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CONTROLLED RELEASE TABLET DOSAGE FORM

CONTROLLED RELEASE TABLET DOSAGE FORM. controlled-release tablets. tablets are designed to release the drug slowly after ingestion. Advantages: Patient compliance is improved, since only one or two tablets need to be taken daily

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CONTROLLED RELEASE TABLET DOSAGE FORM

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  1. CONTROLLED RELEASE TABLET DOSAGE FORM

  2. controlled-release tablets tablets are designed to release the drug slowly after ingestion. Advantages: Patient compliance is improved, since only one or two tablets need to be taken daily Reduces the severity or frequency of side effects. as a controlled-release Aspirin, has been shown to produce less gastric bleeding A controlled -release tablet produces a more constant blood level of drug than repeated doses of a conventional tablet e.gaminophylline

  3. Disadvantages: The cost of controlled release tablets is more per unit dose than conventional dosage forms. Some drugs, such as riboflavin and ferrous sulphate, are more efficiently absorbed in particular regions of the gastrointestinal tract and therefore controlled-release tablets are not very useful, because they release the drug throughout the intestinal tract. Accidental poisoning with poor formulated controlled-release where all the drug being released at once. dosage forms does present special treatment

  4. The slow release of the drug into the gastrointestinal tract, and slow clearance of drug from the body result in problems . E.g controlled -release tablets of potassium Chloride have been known to cause ulceration due to delayed gastrointestinal transit time. The physical size of the dosage form may present problems. Some patients have difficulty in swallowing a 600-650 mg controlled -release tablet and it is often difficult to formulate the tablets.

  5. FORMULATION FACTORS AFFECTING THE RELEASE OF A DRUG FROM TABLETS The effective surface area of drug release The dissolution rate of a drug is directly related to the surface area exposed to the dissolution media. Effect of binding agents Binding agents are incorporated into tablets to improve the flowability of the drug & to enhance compressibility. the rate of dissolution of the binder in water can determine the release rate of drug from the tablet.

  6. tablets containing water soluble binders (hydrolysed gelatin and PVP) had rapid dissolution rates whereas tablets formulated with starch paste, Methyl hydroxy ethyl cellulose (MHEC) hadslow and incomplete disintegration rates. Effect of disintegrants Disintegrants facilitate the rapid entrance of water into the centre of the tablet or capsule ; result in rapid drug release. Tablets containing sodium starch glycollate were superior in dissolution properties from similar tablets containing microcrystalline cellulose and PVP .This effect is due to the high swelling capacity of these disintegrants.

  7. Effect Of Lubricants • lubricating agent prevent the dosage form sticking to the processing machinery. • The hydrophilic lubricant as sodium lauryl sulphate allowed the drug to dissolve more rapidly • The hydrophobic lubricant magnesium stearate produced a decrease in dissolution rate.

  8. Effect of diluents • The calcium salts as calciumorthophospahte and calcium hydrogen orthophosphate promote the rapid disintegration of the tablets and therefore give quick drug release. • Sorbitol , lactose markedly decrease the release rate because it dissolves very slowly and therefore release of the drug occurs by erosion. • Effect of granule size • Granule size was not a critical factor affecting the pharmaceutical properties of the tablets.

  9. Formulation of controlled release tablets • Controlled -release tablets consist of two parts: • - An immediately available dose • A sustaining part, containing the therapeutic dose, for • prolonged blood drug levels. • The immediately available dose is incorporated in the tablet coating with the sustaining portion.

  10. Methods of achieving controlled release • Diffusion-controlled release • The rate at which diffusion occurs is depend upon: • - The surface area - The diffusional pathway • - The drug concentration gradient • The diffusion coefficient of the system. • Diffusion-controlled release produced by: • formulating the drug in an insoluble matrix such as methylcellulose or insoluble plastic inert substances such as methyl methacrylate.

  11. The core (drug) and the matrix tableted together by compression. Coating can be applied using a coating pan or air-suspension technique. • The gastro-intesinal fluids penetrate the matrix and drug diffuses out of the matrix and absorbed. • With coated matrix tablets the initial dose is normally placed in the coat of the tablet. • In non-coated systems the initial dose is normally tableted with the matrix granulation.

  12. Dissolution-controlled release • Drugs with poor dissolution rates are prolonged release • water-soluble drugs it is possible to incorporate a water insoluble carrier into the tablet formulation to reduce dissolution. • Prolonged drug relase can be achieved by avoid the use of disintegrating agent in the tablet formulation.

