The present invention provides a gastric retention controlled drug delivery system comprising: (a) a controlled release core comprising a drug, a highly swellable polymer and a gas generating agent, said core being capable of swelling and achieving floatation rapidly while maintaining its physical integrity in gastrointestinal fluids for prolonged periods, and (b) a rapidly releasing coat composition comprising the same drug as in the core and pharmaceutically acceptable excipients, wherein the coating composition surrounds the core such that the system provides a biphasic release of the drug in gastrointestinal fluids.

Description of the Invention

OBJECT OF THE INVENTION

It is an object of the present invention to provide a gastric retention controlled drug delivery system comprising: a. a controlled release core comprising a drug, a highly swellable polymer and a gas generating agent, said core being capable of swelling and achieving flotation rapidly while maintaining its physical integrity in gastrointestinal fluids for prolonged periods, and b. a rapidly releasing coat composition comprising the same drug as in the core and pharmaceutically acceptable excipients, wherein the coating composition surrounds the core such that the system provides a biphasic release of the drug in gastrointestinal fluids.

Yet another specific object of the present invention is to provide a gastric retention controlled drug delivery system for baclofen.

SUMMARY OF THE INVENTION

The present invention provides a gastric retention controlled drug delivery system comprising: (a) a controlled release core comprising a drug, a highly swellable polymer and a gas generating compound, said core being capable of swelling and achieving floatation rapidly while maintaining its physical integrity in gastrointestinal fluids for prolonged periods, and (b) a rapidly releasing coat composition comprising the same drug as in the core and pharmaceutically acceptable excipients, wherein the coating composition surrounds the core such that the system provides a biphasic release of the drug in gastrointestinal fluids.

The present invention further provides a gastric retention controlled drug delivery system wherein the controlled release core is capable of swelling rapidly to at least about two times its original volume, and maintaining its physical integrity in gastrointestinal fluids for prolonged periods.

The present invention also provides a gastric retention controlled drug delivery system comprising baclofen or its pharmaceutically acceptable salt.

DESCRIPTION OF THE INVENTION

The present invention provides a gastric retention controlled drug delivery system comprising: (a) a controlled release core comprising a drug, a highly swellable polymer and a gas generating compound, said core being capable of swelling and achieving floatation rapidly while maintaining its physical integrity in gastrointestinal fluids for prolonged periods, and (b) a rapidly releasing coat composition comprising the same drug as in the core and pharmaceutically acceptable excipients, wherein the coating composition surrounds the core such that the system provides a biphasic release of the drug in gastrointestinal fluids.

The gastric retention controlled drug delivery system of the present invention is useful in providing improved drug delivery. Drugs that may be used in the gastric retention controlled drug delivery system of the present invention may be selected from the following, viz. alcohol abuse preparations, drugs used for alzheimer's disease, anaesthetics, acromegaly agents, analgesics, antiasthmatics, anticancer agents, anticoagulants and antithrombotic agents, anticonvulsants, antidiabetics antiemetics, antiglaucoma, antihistamines, anti-infective agents, antiparkinsons, antiplatelet agents, antirheumatic agents, antispasmodics and anticholinergic agents, antitussives, carbonic anhydrase inhibitors, cardiovascular agents, cholinesterase inhibitors, treatment of CNS disorders, CNS stimulants, contraceptives, cystic fibrosis management, dopamine receptor agonists, endometriosis management, erectile dysfunction therapy, fertility agents, gastrointestinal agents, immunomodulators and immunosuppressives, memory enhancers, migraine preparations, muscle relaxants, nucleoside analogues, osteoporosis management, parasympathomimetics, prostaglandins, psychotherapeutic agents, sedatives, hypnotics and tranquilizers, drugs used for skin ailments, steroids and hormones.

Examples of acromegaly agents are octreotide, laureotide and pegvisomant.

Examples of alcohol abuse preparations are chlorazepate, chlordiazepoxide, diazepam, disulfuram, hydroxyzine, naltrexone and their salts.

Examples of anaesthetics are adrenaline, bupivacaine, chloroprocaine, desflurane, etidocaine, levobupivacaine, lidocaine, midazolam, propofol, ropivacaine and their salts.

