`
`VOLUME # 121
`
`5
`contents
`pH 1-3
`
`(a
`UEP
`RUM UTTATE T(E
`
`MYLAN EXHIBIT 1043
`
`CTOlIC=IOM ONY
`eG)Scldanse oretCol
`* Christopher T. Rhodes
`
`MYLAN EXHIBIT 1043
`
`
`
`Modern
`Pharmaceutics
`
`Fourth Edition, Revised and Expanded
`
`edited by
`Gilbert S. Banker
`University of Iowa
`Iowa City, Iowa
`
`Christopher T. Rhodes
`University of Rhode Island
`Kingston, Rhode Island
`
`t
`
`MAI\ C El
`
`•
`
`MARCEL D EKKER, l NC,
`
`0£KKEII
`
`N EW YORK . BASEL
`
`
`
`ISBN: 0-8247-0674-9
`
`This book is printed on acid-free paper.
`
`Headquarters
`Marcel Dekker, Inc.
`270 Madison Avenue, New York, NY 10016
`tel: 212-696-9000; fax: 212-685-4540
`
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`tel: 41-61-261-8482; fax: 41-61-261-8896
`
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`
`The publisher offers discounts on this book when ordered in bulk quantities. For more information, write to Special Sales/
`Professional Marketing at the headquarters address above.
`
`Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
`Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical,
`including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in
`writing from the publisher.
`
`Current printing (last digit):
`10 9 8 7 6 5 4 3 2
`
`PRINTED IN THE UNITED STATES OF AMERICA
`
`
`
`Contents
`
`Preface
`Contributors
`
`1. Drug Products: Their Role in the Treatment of Disease, Their Quality, and
`Their Status and Future as Drug-Delivery Systems
`Gilbert S. Banker
`
`2. Principles of Drug Absorption
`Michael M ayersohn
`
`3. Pharmacokinetics
`David W. A. Bourne
`
`4. Factors Influencing Drug Absorption and Drug Availability
`Betty-ann Hoener and Leslie Z. Benet
`
`,·
`
`5. The Effect of Route of Administration and Distribution on Drug Action
`Svein @ie and Leslie Z. Benet
`
`6. Chemical Kinetics and Drug Stability
`J. Keith Guillory and Rolland I. Foust
`
`7. Preformulation
`Jens T. Carst(?nsen
`
`8. Cutaneous and Transdermal Delivery-Processes and Systems of Delivery
`Gordon L. Flynn
`
`9. Disperse Systems
`Wandee Im-Emsap, Omlaksana Paeratakul, and Juergen Siepmann
`
`V
`
`iii
`ix
`
`23
`
`67
`
`93
`
`119
`
`139
`
`167
`
`187
`
`237
`
`
`
`vi
`
`10. Tablet Dosage Forms
`Mary J. Kottke and Edward M. Rudnic
`
`11. Hard and Soft Shell Capsules
`Larry L. Augsburger
`
`12. Parenteral Products
`James C. Boylan and Steven L. Nail
`
`13. Design and Evaluation of Ophthalmic Pharmaceutical Products
`John C. Lang, Robert E. Roehrs, Denise P. Rodeheaver, Paul J. Missel, Rajni Jani, and
`Masood A. Chowhan
`
`14. Delivery of Drugs by the Pulmonary Route
`Anthony J. Hickey
`
`15. Sustained- and Controlled-Release Drug Delivery Systems
`Gwen M. Jantzen and Joseph R. Robinson
`
`16. Target-Oriented Drug-Delivery Systems
`Vijay Kumar and Gilbert S. Banke1·
`
`17. Packaging of Pharmaceutical Dosage Forms
`Thomas J. Ambrosio
`
`18. Optimization Techniques in Pharmaceutical Formulation and Processing
`Joseph B. Schwartz, Robert E. O'Connor, and Roger L. Schnaare
`
`..)
`
`19. Food and Drug Laws that Affect Drug Product Design, Manufacture, and
`Distribution
`Garnet E. Peck and Roland Poust
`
`20. European Aspects of the Regulation of Drug Products with Particular Reference
`to Development Pharmaceutics
`Brian R. Matthews
`
`21. Pediatric and Geriatric Aspects of Pharmaceutics
`Michelle Danish and Mary Kathryn Kottke
`
`.