  13. these products formulated by: • coating individual drug particles or granules with a slowly soluble coating material such as polyethylene glycol of various thickness. • The time required for dissolution of the coat is proportional to the coating thickness. • The coated particles can be compressed directly into tablets. • A pulsed dosing effect can be also obtained by utilizing different coat types.

  14. Release controlled by ion exchange • Ion exchange materials are water-insoluble resine containing salt-forming groups. • Either anionic or cationic groups can be used to produce the desired ion exchange resin. • The drug-charged resin is prepared by: • mixing the resin with drug solution, then washing to remove contaminant ions and then dried to form beads or particles which are tableted. • Drug release is achieved in the presence of a high concentration of charged ions in the gastrointestinal tract; the drug molecule is exchanged and diffused out of the resin to the gastrointestinal fluids.

  15. Ion-exchange resine (styrene di-vinyl benzene copolymer) Ananionic groupCataionic group COOH, +cataionc drug +Anaionic drug (Atropin)(Deltiazem HCL) Resin-SO3- D+ Resin-N(CH3) 3+ D- GI (HCL) GI (HCL) Resin-SO3- H + + D Resin-N(CH3) 3+ CL- + D

  16. The main disadvantage: • The drug release depend only on the ionic environment of the resin not on pH or enzyme content at the absorption site. • The ionic content of the gastrointestinal tract varies with diet and water content, and therefore variable drug release results.

  17. Release controlled by osmotic pressure • A semipermeable membrane is placed around a tablet or drug particle which allows transport of water into the centre of the tablet by osmosis. • As a result of increased internal pressure, drug solution is then pumped out of the tablet through a small hole in the tablet coating is bored with the use of a laser beam. .

  18. Advantages : The delivery rate is constant where that excess drug present inside the tablet rapidly declines to zero once the concentration drops to below saturation. the system delivers drug based on osmotic pressure, independent of stirring rate and environment pH.

  19. Tablet Coating as a Technique for controlling release Types Of Tablet Coating • There are three types in common use: • Sugar coating • Film coating • Press coating (compression coating). • Of these the most important are sugar coating and film coating.

  20. Reasons for coating tablets • 1. Protection of ingredients from the environment, light and moisture. • 2 .For taste masking that aid patient compliance with • dosage schemes. • 3. Coloured coatings aid in the rapid identification of • producttablets with differing appearance. • 4. Coating confers an added mechanical strength to the • tablet core. • 5. Functional film coatings are used to impart enteric or • controlled release properties to the coated tablet.

  21. Enteric coating This technique is used to protect the tablet core from disintegration in the acid environment of the stomach for one or more of the following reasons: 1. Prevention of acid attack on active constituents unstable at low pH 2. To protect the stomach from the irritant effect of certain drugs 3. To facilitate absorption a drug preferentially absorbed distally to the stomach.

  22. The following polymers are commonly used for the purposes of enteric coating: • Cellulose acetate phthalate • Polyvinyl acetate phthalate • Acrylates (Eudragit L100). • Due to the presence of free carboxylic acid groups on the polymer backbone, they exhibit a differential pH solubility profile. These are almost insoluble in aqueous media at low pH but as the pH rises they experience a sharp, well defined increase in solubility at a specific pH, e.g. pH 5.2 for cellulose acetate phthalate.

  23. Enteric coating is possible using both sugar and film coating techniques. Enteric sugar coating The sealing coat is modified to comprise one of the enteric polymers in sufficient quantity The subcoating and subsequent coating steps are then as for conventional sugar coating. Enteric film coating Sufficient weight of enteric polymer has to be used to ensure an efficient enteric effect. This is normally two or three times that required for a simple film coating.

  24. Press coatings The polymers used in coating include: 1. Modified acrylates 2. Water-insoluble celluloses e.g. ethyl cellulose. Press coatings

  25. Tablets Used in the Oral Cavity • Chewable Tablets • Advantages of the chewable tablet • provide a unit dosage form easily administered to infants and children or to the elderly, who may have difficulty swallowing a tablet intact. E.g Many antacid tablet products are of the chewable type.