Examples of analgesics are acetaminophen, aspirin, bupivacain, buprenorphine, butorphanol, celecoxib, clofenadol, choline, clonidine, codeine, diflunisal, dihydrocodeine, dihydroergotamine, dihydromorphine, ethylmorphine, etodolac, eletriptan, eptazocine, ergotamine, fentanyl, fentoprofen, hyaluronic acid, hydrocodon, hydromorphon, hylan, ibuprofen, lindomethacin, ketorolac, ketotifen, levomethadon, levallorphan, levorphanol, lidocaine, mefenamic acid, meloxicam, meperidine, methadone, morphine, nabumetone, nalbuphin, nefopam, nalorphine, naloxone, naltrexone, naproxen, naratriptan, nefazodone, mormethadon, oxapozin, oxycodone, oxymorphon, pentazocin, pethidine, pehnpyramid, piritramid, piroxicam, propoxyphene, refecoxib, rizatriptan, salsalaketoprofen, sulindac, sumatriptan, tebacon, tilidin, tolmetin, tramadol, zolmitriptan and their salts.

Examples of antiasthmatics are ablukast, azelastine, bunaprolast, cinalukast, cromitrile, cromolyn, enofelast, isamoxole, ketotifen, levcromekalin, lodoxamide, montelukast, ontazolast, oxarbazole, oxatomide, piriprost potassium, pirolate, pobilukast edamine, quazolast, repirinast, ritolukast, sulukast, tetrazolastmeglumine, tiaramide, tibenelast, tomelukast, tranilast, verlukast, verofylline, zarirlukast.

Examples of anticancer agents are adriamycin, aldesleukin, allopurinol, altretamine, amifostine, anastrozole, asparaginase, betamethasone, bexarotene, bicalutamide, bleomycin, busulfan, capecitabine, carboplatin, carmustine, chlorambucil, cisplatin, cladribine, conjugated estrogen, cortisone, cyclophosphamide, cytarabine, dacarbazine, daunorubicin, dactinomycin, denileukin, dexamethasone, discodermolide, docetaxel, doxorubicin, eloposidem, epirubicin, epoetin, epothilones, estramustine, esterified estrogen, ethinyl estradiol, etoposide, exemestane, flavopirdol, fluconazole, fludarabine, fluorouracil, flutamide, floxuridine, gemcitabine, gemtuzumab, goserelin, hexamethylmelamine, hydrocortisone, hydroxyurea, idarubicin, ifosfamide, interferon, irinotecan, lemiposide, letrozole, leuprolide, levamisole, levothyroxine, lomustine, mechlorethamine, melphalan, mercaptopurine mechlorethamine, megesterol, methotrexate, methylprednisolone, methyltestosterone, mithramycin, mitomycin, mitotane, mitoxantrone, mitozolomide, mutamycin, nilutamide, paclitaxel, pamidronate, pegaspargase, pentostatin, plicamycin, porfimer, prednisolone, procarbazine, rituximab, sargramostim, semustine, streptozocin, tamoxifien, temozolamide, teniposide, testolactone, thioguanine, thiotepa, tomudex, topotecan, toremifene, trastumuzab, tretinoin, semustine, streptozolocin, valrubicin, verteprofin, vinblastine, vincristine, vindesine, vinorelbine and their salts.

Examples of anticoagulants and antithrombic agents are warfarin, dalteparin, heparin, tinzaparin, enoxaparin, danaparoid, abciximab, alprostadil, altiplase, anagralide, anistreplase, argatroban, ataprost, beraprost, camonagreel, cilostazol, clinprost, clopidogrel, cloricromen, dermatan, desirudin, domitroban, drotaverine, epoprostenol, eptifibatide, fradafiban, gabexate, iloprost, isbogrel, lamifiban, lamoteplase, lefradafiban, lepirudin, levosimendan, lexipafant, melagatran, nafagrel, nafamostsat, nizofenone, orbifiban, ozagrel, pamicogrel, parnaparin, quinobendan, reteplase, sarpogralate, satigrel, silteplase, simendan, ticlopidine, vapiprost, tirofiban, xemilofiban, Y20811 and their salts.

Examples of anticonvulsants are carbamazepine, clonazepam, clorazepine, diazepam, divalproex, ethosuximide, ethotion, felbamate, fosphenyloin, gabapentin, lamotrigine, levetiracetam, lorazepam, mephenyloin, mephobarbital, metharbital, methsuximide, oxcarbazepine, phenobarbital, phenyloin, primidone, tiagabine, topiramate, valproic acid, vigabatrin, zonisamide, and their salts.

Examples of antidiabetic agents are acarbose, acetohexamide, carbutamide, chlorpropamide, epalrestat, glibornuride, gliclazide, glimepiride, glipizide, gliquidone, glisoxepid, glyburide, glyhexamide, metformin, miglitol, nateglinide, orlistat, phenbutamide, pioglitazone, repaglinide, rosiglitazone, tolazamide, tolbutamide, tolcyclamide, tolrestat, troglitazone, voglibose and their salts.