`22. Biotechnology-Based Pharmaceuticals
`Paul R. Dal Monte, S. Kathy Edmond Rouan, and Narendra B. Bam
`
`23. The Pharmacist and Veterinary Pharmaceutical Dosage Forms
`J. Patrick McDonnell and Lisa Blair Banker
`
`24. Dietary Supplements
`Teresa Bailey Klepser
`
`25. Bioequivalency
`Christopher T. Rhodes
`
`Contents
`
`287
`
`335
`
`381
`
`415
`
`479
`
`501
`
`529
`
`587
`
`607
`
`627
`
`645
`
`667
`
`695
`
`725
`
`735
`
`751
`
`
`
`Contents
`
`26. Drug Information
`Hazel H. Seaba
`
`27. Managed Care and Pharmacotherapy Management
`Julie M. Ganther and William R. Doucette
`
`28. A View to the Future
`Gilbert S. Banker and Christopher T. Rhodes
`
`Index
`
`vii
`
`767
`
`799
`
`813
`
`833
`
`
`
`Chapter 10
`
`Tab let Dosage Forms
`
`Mary Kathryn Kottke
`
`Cubist Plzarmaceuticals, I11c., Lexington, Massachusetts
`
`Edward M. Rudnic
`
`Advancis Pharmace11lical Corp., Gaithersburg, Maryland
`
`I. INTRODUCTION
`·,.
`During the past four decades, the pharmaceutical in(cid:173)
`dustry has· invested vast amounts of time and money in
`the study of tablet compaction. This expenditure is
`quite reasonable when one considers how valuable
`tablets, as a dosage form, are to the industry. Because
`oral dosage forms can be self-administered by the pa(cid:173)
`tient, they are obviously more profitable to manu(cid:173)
`facture than parenteral dosage forms that must be
`administered, in most cases, by trained personnel. This
`is reflected by the fact that well over 80% of the drugs
`in the United States that are formulated to produce
`systemic effects are marketed as oral dosage fonns.
`Compared to other oral dosage forms, tablets are the
`manufacturer's dosage form of choice because of their
`relatively low cost of manufacture, package, and
`shipment; increased stability and virtual tamper re(cid:173)
`sistance (most tampered-with tablets either become
`discolored or disintegrate).
`
`II. DESIGN AND FORMULATION
`OF COMPRESSED TABLETS
`A. General Considerations
`in con(cid:173)
`The most common solid dosage forms
`temporary use are tablets, which may be defined as
`
`unit forms of solid medicaments prepared by com(cid:173)
`paction. Most consist of a mixture of powders that are
`compacted in a die to produce a single rigid body. The
`most common types of tablets are those intended to be
`swallowed whole and then disintegrate and release
`their medicaments in the gastrointestinal tract (GIT).
`A less common type of tablet that is rapidly gaining
`popillarity in the United States is formulated to allow
`dissolution or dispersion in water prior to adminis(cid:173)
`tration. Ideally, for this type of tablet all ingredients
`should be soluble, but frequently a fine suspension bas
`to be accepted. Many tablets of this type are for(cid:173)
`mulated to be effervescent, and their main advantages
`include ~apid release of drug and minimization of
`gastric irritation.
`Some tablets are designed to be masticated (i.e.,
`chewed). This type of tablet is often used when ab(cid:173)
`sorption from the buccal cavity is desired or to en(cid:173)
`hance dispersion prior to swallowing. Alternatively, a
`tablet may be intended to dissolve slowly in the mouth
`(e.g., lozenges) so as to provide local activity of the
`drug. A few tablets are designed to be placed under the
`tongue (i.e., subliugual) or between the teeth and gum
`(i.e., buccal) and rapidly release drug into the blood(cid:173)
`stream. Buccal or sublingual absorption is often
`desirable for drugs liable to extensive hepatic meta(cid:173)
`bolism by the first-pass effect (e.g., nitroglycerin,
`
`287
`
`
`
`288
`
`testosterone). Recently, a lozenge on a stick, or "lol(cid:173)
`lipop," dosage form of fentanyl was developed for
`preoperative sedation in pediatric patients (Oralet®)
`and breakthrough cancer pain in adults (Actiq®).
`Active ingredient is released from the lozenge into the
`bloodstream from the oral mucosa.
`There are now many types of tablet formulations
`that provide for the release of drug to be delayed or
`control the rate of the drug's availability. Some of
`these preparations are highly sophisticated and are
`rightly referred to as complete "drug-delivecy sys(cid:173)
`tems." Since the concepts of controlled drug delivery
`are the subjects of Chapter 15, the strategies of these
`systems will not be discussed here. However, solid
`dosage formulators must be aware of the various op(cid:173)
`tions available to them.
