompositionSodium Alginate      500Sodium Bicarbonate   500Citric Acid          500Calcium Gluconate    200Nonoxynol 9          100Lactose              500TOTAL                2,300EXAMPLE IIVaginal Buffering Agent (pH 4-5) Molded SuppositorySodium Alginate      850Sodium Bicarbonate   500Citric Acid          1,000Calcium Gluconate    200Polyethylene Glycol 1540                1,000Polyethylene Glycol 4000                250TOTAL                3,300______________________________________ 
    
     The mixtures of Examples I and II can be granulated to be compressed in a conventional tableting machine. 
     
         ______________________________________EXAMPLE IIIGastric Antiacid MaterialMaterial         Mg/dosage Unit______________________________________Iota carrageenan 200Sodium Bicarbonate            150Tartaric Acid    150Calcium Carbonate            100Aluminum hydroxide            200Magnesium hydroxide            200TOTAL            1,000______________________________________ 
    
     This mixture can be granulated to be compressed in a conventional tableting machine or filled into a powder dispenser. 
     
         ______________________________________EXAMPLE IVAntihistamine CompositionFormula             Per Dose (2 tablets)______________________________________Pseudoephedrine     120 mg.  (a 12 hourHydrochloride                dose)Kappa carrageenan   250 mg.Sodium Bicarbonate  125 mg.Citric Acid         125 mg.Potassium Gluconate 250 mg.TOTAL               870 mg.  or 435 mg.                        per tablet______________________________________ 
    
     Process 
     Mix all ingredients, granulate with 75% isopropanol. Dry, lubricate with 1% calcium stearate and compress into tablets. 
     In accordance with the above procedure but in place of pseudoephedrine hydrochloride, there is utilized chlorpheniramine maleate 12 mg. or dextromethorphan hydrobromide 120 mg., a similar product (2 tablets, 12 hr. dose) is obtained. 
     
         ______________________________________EXAMPLE VGastric Antiacid Tablet              Per DoseFormula            (Film Coated Tablet)______________________________________Potassium Bicarbonate              500 mg.  (5 meq. K)Citric Acid        150 mg.Sodium Alginate    250 mg.Dicalcium Phosphate              100 mg.dihydrate______________________________________ 
    
     Process 
     Granulate and compress as in Example I. Film coat tablets for easy swallowing. 
     
         ______________________________________EXAMPLE VIAnalgesic CompositionFormula            Per Dose (2 tablets)______________________________________Acetaminophen,     1,300 mg.                       (an 8 hr.powder                      dose)______________________________________ 
    
     A composition is prepared in accordance with Example IV but substituting acetaminophen for pseudoephidrine. 
     Two tablets provide sustained blood levels of acetaminophen over an eight hour period equal to two divided doses of 650 mg. each at four hour intervals. 
     
         ______________________________________EXAMPLE VIIMuscle Relaxant CompositionFormula           Per Dose (2 tablets)______________________________________Carisoprodol, powder             700 mg.   (a 12 hr. dose)______________________________________ 
    
     A composition is prepared in accordance with Example IV but substituting acetaminophen for pseudoephidrine. 
     Two tablets provide sustained blood levels of carisoprodol over an eight hour period equal to two divided doses of 350 mg. each at four hour intervals. 
     
         ______________________________________EXAMPLE VIIIContraceptive Gel for delivery by means ofVaginal ApplicatorMaterial            Mg. Per Dosage Unit______________________________________Nonoxynol-9         100.0Sodium Alginate     800.0Sodium Bicarbonate  500.0Citric Acid         500.0Polyethylene Glycol 1500               1000.0Calcium Gluconate   200.0TOTAL               3100.0   mg.______________________________________