Examples of antiemetics are alprazolam benzquinamide, benztropine, betahistine, chlorpromazine, dexamethasone, difenidol, dimenhydrinate, diphenhydramine, dolasetron, domperidone, dronabinol, droperidol, granisetron, haloperidol, lorazepam, meclizine, methylprednisolone, metoclopramide, ondansetron, perphenazine, prochlorperazine, promethazine, scopolamine, tributine, triethylperazine, triflupromazine, trimethobenzamide, tropisetron and their salts.

Examples of antiglaucoma agents are alprenoxime, dapiprazole, dipivefrin, latanoprost, naboctate, pirnabine and their salts.

Examples of antihistamines are acrivastine, activastine, albuterol, azelastine, bitolterol, alimemazine, amlexanox, azelastine, benzydamine, brompheniramine, cetirizine, chlorpheniramine, cimetidine, clemastine, cycloheptazine, cyproheptadine, diclofenac, diphenhydramine, dotarizine, ephedrine, epinastine, epinephrine, ethylnorepinephrine, fenpoterol, fexofenadine, flurbiprofen, hydroxyzine, ibuprofen, isoetharine, isoproterenol, ipratropium bromide, ketorolac, levocetirizine, loratidine, mequitazine, metaproterenol, phenylephrine, phenylpropanolamine, pirbuterol, promethazine, pseudoepedrine, pyrilamine, salmeterol, terbutaline, tranilast, xanthine derivatives, xylometazoline and their salts.

Examples of anti-infective agents are abacavir, albendazole, amantadine, amphotericin, amikacin, aminosalicylic acid, amoxycillin, ampicillin, amprenavir, atovaquin, azithromycin, aztreonam, carbenicillin, cefaclor, cefadroxil, cefamandole, cefazolin, cefdinir, cefepime, cefexime, cefoperazone, cefotaxime, cefotitam, cefoperazone, cefoxitin, cefpodoxine, cefprozil, ceftazidime, ceftibuten, ceftizoxime, ceftriaxone, cefuroxime, cephalexin, chloroquine, cidofovir, cilastatin, ciprofloxacin, clarithromycin, clavulinic acid, clindamycin, colistimethate, dalfopristine, dapsone, daunorubicin, delavirdin, demeclocycline, didanosine, doxycycline, doxorubicin, efavirenz, enoxacin, erythromycin, ethambutol, ethionamide, famsiflovir, fluconazole, flucytocin, foscarnet, fosfomycin, ganciclavir, gatifloxacin, griseofulvin, hydroxychloroquine, imipenem, indinavir, interferon, isoniazide, itraconazole, ivermectil, ketoconazole, lamivudine, levofloxacin, linizolid, lomefloxacin, lovacarbef, mebendazole, mefloquine, meropenem, methanamine, metronidazole, minocycline, moxefloxacin, naldixic acid, nelfinavir, neomycin, nevirapine, nitorfurantoin, norfloxacin, ofloxacin, oseltamivir, oxytetracycline, palivizumab, penicillins, perfloxacin, piperacillin, praziquantel, pyrazinamide, pyrimethamine, quinidine, quinupristine, retonavir, ribavirin, rifabutine, rifampicin, rimantadine, saquinavir, sparfloxacin, stavudine, streptomycin, sulfamethoxazole, teramycin, terbinafine, tetracycline, ticarcillin, thiabendazole, tobramycin, trimethoprim, trimetraxate, troleandomycin, trovafloxacin, valacyclovir, vancomycin, zalcitabine, zanamivir, zidovudine and their salts.

Examples of antiparkinsons are amantadine, adrogolide, altinicline, benztropine, biperiden, brasofensine, bromocriptine, budipine, cabergoline, CHF-1301, dihydrexidine, entacapone, etilevodopa, idazoxan, iometopane, lazabemide, melevodopa, carbidopa/levodopa, mofegiline, moxiraprine, pergolide, pramipexole, quinelorane, rasagiline, ropinirole, seligiline, talipexole, tolcapone, trihexyphenidyl and their salts.

Examples of antirheumatic agents are azathiprine, betamethasone, celecoxib, cyclosporin, diclofenac, hydroxychloroquine, indomethacin, infliximab, mercaptobutanedioic acid, methylprednisolone, naproxen, penicillamine, piroxicam, prednisolone, sulfasalazine and their salts.

Examples of platelet agents are abciximab, anagrelide, aspirin, cilostazol, clopidogrel, dipyridamole, epoprostenol, eptifibatide, ticlopidine, tinofiban and their salts.

Examples of antispasmodics and anticholinergic agents are aspirin, atropine, diclofenac, hyoscyamine, mesoprostol, methocarbamol, phenobarbital, scopolamine and their salts.