`For example, when prolonged release of a water(cid:173)
`soluble drug is required, water-insoluble materials
`must be co-fonnulated with the drug. If the dos~ of the
`drug is high and it exhibits poor compactibility, purely
`hydrophobic agents, such as waxes, will exacerbate the
`inability of the material to form a compact. In such
`cases, formulators need to turn to other types of water(cid:173)
`insoluble materials, such as polymers, to achieve both
`drng release and tableting goals.
`Some tablets combine sustained-release and rapid
`disintegration characteristics. Products such as K(cid:173)
`Dur® (Key Pharmaceuticals) combine coated po(cid:173)
`tassium chloride crystals in a rapidly releasing tablet.
`In this particular instance, the crystals are coated with
`ethylcellulose, a water-insoluble polymer, and are then
`incorporated into a rapidly disintegrating micro(cid:173)
`crystalline cellulose (MCC) matrix. The purpose of this
`tablet is to minimize GI ulceration, commonly en(cid:173)
`countered by patients treated with potassium chloride.
`This simple but elegant formulation is an example of a
`solid dosage fo1m strategy used to achieve clinical
`goals.
`Thus, the single greatest challenge to t he tablet
`formulator is in the definition of the purpose of the
`formulation and the identification of suitable materials
`to meet development objectives. In order to do this
`properly, the formulator must know the properties of
`the drug, the materials to be co-formulated with the
`drug, and the important aspects of the granulation,
`tableting, and coating processes.
`Pharmaceutical compressed tablets are prepared by
`placing an appropriate powder mix, or granulation, in
`a metal die on a tablet press. At the base of the die is a
`lower punch, and above the die is an upper punch.
`When the upper punch is forced down on the powder
`mix (single station press) or when the upper and lower
`
`Kottke and Rudnic
`
`punches squeeze together (rotary or multiple station
`press), the powder is forced into a tablet. Despite the
`fact that powder compaction has been observed for
`hundreds of years, scientists still debate the exact me(cid:173)
`chanisms behind this phenomenon.
`Perhaps the most significant factor in the tableting
`of materials for use as drug products is the need to
`produce tablets of uniform weight. This is achieved by
`feeding constant volumes of homogeneous material to
`the dies. Such an approach is necessary because direct
`weighing at rates commensurate with modern tablet
`press operation is impossible. This requirement im(cid:173)
`mediately places demands on the physical character(cid:173)
`istics of the feed and on the design of the tablet press
`itself. In the case of the former, precompression
`treatment of the granulation is one of the most com(cid:173)
`mon ways of minimizing difficulties arising from this
`source.
`The great paradox in pharmaceutical tableting is the
`need to manufacture a compact of sufficient mechan(cid:173)
`ical strength to withstand the rigors of processing and
`packaging that is also capable of reproducibly releas(cid:173)
`ing the drug. In most cases, the release of the drug is
`produced by the penetration of aqueous fluids into the
`fine residual pore structure of the tablet and the con(cid:173)
`tact of these fluids with components that either swell or
`release gases.
`The selected precompression treatment, if any,
`markedly affects the manufacture of tablets. In parti(cid:173)
`cular, one must determine whether a mixture of pow(cid:173)
`dered ingredients is to be tableted directly or if an
`intervening wet granulation step is to be introduced.
`This decision is influenced by many factors, including
`the stability of the drug to heat and moisture; the fl.ow
`properties of the granulation; and the tendency of the
`granulation to segregate. At the present time there are
`also two conflicting considerations that tend to play a
`major role in this choice. These are the reluctance to
`change methods employed traditionally by the com(cid:173)
`pany versus the economic advantages of omitting
`complete stages in the production sequence.
`In wet granulation, the components of the for(cid:173)
`mulations are mixed with a granulating liquid, such as
`water or ethanol, to produce granules that will readily
`compress to give tablets. Wet granulation methods
`predominate in the manufacture of existing products,
`while the trend for new products is to use direct
`compression procedures. Although many steps are
`eliminated when using direct compression, some for(cid:173)
`mulat0rs have found that wet granulated products are
`more robust and able to accommodate variability in
`raw materials and tableting equipment. Thus, for some
`
`-
`
`
`
`Tablet Dosage Forms
`
`289
`
`companies, lhe trend is reverting to the formulation of ·
`tablets by wet granulation.
`
`B. Desirable Properties of Raw Materia"ls
`
`Most formulations are composed of one or more
`medicaments plus a variety of excipients. Irrespective
`of the type of tablet, general criteria for these raw
`materials are necessary. In order to produce accurate,
`reproducible dosage forms, it is essential that each
`component be uniformly dispersed within the mixture
`and that any tendency for component segregation be
`minimized. In addition, the processing operations de(cid:173)
`mand that the mixture be both free-flowing and co(cid:173)
`hesive when compressed.
