floating drug delivery systems

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CONTENTS Introduction Basic gastro intestinal tract physiology Mechanism of floating systems Factors affecting floating Advantages and disadvantages of FDDS Floating drug delivery systems Drugs and polymers used in FDDS Commercial gastro retentive formulations Evaluation Conclusion 2

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Introduction: Floating drugs are gastro retentive systems which can remain in gastric region for several hours and hence significantly prolong the gastric residence time of drugs. FDDS helps in the local drug delivery to the stomach & proximal small intestines. FDDS enhances GRT and shows better control of fluctuations in plasma drug concentration. FDDS helps to provide better availability of new products with new therapeutic possibilities & substantial benefits for patients.. 3

Why is FDDS needed?:

Why is FDDS needed? The gastric emptying time in humans which normally averages 2-3hr through the major absorption zone (stomach & upper part of intestine) can result in incomplete drug release from the drug delivery system leading to reduced efficacy of administered dose. Lower dosing and less side effects. Beneficial in the treatment of gastric diseases. Suitable dosage forms for the drugs those are primarily absorbed in the stomach . 4

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BASIC GASTRO INTESTINAL TRACT PHYSIOLOGY Stomach: Fundus Body Antrum or pylorus Migrating myloelectric cycle: (MMC) 5

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6 MECHANISM OF FLOATING SYSTEMS FDDS have a bulk density less than gastric fluids and so remain buoyant in the stomach without affecting the gastric emptying rate for a prolonged period of time. Mechanism of floating systems, GF= Gastric fluid F = F buoyancy - F gravity = (Df - Ds) gv--- (1) Where, F= total vertical force, Df = fluid density Ds = object density, v = volume and g = acceleration due to gravity

Factors affecting floating time:

Factors affecting floating time Density, size & shape of dosage form Single or multiple unit formulation Fed or unfed state Nature of meal Frequency of feed Age & gender posture Bilogical factors 7


ADVANTAGES OF FDDS Principle of FDDS can be used for any class of medicament. More advantageous for drugs absorbed through stomach e.g. treatment of peptic ulcer disease e.g. antacids. Drugs that have absorption windows in the upper part of the small intestine. They will gradually empty in solution form to the site of absorption. Certain types of drugs can benefit from using FDDS. These include. a) Drugs acting locally in the stomach. b) Drugs those are primarily absorbed in the Stomach. c) Drugs those are poorly soluble at an alkaline pH. d) Drugs with a narrow window of absorption. e) Drugs absorbed rapidly from the GI tract. f) Drugs those degrade in the colon.


DISADVANTAGES OF FDDS There are certain situations where gastric retention is not desirable. Aspirin and non steroidal anti-inflammatory drugs are known to cause gastric lesions, and slow release of such drugs in the stomach is unwanted. Thus, drugs that may irritate the stomach lining or are unstable in its acidic environment should not be formulated in gastro retentive systems. Furthermore, other drugs, such as isosorbide dinitrate, that are absorbed equally well throughout the GI tract, drugs undergoing first pass metabolism will not benefit from incorporation into a gastric retention system. It requires sufficient high level of fluids in the stomach for the drug delivery to float. The dosage form should be administered with a full glass of water (200-250 ml). 9

Classification of fdds :

Classification of fdds Based on the mechanism of buoyancy FDDS can be classified into A . Single Unit Floating Dosage Systems a) Non-effervescent Systems b) Effervescent Systems (Gas-generating Systems) B . Multiple Unit Floating Dosage Systems a) Non-effervescent Systems b) Effervescent Systems (Gas-generating Systems) c) Raft Forming Systems d) Hollow Microspheres 10

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hydrodynamic balanced systems (hbs) Sheth and Tossounian first designated this ‘hydrodynamically balanced system’. Such a system contains drug with gel-forming hydrocolloids meant to remain buoyant on the stomach content. 11 The gelatinous polymer barrier formation results from hydrophilic polymer swelling. Drug is released by diffusion and erosion of the gel barrier.


FLOATATION CHAMBER Fluid- filled floating chamber which includes incorporation of a gas-filled floatation chamber into a micro porous component that houses a drug reservoir. 12 Gas filled floatation chamber

Effervescent floating dosage forms :

Effervescent floating dosage forms These are matrix type of systems prepared with the help of swellable polymers such as methylcellulose and chitosan and various effervescent compounds, e.g, sodium bicarbonate, tartaric acid, and citric acid. They are formulated in such a way that when in contact with the acidic gastric contents, co2 is liberated and gets entrapped in swollen hydrocolloids, which provide buoyancy to the dosage forms. 13 Gas generating system: schematic monolayer drug delivery system

Alginate beads :