Examples of antitussives are acetaminophen, acrivastin, albuterol, benzonatate, beractant, brompheniramine, caffeine, calfactant, carbetapentane, chlorpheniramine, codeine, colfuscerin, dextromethorpham, dornase alpha, doxylamine, epinephrine, fexofenadine, guaphenesin, ipratropium, levalbuterol, metaproterenol, montelukast, pentoxyphyline, phenylephrine, phenylpropanolamine, pirbuterol, poractant alpha, pseudoephedrine, pyrilamine, salbuterol, salmeterol, terbutaline, theophylline, zafirlukast, zileuton and their salts.

Examples of carbonic anhydrase inhibitors are acetazolamide, dichlorphenamide, dorzolamide, methazolamide, sezolamide and their salts.

Examples of cardiovascular agents are abciximab, acebutolol, activase, adenosine, adrenaline, amidarone, amiloride, amlodipine, amyl nitrate, atenolol, atorvastatin, benzepril, bepiridil, betaxalol, bisoprolol, candesartan, captopril, cartenolol, carvedilol, cerivastatin, chlorthalidone, chlorthiazole, clofibrate, clonidine, colestipol, colosevelam, digoxinm, diltiazem, disopyramide, dobutamine, dofetilide, doxazosin, enalapril, epoprostenol, eprosartan, esmolol, ethacrynate, erythrityl, felodipine, fenoidapam, fosinopril, flecamide, fluorosemide, fluvastatin, gemfibrozil, hydrochlorthiazide, hydroflumethazine, ibutilide, indapamide, isosorbide, irbesartan, labetolol, lacidipine, lisinopril, losartan, lovastatin, mecamylamine, metaprolol, metaminol, metazolone, methylchlothaizide, methyldopa, metyrosine, mexiletine, midrodine, milrinonr, moexipril, nadolol, niacin, nicardipine, nicorandil, nifidepine, nimodipine, nisoldipine, nitroglycerin, phenoxybenzamine, perindopril, polythiazide, pravastatin, prazosin, procainamide, propafenone, propranolol, quanfacine, quinapril, quinidine, ranipril, reteplase, simvastatin, sotalol, spironolactone, streptokinase, telmisartan, terazosin, timolol, tocainamide, torsemide, trandolapril, triamterene, trapidil, valsartan and their salts.

Examples of cholinesterase inhibitors are donepezil, edrophonium, neostigmine, pyridostigmine, rivastigmine, tacrine and their salts.

Examples of CNS stimulants are caffeine, doxapram, dexoamphetamine, donepezil, edorphonium, methamphetamine, methylphenidate, modafinil, neostigmine, pemoline, phentermine, pyriodstigmine, rivastigmine, tacrin and their salts.

Examples of contraceptives are desogestral, ethinyl estradiol, ethynodiol, levonorgestrel, medroxyprogesterone, mestranol, norgestimate, norethindrone, norgestrel and their salts.

Examples of cystic fibrosis management are dornase alpha, pancrelipase, tobramycin and their salts.

Examples of dopamine receptor agonists are amantadine, cabergoline, fenoldopam, pergolide, pramipezal, ropinirole and their salts.

Examples of drugs used for endometriosis management are danazol, goserelin, leuprolide, nafarelin, norethindrone and their salts.

Examples of drugs used for erectile dysfunction therapy are alprostadil, sildenafil, yohimbine and their salts.

Examples of fertility agents are citrorelix, clomiphen, follitropin, ganirelix, gonadotropin, menotropin, progesterone, urofollitropin and their salts.

Examples of gastrointestinal agents are alosetron, bisacodyl, bismuth subsalicylate, celecoxib, difoxin, dipheoxylate, docusate, famotidine, glycopyrrolate, infliximab, lansoprazole, loperamide, metaclopramide, nizatidine, omeprazole, pantoprazole, rabeprazole, ranitidine, simethicone, sucralfate, and their salts.

Examples of immunomodulators and immunosupressives are azathioprin, ceftizoxine, cyclosporin, daclizumab, glatiramer, immunoglobulin, interferon, leflunomide, levamisol, mycophenolate, mausomanab, phthalidomide, ribavirine, sirolimus and their salts.

Examples of drugs used in alzheimer's disease are CP 118954, donepezil, galanthamine, metrifonate, revastigmine, tacrine, TAK-147 and their salts.