`
`Particle Size
`
`In general, the tendencies for a powder mix to segre(cid:173)
`gate can be reduced by maintaining similar particle size
`distribution, shape, and, theoretically, density of all the
`ingredients. Flow properties are enhanced by using
`regular-shaped, smooth particles with a narrow size
`distribution together with an optimum proportion of
`":fi)les" (particles 50 µm) . If such conditions cannot be
`met, then some form of granulation should be
`considered.
`Particle size distribution, and hence surface area of
`the drug itself, is an important property that has re(cid:173)
`ceived considerable attention in the literature. For
`many drugs, particularly those whose absorption is
`limited by the rate of dissolution, attainment of ther(cid:173)
`apeutic levels may depend upon achi~ving a small
`particle size [1]. In fact, it has been suggested that for
`such drugs, standards for specific surface areas and the
`number of particles per unit weight should be devel(cid:173)
`oped. However, the difficulty in handling very fine
`powders, as well as the possibility of altering the ma(cid:173)
`terial in other ways, has shifted the emphasis towards
`producing an optimum, rather than a minimum, par(cid:173)
`ticle size. For instance, several researchers have found
`that decreasing particle size produces tablets of in(cid:173)
`creased strength that also have a reduced tendency for
`lamination [2- 5]. This is probably due to the mini(cid:173)
`mization of any adverse influences that a particular
`crystal structure may have on the bonding mechanism.
`On the other hand, samples of milled digoxin crystals
`prepared by a number of size-reduction techniques
`have been reported to elicit different equilibrium so(cid:173)
`lubilities [l]. This suggests that the method of grinding
`may well affect the dissolution behavior of certain
`drugs.
`
`The effect of particle size on the compaction char(cid:173)
`acteristics of two model sulfonamide drugs, one ex(cid:173)
`hibiting brittle fracture and the other being compressed
`chiefly by plastic deformation, has been reported [3]. In
`particular, it was shown that the tensile strength of
`tablets made from the brittle material were more sen(cid:173)
`sitive to the drug's particle size than that of tablets
`made from the plastically deforming material. In ad(cid:173)
`dition, larger granules possess better flow, while small
`aggregates deform during compaction (e.g., spray(cid:173)
`dried lactose) [6].
`An alternative approach aimed at reducing · the
`segregation tendencies of medicaments and excipients
`involves milling the former to a small particle size and
`then physically absorbing it ltniformly onto the surface
`of the larger particles of au excipient substrate. By
`these means "ordered," as opposed to "random,"
`mixing is realized and dissolution is enhanced as a
`result of the fine dispersion [7].
`
`Moisture Content
`
`One of the most significant parameters conh"ibuting to
`the behavior of many tablet formulations is the level of
`moisture present during manufacture as well as that
`residual in the product. In addition to its role as a
`granulation fluid and its potentially adverse effects on
`stability, water has some subtle effects that should not
`be overlooked. For example, there is increasing evi(cid:173)
`dence to suggest that moistme levels may be very cri(cid:173)
`tical in minimizing certain faults, such as lamination,
`that can occur during compression. Moisture levels can
`also affect the mechanical strength of tablets and may
`act as an internal lubricant. For example, Fig. 1 illus-
`
`300
`
`250
`
`5.13%
`
`3.53%
`1.93%
`
`200
`
`7
`a.
`£
`I! 150
`
`::, ! 100
`
`50
`
`0 -1--~-~~ -~~~ -~~ -~ - - ,
`s
`7
`3
`9
`11
`1
`Hardness (kg)
`
`Fig. 1 The effect of moisture content on the compactibility
`of anhydrous beta lactose tablets. (From Ref. 8.)
`
`
`
`290
`
`Kottke and Rudnic
`
`trates the effect of moisture content on the compact(cid:173)
`ibility of anhydrous lactose [8]. As the moisture con(cid:173)
`tent increases, it is adsorbed by the lactose, thereby
`converting it from the anhydrnus to the hydrous form.
`During this transformation, the ~-form of lactose most
`probably changes to the a.-form and thus produces
`changes in compactibility.
`Accelerated aging and crystal transformation rates
`have also been traced to high residual moisture con(cid:173)
`tent. Ando et al. studied the effect of moisture content
`on the crystallization of anhydrous theophylline in
`tablets [9]. Their results also indicate that anhydrous
`materials convert to hydrates at high levels of relative
`humidity. In addition, if hygroscopic materials (e.g.,
`polyethylene glycol 6000) are also contained in the
`formulation, needle-like crystals form at the tablet
`surf ace and significantly reduce the release rate of the
`theophylline.
