Tablets - l Pharmaceutical Technology ll Presented by Dr. Md. Harun Ar Rashid Head Department of Pharmacy NUB
“A tablet is a solid single unit dosage form containing one or more active ingredients with or without auxillary substances, prepared by compression and molding.” • Intended mainly for oral administration • Most commonly are disk shaped with convex surfaces • Available in special shape like round, oval, oblong, cylindrical, square, triangular • Widely used solid dosage form because they offer a number of advantages to the patient, prescriber, manufacturer and manufacturing pharmacist
-They should be accurate and uniform in weight -The drugs should be uniformly distributed throughout the tablets -The size and shape should be reasonable for easy administration -The tablets should not be too hard that it may not disintegrate in the Stomach -There should not be any incompatibilities -They should be chemically and physically stable during storage . Cont. Essential qualities of a good Tablets
Essential qualities of a good Tablets - They should not break during transportation or crumble in the hands of the patient - They should be attractive in appearances - There should not be any manufacturing defects like cracking, chipping discolouration - After disintegration it should release the drug readily - They should be easy and economical in production.
Advantages - Offer greatest dose precision and the least content variability - easy to be swallowed or administered - easy to handle and carry by the patient - economical, manufacturing cost are low, manufacturing speed is quite high - most stable with respect to physical, chemical and microbiological attributes - Bitter, unpleasant taste and nauseous odour of medicaments can be easily masked by administering in the form of coated tablet -
Advantage (Continued) - product identification is probably the easiest because of the variety of shapes and colours of tablets that are possible - the lightest and the more compact of all dosage forms - the easiest and the cheapest to pack and transport - don’t require any measurement of dose
Advantage (continued) • Can be divided into halves, quarters by drawing lines during manufacture to facilitate breakage whenever a fractional dose is required • Lend themselves to certain special release profile such as enteric or delayed release products • Attractive and elegant in appearance
in storage, dispensing, and control • In Summary Solid Dosage Forms, Most Notably Tablets Provide Advantages convenience of use To the pharmacist To the patient of product identification, dosage accuracy and precision, improved control and more reliable therapy To the physician cheaper due to mass production and easier to manufacture, simplicity, economy, stability, and convenience To the manufacturer
Disadvantages • Amorphous and Low density drugs are difficult to compress. • High doses are difficult to formulate as tablet dosage form. • Bitter tasting and objectionable odour drugs require special treatment like coating or encapsulation and increase the cost. • Drugs that are sensitive to oxygen or atmospheric moisture may also require special coating as well as costly packaging which may increase the overall cost of finished product
Disadvantage (Continued) • Drugs with poor wetting and slow dissolution properties are difficult to convert into tablets which will provide full drug bioavailability. • Drugs that are liquid at room temperature can not be formulated in tablet dosage form • A major disadvantage with respect to convenience of patients is the difficulty of swallowing specially by children and ill patients
Different Types of Tablets Classified into a number of categories, based on their • -Their methods of manufacture • -Type of drug delivery system • - Formulation and Functions • **Not all classes are entirely different but mostly overlap each other, such as, - Chewable and Effervescent tablets are single layered uncoated tablets
Classification (continued) Table1. Classified based on the method of manufacture and type of drug deliver system (A) Tablets ingested orally: -- Compressed tablet, e.g. Paracetamol tablet • Multiple compressed tablet • Delayed release tablet, e.g. Enteric coated Bisacodyl tablet • Sugar coated tablet, e.g. Multivitamin tablet • Film coated tablet, e.g. Metronidazole tablet • Chewable tablet, e.g. Antacid
Classification (continued) • (B) Tablets used in oral cavity : • Buccal tablet, e.g. Vitamin-c tablet • Sublingual tablet, e.g. Vicks Menthol tablet • Troches or lozenges • Dental cone (C) Tablets administered by other routes: - Implantation tablet - Suppositories or Inserts, e.g. Clotrimazole tablet
(D) Tablets used to prepare solution: • Effervescent tablet, e.g. Dispirin tablet (Aspirin) • Dispensing tablet, e.g. Enzyme tablet (Digiplex) • Hypodermic tablet • Tablet triturates e.g. Enzyme tablet (Digiplex)
Standard compressed tablet - Prepared by single compression - employ any of the three basic methods of manufactures: wet granulation, dry granulation and direct compression. - most of the tablets containing drugs intended to exert a local effect in the GIT are of this type (antacids and adsorbents) - Other drugs in this group are intended to produce systemic effect. - Tablets break up and particle deaggregation are important
Multiple compressed Tablet Tablets of this category are usually prepared for one of the two reasons:- a. to separate physically or chemically incompatible ingredients b. to produce repeat action or prolonged action products - layered tablets consist of parallel layers obtained by successive compression of particles of different comp. - press coated or dry coated tablets are prepared by compressing a layer of granules over a previously compressed tablets. (manesty drycota).
The layered tablets are rapid, surface contact between layers is lessened, production is simpler so preferred. • The shortcomings of this category of dosage form for repeat – action products is that its performance is highly dependant on gastric empting. XX, If the second layer or core tablet quickly leaves the stomach following release of the initial fast release dose, an entirely different blood level profile results than if there is a several hour or longer delay before the second fraction is emptied. - this is the reason that relatively few repeat –action or controlled release products using this approach are marketed.
Repeat action tablets • In addition to compressed tablets, sugar coated tablet may also employed. • The core tablet is usually coated with shellac or an enteric polymer so that it will not release the loading drug in the stomach. • The second dose of drug is then added in the sugar coating.