Examples of drugs used for migraine preparations are acetaminophen, dihyroergotamine, divalproex, ergotamine, propranolol, risatriptan, sumitriptan, trimetrexate and their salts. Examples of muscle relaxants are alcuronium-chloride, azapropazon, atracurium, baclofen, carisoprodol, quinine derivatives, chloromezanon, chlorophenesincarbamate, chlorozoxazon, cyclobenzaprine, dantrolen, decamethoniumbromide, dimethyltubocurariniumchloride, doxacurium, fenyramidol, gallamintriethiodide, guaiphensine, hexafluoreniumbromide, hexacarbacholinbromide, memantin, mephenesin, meprobamate, metamisol, metaxalon, methocarbamol, mivacurium, orphenadrin, pancuronium, phenazon, phenprobamate, pipecuronium, rapacuronium, rocuronium, succinylcholine, suxamethoniumchloride, tetrazepam, tizanidine, tubocurarine chloride, tybamate, vecuronium and their salts.

In preferred embodiments of the gastric retention controlled drug delivery system the muscle relaxant used is baclofen or its pharmaceutically acceptable salt. A baclofen gastric retention controlled drug delivery system is not known or disclosed or suggested prior to the present invention.

Baclofen may be used in the system in an amount ranging from about 15 mg to about 80 mg. In the gastric retention controlled drug delivery system of the present invention, baclofen is used in an amount of 30 mg. The system is designed such that a large part of the 30 mg dose of baclofen is present in the core, and is available as controlled release, while a small part of the drug is present in the coat, and is available as immediate release. Thus, a biphasic release of baclofen is provided by the delivery system of the present invention.

Examples of nucleoside analogues are abacavir, acyclovir, didanosine, gamciclovir, gemcitabine, lamivudine, ribavirin, stavudine, zalcitabine and their salts.

Examples of drugs used for osteoporosis management are alendronate, calcitonin, estradiol, estropipate, medroxyprogesterone, norethindrone, norgestimate, pamidronate, raloxifen, risdronate, zoledronate and their salts.

Examples of parasympathomimetics are bethanechol, piperidine, edrophonium, glycopyrolate, hyoscyamine, pilocarpine, tacrine, yohimbine and their salts.

Examples of prostaglandins are alprostadil, epoprostenol, misoprostol and their salts.

Examples of psychotherapeutic agents are acetophenazine, alentemol, alpertine, alprazolam, amitriptyline, apriprazole, azaperone, batelapine, befipiride, benperidol, benzindopyrine, bimithil, biriperone, brofoxine; bromperidol; bromperidol, bupropion, buspirone, butaclamol, butaperazine; butaperazin, carphenazine, carvotroline, cericlamine, chlorazepine, chlordiazepoxide, chlorpromazine; chlorprothixene, cinperene, cintriamide, citalopram, clomacran, clonazepam, clopenthixol, clopimozide, clopipazan, cloroperone, clothiapine, clothixamide, clozapine; cyclophenazine, dapiprazole, dapoxetine, desipramine, divalproex, dipyridamole, doxepin, droperidol, duloxetine, eltoprazine, eptipirone, etazolate, fenimide, flibanserin, flucindole, flumezapine, fluoxetine, fluphenazine, fluspiperone, fluspirilene, flutroline, fluvoxamine, gepirone, gevotroline, halopemide, haloperidol, hydroxyzine, hydroxynortriptyline, iloperidone, imidoline, lamotrigine, loxapine, enperone, mazapertine, mephobarbital, meprobamate, mesoridazine, mesoridazine, milnacipran, mirtazepine, metiapine, milenperone, milipertine, molindone, nafadotride, naranol, nefazodone, neflumozide, ocaperidone, odapipam, olanzapine, oxethiazine, oxiperomide, pagoclone, paliperidone, paroxitene, penfluridol, pentiapine perphenazine, phenelzine, pimozide, pinoxepin, pipamperone, piperacetazine, pipotiazine, piquindone, pirlindole, pivagabine, pramipexole, prochlorperazine, prochlorperazine, promazine, quetiapine, reboxetine, remoxipride, remoxipride, risperidone, rimcazole, robolzotan, selegiline, seperidol, sertraline, sertindole; seteptiline, setoperone, spiperone, sunipitron, tepirindole, thioridazine, thiothixene, tiapride, tioperidone, tiospirone, topiramate, tranylcypromine, trifluoperazine, trifluperidol, triflupromazine, triflupromazine, trimipramine, venlafaxine, ziprasidone and their salts.

Examples of sedatives, hypnotics and tranquilisers are bromazepam, buspirone, clazolam, clobazam, chlorazepate, diazepam, demoxepam, dexmedetomitine, diphenyhydramine, doxylamine, enciprazine, estrazolam, hydroxyzine, ketazolam, lorazatone, lorazepam, loxapine, medazepam, meperidine, methobarbital, midazolam, nabilone, nisobamate, oxazepam, pentobarbital, promethazine, propofol, triazolam, zaleplon, zolpidem and their salts.