  26. The chewable tablet offers two major advantages to the delivery of a solid antacid dosage form: 1) The dose of most antacids is large, so that the typical antacid tablet would be too large to swallow. 2) As the activity of an antacid is related to its particle size. If the tablet is chewed prior to swallowing, better acid neutralization may be possible from a given antacid dose. Disadvantages : Bitter or foul-tasting drugs are not good candidates for this type of tablet, and this fact restricts the use of the chewable tablet dosage form.

  27. Buccal and Sublingual Tablets Buccal tablet are intended to be held between the cheek and teeth or in the cheek pouch Sublingual tablets beneath the tongue

  28. Advantages: The gastric environment, where decomposition may be extensive (for certain steroids and hormones), may be avoided for drugs that are well absorbed in the mouth. A more rapid onset of drug action occurs than for tablets that are swallowed (an advantage with vasodilators given by this route). Avoids first-pass metabolism formulated with tasteless excipients, which do not stimulate salivation. This reduces the fraction of the drug that is swallowed rather than being absorbed through the oral mucosa. these tablets designed not to disintegrate but to slowly dissolve, typically over a 15 to 30-min period, to provide effective absorption.

  29. Lozenges and Troches Lozengesare originally termed pastilles, but are more commonly called cough drops. They are usually made with the drug incorporated in a flavored hard-candy sugar base. Lozenges may be made by compression but are usually formed by fusion or by a candy-molding process. Troches are manufactured by compression as other tablets.

  30. Advantages : they are exert a local effect in the mouth or throat. These tablet forms are commonly used to treat sore throat or to control coughing in the common cold. They may contain local anesthetics, various antiseptic and antibacterial agents, demulcents, astringents, and antitussives. These two classes of tablets are designed not to disintegrate in the mouth but to dissolve or slowly erode over a period of perhaps 30 min or less.

  31. Dental Cones designed to be placed in the empty socket remaining following a tooth extraction. The usual vehicle of these tablets is sodium bicarbonate, sodium chloride, or an amino acid.

  32. Advantages : prevent the multiplication of bacteria in the socket by employing a slow-releasing antibacterial compound, or to reduce bleeding by containing an astringent or coagulant. The tablet formulated to dissolve or erode slowly in the presence of a small volume of serum or fluid, over a 20- to 40-min period, when loosely packed in the extraction site.

  33. Tablets Administered by Other Routes Implantation Tablets Implantation or depot tablets are designed for subcutaneous implantation in animals or man for the administration of growth hormones to food-producing animals.

  34. Advantages: provide prolonged drug effects, ranging from one month to a year. provide constant a drug delivery release rate as possible. Disadvantages: this dosage form has achieved little use in humans. need for a surgical technique to discontinue therapy cause tissue toxicity problems in the area of the implantation site.

  35. Vaginal Tablets Vaginal tablets or inserts are designed to undergo slow dissolution and drug release in the vaginal cavity. The tablets are typically ovoid or pear-shaped to facilitate retention in the vagina. The tablets designed to be compatible with some type of plastic tube inserter, which is usually employed to place the tablet in the upper region of the vaginal tract.

  36. Advantages: used to release antibacterial agents, antiseptics, or astringents to treat vaginal infections, or possibly to release steroids for systemic absorption. The vehicle of these tablets is typically a slowly soluble material similar to agents described for the preparation of buccal tablets.

  37. Tablets Used to Prepare Solutions • Effervescent Tablets • The tablets are typically prepared by compressing the active ingredients with mixtures of organic acids-such as citric acid or tartaric acid-and sodium bicarbonate. • When such a tablet is dropped into a glass of water, a chemical reaction is initiated between the acid and the sodium bicarbonate to form the sodium salt of the acid, and to produce carbon dioxide and water completed within one minute or less.

  38. The advantage it provides a means of preparing a solution containing an accurate drug dose As in the case of effervescent aspirin tablet has a pH of about 8. If pH of the gastric contents raise to neutral or near-netural pH, the aspirin remains in solution and is rapidly available upon emptying from the stomach, that this form of aspirin is less irritating to the stomach mucosa. having the capability of producing clear solutions, also produce a pleasantly flavored carbonated drink, which assists in masking the taste of certain drugs.

  39. The disadvantage is the difficulty of producing a chemically stable product where the moisture in the air during product preparation may be adequate to initiate effervescent reactivity. During the course of the reaction, water is liberated from the bicarbonate, which autocatalyzes the reaction. Need adequate protection of effervescent tablets in the hands of the consumer where the moisture to which tablets are exposed after opening the container result in a rapid loss of product quality.

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