Delayed action and enteric coated tablet • The delay action tablet dosage form is intended to release a drug after some time delay or after the tablet has passed through the part of GI tract into another. • The enteric coated tablet is the most common example • All enteric coated tablets are a type of delayed action tablet but not all delayed action tablet are enteric • Cellulose acetate phthalate, Polyvinyl acetate phthalate, Hydroxypropyl methyl cellulose phthate have come into use for this . • These polymers being acid esters, are insoluble in gastric media that have a pH up to about 4.
Chewable tablets • Are compressed tablets which have a smooth, rapid disintegration when chewed or allowed to dissolve in the mouth and contains a creamy base of a specially flavored and colored mannitol. • Two major advantages are, a.The dose of most antacid is large so that the typical antacid tablet would be too large to swallow b.The activity of antacid is related to its particle size. If the tablet is chewed prior to swallowing better acid neutralizing may be possible from a given antacid dose
Xylitol may be used in the preparation of sugar-free chewable tablets. Xylitol is sweeter than mannitol. • lubricant and binders must not affect the texture or desired hardness of the tablet • colorant and tart or fruity flavorants are commonly employed to enhance the appeal of the tablets • Examples of chewable tablets: Calcium carbonate - antacids; Erythromycin - antibiotics; Didanosine - anti-infectives; Carbamazepine - anticonvulsants; Isosorbide dinitrate - vasodilator; Acetaminophen - analgesics; various vitamins and cold-allergy combination tablet
Tablets used in the oral cavity • This type of tablet are placed in the mouth but not swallowed. *Buccal and sublingual tablets • These tablets , though not swallowed, are intended to provide systemic drug action. • These are small, flat, usually oval dosage forms to be inserted in the buccal , or cheek, pouch (buccal tablet) or beneath the tongue (sublingual tablets). • The drug is absorbed directly through the oral mucosa, thereby avoiding the acid and enzymatic environment of the stomach and the drug metabolizing enzymes of the liver.
Drugs are commonly administered by the oral mucosal route: the vasodilator glyceryl trinitrate: Steroids, such as methyl testosterone, testosterone propionate, estradiol: and, possibly, some miscellaneous hormones and drugs, such as pancreatic lipotropic hormone factors,hesperidin, and nicotinic acid. • Drugs that may be absorbed via the oral mucosa have several possible advantages: (1) Avoidance of the gastric environment and the decomposition it may produce with some steroids and hormone (2) a more rapid onset of drug action than occurs with tablets which are swallowed (3) Reduction of nausea, with drugs that produce this effect when swallowed (4) More efficient drug utilization (lower dose), owing to avoidance of inactivation by liver drug metabolising enzymes.
. Drugs absorbed from the gastrointestinal tract enter the mesenteric circulation which feeds directly into the liver via the portal vein. Drug absorption from the oral cavity involves drug diffusion into the blood and lymph canals through the sublingual or oral mucosa. Blood is supplied to this region via the external carotid artery and is returned via the jugular veins into the general circulation rather than going directly to the portal vein. Many steroids are either relatively or totally inert if ingested owing to inactivation by liver enzymes. This loss of potency can be circumvented by other modes of administration such as intramuscular injection, implantation of tablets, use of vaginal suppositories, or absorption through the oral mucosa. The latter method, in many instances, is preferable. • Since most drugs, including weakly acidic drug moieties, are probably absorbed primarily in the upper small intestine. The tablet must disintegrate, the drug dissolve, and the stomach empty at least partially before drug absorption begin. Therefore , a time lag of 30 minutes or more (corresponding to the time required for the drug to be dissolved and leave the stomach) is typical before a drug effect is exerted after swallowing a tablet. on the other hand , total drug absorption typically occurs within 30 minutes after buccal or sublingual tablets have been administered and onset of action is common with vasodilator drugs.. • Buccal and sublingual tablets are designed not to disintegrate but to dissolve slowly over a 15 to 30 minute period. The tablet composition should not promote salivation, which would result in swallowing dissolved drug, thereby circumventing the purpose of the buccal or sublingual tablets.
Dental cones • The cones may contain an antibiotic or antiseptic typically in a filler of Sodium bicarbonate, sodium chloride, amino acid, or lactose. • The cones are formulated and compression so that a small volume of serum or fluid will cause disintegration and dissolution in 20 to 30 minutes.
Tablets administered by other routes Implantation tablets • This is also known as pellets, are small sterile tablets, cylindrical shaped and usually not over 8 mm. in length, for subcutaneous implantation in man or animals to provide very prolonged drug effects – for 3 to 6 months or longer. • In man, use of this dosage form is limited to very potent drugs which are not orally absorbed, notably steroids such as Desoxycorticosterone, testosterone, or estradiol. • The major advantage of the dosage form is to provide continuous therapy over many months without the need for repeated parenteral dosing. Over a long periods of time this form of therapy can be most economical. Also, it may provide the most even and uniform hormone therapy.
Implantation tablets The immediate and potential disadvantage of implantation therapy are: • - the surgical technique which may be required for implantation • - the difficulty of maintaining a constant drug release rate as the pellet changes geometry with dissolution • - the possibility of a histopathological (tissue toxicity) reaction against the implanted ‘foreign body’ • -the need to employ a surgical technique to terminate the therapy should such termination become necessary
Vaginal tablets • Also called inserts, are generally ovoid or pear shaped made by compression and intended to undergo dissolution and drug release in the vaginal cavity. • The tablets are usually used in the treatment of trichomonas vaginitis and • contain organic iodine (iodochlor or iodohydroxyquinoline compounds) or other antiseptics, astringents, or steroids in a soluble base of lactose or sodium biocarbonate.
Effervescent tablets • These tablet produce effervescence when added to cold water. Effervescence which is usually carbon dioxide is generated due to chemical reaction which take place between a Bicarbonate and an acid (citric acid and Tataric acid) • The effervescence causes rapid disintegration of the tablet and also increases the palatability ।