Examples of drugs used for treatment of skin ailments are acitretin, alclometasone, allitretinoin, betamethasone, calciprotrine, chlorhexidine, clobetasol, clocortolone, clotriamozole, collagenase, cyclosporin, desonide, difluorosone, doxepine, eflornithine, finasteride, fluocinolone, flurandrenolide, fluticasone, halobetasol, hydrochloroquine, hydroquinone, hydroxyzine, ketoconazole, mafenide, malathion, menobenzone, neostigmine, nystatin, podofilox, povidone, tazorotene, tretinoin and their salts.

Examples of steroids and hormones are alclometasone, betamethasone, calcitonin, citrorelix, clobetasol, clocortolone, cortisones, danazol, desmopressin, desonide, desogestrel, desoximetasone, dexamethasone, diflorasone, estradiol, estrogens, estropipate, ethynlestradiol, fluocinolone, flurandrenolide, fluticasone, glucagon, gonadotropin, goserelin, halobetasol, hydrocortisone, leuprolide, levonorgestrel, levothyroxine, medroxyprogesterone, menotropins, methylprednisolone, methyltestosterone, mometasone, naferelin, norditropin, norethindrone, norgestrel, octreolide, oxandrolone, oxymetholone, polytropin, prednicarbate, prednisolone, progesterone, sermorelin, somatropin, stanozolol, testosterone, urofollitropin and their salts.

In accordance with this invention the core achieves a high degree of swelling in a short time. This high degree of swelling may be achieved by using highly and rapidly swellable polymers, or by avoiding a high pressure of compaction of the swellable polymers, or by use of highly swellable polymers that inherently compress to a low density. When the core that is compressed has a low density, the core has sufficient strength such that if it has to be further coated by compression then it can be transferred mechanically from the first compression station, where it is compressed, to the second compression station, where the compression coat is formed; or if it is to be further coated by spraying, then it can withstand the rigors of agitation in the coating equipment.

Examples of the highly swellable polymers that may be used in the present invention include: highly swellable grades of cellulose ethers such as hydroxy C.sub.1-4 alkyl C.sub.1-4 alkyl celluloses, carboxyalkyl celluloses, hydroxy C.sub.1-4 alkyl celluloses preferably hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropyl methylcellulose, more preferably a high viscosity grade of hydroxyethylcellulose; gums of plant, animal, mineral or synthetic origin such as (i) agar, alginates, carrageenan, furcellaran derived from marine plants, (ii) guar gum, gum arabic, gum tragacanth, karaya gum, locust bean gum, pectin derived from terrestrial plants, (iii) microbial polysaccharides such as dextran, gellan gum, rhamsan gum, welan gum, xanthan gum, and (iv) synthetic or semi-synthetic gums such as propylene glycol alginate, hydroxypropyl guar and modified starches like sodium starch glycolate; a superdisintegrant polymer such as cross-linked polyvinylpyrrolidone, cross-linked sodium carboxymethylcellulose, carboxymethyl starch, sodium carboxymethyl starch, potassium methacrylate-divinylbenzene copolymer, polyvinyl alcohols, amylose, cross-linked amylose, starch derivatives, microcrystalline cellulose and cellulose derivatives, alpha-, beta- and gamma-cyclodextrin and dextrin derivatives; an acrylic acid polymer such as cross-linked polymer available under the tradename Carbopol.RTM.; a vinyl pyrrolidone polymer such as crosslinked polyvinylpyrrolidone or crospovidone; copolymers of vinyl pyrrolidone and vinyl acetate; or mixtures thereof.

In preferred embodiments the highly swellable polymer is a mixture of a superdisintegrant and one or more binding agents, the binding agent being selected from hydrophilic polymers, preferably highly swellable polymers. In preferred embodiments, the hydrophilic polymer used is a high viscosity cellulose derivative having aqueous solution viscosity ranging from about 500 mPas to about 1,20,000 mPas. A mixture of sodium starch glycolate and high viscosity grade hydroxyethyl cellulose is used as the preferred swellable polymer in one embodiment of the present invention. In yet another embodiment, the highly swellable polymer used is a mixture of sodium starch glycolate, high viscosity grade hydroxyethyl cellulose and hydroxypropyl methylcellulose.