Alginate beads Alginates have received much attention in the development of multiple unit systems. Alginates are nontoxic, biodegradable linear copolymers composed of L glucuronic and L-mannuronic acid residues. Multiple unit floating dosage forms have been developed from freeze dried calcium alginate. Spherical beads of approximately 2.5 mm in diameter can be prepared by dropping a sodium alginate solution in to aqueous solutions of calcium chloride, causing precipitation of calcium alginate. The beads are then separated snap and frozen in liquid nitrogen, and freeze dried at -40°C for 24 hours, leading to the formation of porous system, which can maintain a floating force over 12 hours. drugs encapsulated with alginate beads

Raft forming systems:

Raft forming systems On contact with Gastric fluid A gel-forming solution (e.g. sodium alginate solution containing carbonates or bicarbonates) swells and forms a viscous cohesive gel containing entrapped CO2 bubbles. Which forms Raft layer on top of gastric fluid which releases drug slowly in stomach. Such formulation typically contain antacids such as aluminium hydroxide or calcium carbonate to reduce gastric acidity. They are often used for gastro­­- esophageal reflux treatment as with Liquid Gaviscon (GSK). Figure : Barrier formed by a raft-forming


HOLLOW MICRO SPHERES (MICRO BALLOONS) Hollow microspheres are considered as one of the most promising buoyant systems , as they possess the unique advantages of multiple unit systems as well as better floating properties, because of central hollow space inside the microsphere. The general techniques involved in their preparation include simple solvent evaporation, and solvent diffusion and evaporation. 16 Figure: Micro balloons

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Floating microspheres – Aspirin, Griseofulvin,m p- nitroaniline , Ibuprofen, Ketoprofen , Piroxicam , Verapamil , Cholestyramine , Theophylline , Nifedipine , Nicardipine , Dipyridamol , Tranilast and Terfinadine Floating granules - Diclofenac sodium, Indomethacin and Prednisolone . Films – Cinnarizine , Albendazole Floating tablets and Pills - Acetaminophen, Acetylsalicylic acid, Ampicillin , Amoxycillin trihydrate, Atenolol , Fluorouracil, Isosorbide mononitrate , Para- aminobenzoic acid, Piretanide , Theophylline , Verapamil hydrochloride, Chlorpheniramine maleate, Aspirin, Calcium Carbonate, Fluorouracil, Prednisolone , Sotalol , pentoxyfilline and Diltiazem HCl . Floating Capsules - Chlordiazepoxide hydrogen chloride, Diazepam, Furosemide , Misoprostol , L- Dopa , Benserazide , Ursodeoxycholic acid and Pepstatin , and Propranolol . Drugs Used In the Formulations of FDDS

polymers& other ingredients used in formulation of FDDS: :

polymers& other ingredients used in formulation of FDDS: 18 Hydrocolloids (20%-75%): hydrophilic gums, modified cellulose derivatives. Eg . Acacia, pectin, Chitosan,agar , casein, bentonite , veegum , HPMC(K4M, K100M and K15M), Gellan gum( Gelrite ®), Sodium CMC, MC, HPC Inert fatty materials(5%-75%): Eg . Beeswax, fatty acids, long chain fatty alcohols. Effervescent agents: Sodium bicarbonate, citric acid, tartaric acid, Di-SGC (Di-Sodium Glycine Carbonate, CG ( Citroglycine ) Release rate accelerants(5%-60%): eg lactose, mannitol Release rate retardants (5%-60%): eg Dicalcium phosphate, talc, magnesium stearate Buoyancy increasing agents (up to 80%): ethyl cellulose Low density material : poly propylene flow powder.


EVALUATION OF FDDS A. Invitro methods Floating lag time & floating time Dissolution study Resultant weight test B. Invivo methods X ray method Gamma- scintigraphy Gastroscopy Ultra sonography 19

Conclusion :

Conclusion FDDS promises to be a potential approach for gastric retention. Dosage forms with a prolonged GRT will bring about new and important therapeutic options. The currently available polymer-mediated Non effervescent and effervescent FDDS, designed on the basis of delayed gastric emptying and buoyancy principles, appear to be a very much effective approach to the modulation of controlled oral drug delivery. Due to the complexity of pharmacokinetic and pharmaco dynamic parameters, in vivo studies are required to establish the optimal dosage form for a specific drug. A large number of companies are focusing toward commercializing this technique. 20

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S.P. Vyas, R.K. Khar ; controlled Drug Delivery N.K.JAIN; Progress in controlled and novel drug delivery systems. Whitehead H,Fell j.t & collet j.h development of gastro retentive dosage form. Shiv kumar H.G vishakanthe D. Floating controlled drug delivery systems Timmermanns j. and Moes A.(1990).How well do floting dosage forms float? Stops F.,Fell J.T., Collet J.H., L.G. Floating dosage forms to prolong gastroretention– the characterisation of calcium alginate beads. 21

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