Sodium starch glycolate is a sodium salt of carboxymethyl ether of starch having a molecular weight in the range of 500,000 to 1,000,000 Daltons, and is commercially available as Explotab.RTM. and Primojel.RTM.. Sodium starch glycolate causes disintegration by rapid uptake of water, followed by rapid and enormous swelling. The advantage of using sodium starch glycolate as the superdisintegrant is that its effectiveness is not affected by the presence of hydrophobic excipients, such as lubricants, or by increased compression pressure. It is capable of swelling to 300 times its volume in water. Sodium starch glycolate is used as the preferred superdisintegrant in the present invention in an amount ranging from about 5% to about 50% by weight of the core, preferably from about 10% to about 40% by weight of the core, more preferably from about 15% to about 30% by weight of the core.

Hydroxyethyl cellulose is a non-ionic, water soluble polymer, which is a partially substituted poly(hydroxyethyl)ether of cellulose, and is available in different grades that vary in viscosity and degree of substitution. It is commercially available as Cellosize from Amerchol Corp., and Natrosol.RTM. from Aqualon. Preferably, hydroxyethyl cellulose having aqueous solution viscosity ranging from 9000 mPas to 30,000 mPas for a 2% w/v aqueous solution is used as the hydrophilic polymer in the present invention. It is used in an amount ranging from about 5% to about 50% by weight of the core, preferably from about 10% to about 40% by weight of the core, more preferably from about 15% to about 30% by weight of the core.

Hydroxypropyl methylcellulose (HPMC) is a partly O-methylated and O-(2-hydroxypropylated) cellulose, available in different grades that vary in viscosity. The molecular weight of HPMC ranges between 10,000 and 1,500,000. It is commercially available as Benecel MHPC, Methocel and Metolose. In one embodiment of the present invention, HPMC K4M grade is used as the swelling polymer in an amount ranging from about 5% to about 25% by weight of the core, more preferably from about 10% to about 15% by weight of the core.

In preferred embodiments the mixture of high viscosity grade hydroxyethyl cellulose and sodium starch glycolate is used as the highly swellable polymer, preferably in a weight ratio lying in the range of 1:9 to 9:1, more preferably 3:7 to 7:3 and still more preferably 4:6 to 6:4, of hydroxyethyl cellulose:sodium starch glycolate. The cores formed with this mixture are capable of swelling rapidly and achieving floatation while maintaining their physical integrity over prolonged periods of time.

The gas generating agent used in the core of the gastric retention controlled drug delivery system of the present invention may include a single component that generates gas upon contact with the gastric fluid, or may include a gas generating couple. Gas generating components that may be used in the present invention include carbonates such as calcium carbonate, bicarbonates such as sodium or potassium bicarbonate, sulfites such as sodium sulfite, sodium bisulfite, or sodium metabisulfite, and the like. These salts may be used alone or in combination with an acid source as a gas generating couple. The acid source may be an edible organic acid, a salt of an edible organic acid, or mixtures thereof. Examples of organic acids that may be used include citric acid, malic acid, succinic acid, tartaric acid, fumaric acid, maleic acid, ascorbic acid, glutamic acid, and their salts, and mixtures thereof. The gas generating agent is used in an amount ranging from about 1% to about 50% by weight of the core, more preferably from about 1% to about 15% by weight of the core. Sodium bicarbonate is used as the preferred gas generating agent.

The highly swellable polymer may further comprise an excipient that increases the rate of swelling of the delivery system. This excipient may be a water-soluble compound that induces osmosis, or a wicking agent such as microcrystalline cellulose, that promotes the influx of water into the system. Water-soluble compounds suitable for inducing osmosis, i.e. osmotic agents or osmogents, include all pharmaceutically acceptable and pharmacologically inert water-soluble compounds referred to in the pharmacopoeias such as United States Pharmacopoeia, as well as in Remington: The Science and Practice of Pharmacy. Pharmaceutically acceptable water-soluble salts of inorganic or organic acids, or non-ionic organic compounds with high water solubility, e.g. carbohydrates such as sugar, or amino acids, are generally preferred. The examples of agents used for inducing osmosis include inorganic salts such as magnesium chloride or magnesium sulfate, lithium, sodium or potassium chloride, lithium, sodium or potassium hydrogen phosphate, lithium, sodium or potassium dihydrogen phosphate, salts of organic acids such as sodium or potassium acetate, magnesium succinate, sodium benzoate, sodium citrate or sodium ascorbate; carbohydrates such as mannitol, sorbitol, arabinose, ribose, xylose, glucose, fructose, mannose, galactose, sucrose, maltose, lactose, raffinose; water-soluble amino acids such as glycine, leucine, alanine, or methionine; urea and the like, and mixtures thereof. In preferred embodiments, the core of the gastric retention controlled drug delivery system includes one or more osmotic agents that increase the rate of swelling of the system. Preferably, the osmotic agent is used in an amount ranging from about 0.5% to about 50% by weight of the core, more preferably from about 2% to about 40% by weight of the core.

The gastric retention controlled drug delivery system of the present invention may also include various pharmaceutically acceptable excipients, for example disintegrants such as starch, cellulose derivatives, gums, crosslinked polymers and the like; binders such as starch, gelatin, sugars, cellulose derivatives, polyvinyl pyrrolidone and the like; lubricants such as talc, magnesium stearate, colloidal silicon dioxide, polyethylene glycol, cellulose derivatives and the like; and mixtures thereof.

In preferred embodiments, hydroxypropyl methylcellulose (HPMC) is used as the binder. Preferably, HPMC K4M is used as the binder in an amount ranging from about 0.2% to about 5% by weight of the core, more preferably from about 0.2% to about 2% by weight of the core.

Examples of lubricants that may be used in the present invention include talc, magnesium stearate, calcium stearate, aluminum stearate, stearic acid, hydrogenated vegetable oils, colloidal silicon dioxide, polyethylene glycol, cellulose derivatives such as carboxyalkyl cellulose and its alkali salts, or mixtures thereof. In preferred embodiments, the lubricant used is a mixture of silicified microcrystalline cellulose, talc and polyethylene glycol. Silicified microcrystalline cellulose is a synergistic, intimate physical mixture of microcrystalline cellulose and colloidal silicon dioxide, having a particle size in the range of 20 to 200 .mu.m, and generally contains 2% by weight of colloidal silicon dioxide. It is commercially available as Prosolv.RTM. SMCC, and has an improved compaction property as compared to microcrystalline cellulose. The polyethylene glycol (PEG) used is PEG 8000. The mixture is used as the lubricant in an amount ranging from about 0.5% to about 40% by weight of the core, preferably from about 5% to about 30% by weight of the core, more preferably from about 10% to about 25% by weight of the core.

The core of the gastric retention controlled drug delivery system is surrounded by a rapidly releasing coat composition comprising the same drug as in the core, and pharmaceutically acceptable excipients. In a preferred embodiment of the present invention, the coat composition comprises baclofen and pharmaceutically acceptable excipients, such as film forming agents, plasticisers and the like. The film forming agents are selected from a group comprising cellulose ethers and esters such as methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose (HPMC); acrylic acid polymers such as methacrylate and methyl methacrylate copolymers, and the like, and mixtures thereof. In preferred embodiments hydroxypropyl methylcellulose is used as the film forming agent in an amount ranging from about 0.5% to about 5% by weight of the core, preferably from about 1% to about 3% by weight of the core. The rapidly releasing composition may further contain one or more plasticisers selected from a group comprising glycerin, propylene glycol, polyethylene glycols, acetylated monoglyceride, citrate esters such as triethyl citrate, and phthalate esters such as diethyl phthalate. In preferred embodiments propylene glycol is used as the plasticiser. Alternatively, hydroxypropyl methylcellulose coating solution, commercially available as Opadry.RTM. II from Colorcon, may be mixed with the drug and used to coat the controlled release cores.

The manufacture of coated tablets may be performed in two steps. In the first manufacturing step the core composition is added to the die cavity at a first compression station, compressed and ejected with the aid of a lower punch. The second step consists of applying a coat on the core by conventional methods such as spray coating or compression coating. Spray coating comprises exposing the surfaces of the core by rolling it in a suitable coating vessel or by fluidizing them in a fluidizing equipment; and applying coating compositions containing drug and coating polymers. The drug is incorporated either in the same composition containing the coating polymer in a liquid vehicle or is layered as a powder. Compression coating comprises filling the coating composition for the lower half of the tablet into the die at a second compression station, transfer of the core from the first compression station to the second compression station and its placement in the center of the coating composition already filled into the die, filling of the upper half of the coating composition into the die, a compression phase to form the coated tablet, and an ejection phase that serves to remove the compression coated tablet from the die with the aid of the lower punch.

The gastric retention controlled drug delivery system of the present invention rapidly swells while maintaining its physical integrity in gastrointestinal fluids for prolonged periods. A low density is achieved by entrapment of the gas generated by the gas generating agent such that the system floats in gastric fluids. The swelling and gas entrapment can occur rapidly such that the system is capable of achieving floatation in a dissolution bath containing 0.1N HCl in 15 minutes, preferably in less than 10 minutes.
 

Claim 1 of 1 Claim

1. An oral controlled drug delivery system for once-a-day therapy comprising baclofen and release rate controlling excipients, wherein the said system is adapted to release baclofen in a controlled manner so as to provide control over the plasma levels, such that the plasma levels of baclofen are within a desirable range over a 24-hour period for said once-a-day therapy.

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