`In many products it seems highly probable that
`there exists a narrow range of optimum moisture
`contents that should be maintained. More specifically,
`the effect of moisture on MCC-containing tablets has
`been the subject of an investigation that demonstrates
`the sensitivity of this important excipient to moisture
`content [10]. These researchers found that differences
`exist in both the cohesive nature and the moisture
`content to two commercial brands of MCC. A veTy
`useful report on the equilibrium moistw-e content of
`some 30 excipients has been compiled by a collabora(cid:173)
`tive group of workers from several pharmaceutical
`companies and appears in the Handbook of Pharma(cid:173)
`ceutical Excipients [11,12].
`
`Crystalline Form
`Selection of the most suitable chemical form of the
`active principle for a tablet, while not strictly within
`our terms of reference here, must be considered. For
`example, some chloramphenicol esters produce little
`clinical response [13]. There is also a significant dif(cid:173)
`ference in the bioavailability of anhydrous and hy(cid:173)
`<irated forms of ampicillin [14]. Furthermore, different
`polymorphic forms, and even crystal habits, may have
`a pronounced influence on the bioavailability of some
`drugs due to the different dissolution rates they exhibit.
`Such changes can also give rise to manufacturing
`problems. Polymorph.ism is, of course, not restricted to
`active ingredients, as shown, for example, in an eva(cid:173)
`luation of the tableting characteristics of five forms or
`sorbitol [15].
`Many drugs have definite and stable crystal habits.
`Morphological changes rarely occur in such drugs as
`
`Table 1 Some Drugs That Undergo Polymorphic Transi(cid:173)
`tion When Triturated
`
`Number of
`polymorpbs
`before tritura tion
`
`Number of
`polymorpbs
`after trituration
`
`2
`2
`'3
`2
`2
`3
`4
`4
`3
`2
`2
`
`l
`I
`2
`3
`1
`1
`5
`3
`2
`I
`1
`
`Drug
`
`Barbi tone
`Caffeine
`Chlorpropamide
`Clenbuterol HCI
`Dipyridamole
`Maprotiline HCI
`Mebendazole
`Nafoxidine HCI
`Pentobarbitone
`Phenobarbitone
`Sulfabeozamide
`
`Source: Ref. 16.
`
`the formulation process is scaled up. However, some
`drugs exhibit polymorphism or have different identifi(cid:173)
`able crystal habits. Chan and Doelker reviewed a
`number of drugs that undergo polymorphic transfor(cid:173)
`mation when triturated in a mortar and pestle [16].
`Some of their conclusions are listed in Table 1 and il(cid:173)
`lustrated in Fig. 2. In addition, a number of re(cid:173)
`searchers have concluded that both polymorph and
`crystal habit influence the compactibility and me(cid:173)
`chanical strength
`to
`tablets prepared from poly(cid:173)
`morphic materials
`[16-21]. York compared
`the
`compressibility of naproxen crystals that had been
`spherically agglomerated with different solvents and
`found that significant differences existed between the
`various types of agglomerates (see Fig. 3) [21]. Other
`investigators have found that, in some instances, there
`is a correlation between the rate of reversion to the
`metastable form during dissolution and the crystal
`growth rate of the stable form [22]. These polymorphic
`changes may have a profound effect on tablet perfor(cid:173)
`mance in terms of processing, in vitro dissolution and
`in vivo absorption. Thus, formulators of solid dosage
`forms must be aware of a subject compou nd's pro(cid:173)
`pensity for polymorphic transition so that a rational
`approach to formulation can be followed.
`
`Hiestand Tableting Indices
`
`Materials that do not compress well produce soft ta(cid:173)
`blets. In addition, brittle crystalline materials will yield
`brittle tablets. Hiestand was the first pharmaceutical
`scientist to quantify rationally the compaction prop(cid:173)
`erties of pharmaceutical powders [23- 28]. The results
`
`
`
`Tablet Dosage Forms
`
`\.
`
`291
`
`undergo plastic transformation to produce a suitable
`tablet. The third index, the brittle fracture index (BFI),
`is a measme of the brittleness of the material and its
`compact. Table 2 lists these indices for a number of
`drugs and excipients. For most materials, the strength
`of the tablet is a result of competing processes. For
`example, erythromycin is a material known for its
`tendency to cap and laminate when tableted. On the
`basis of its BI value, one might expect relatively good
`bonding. However, the very high strain index asso(cid:173)
`ciated with this drug appears to overcome its b onding
`abilities. MCC, on the other hand, has very high strain
`index, but its bonding index is exceptionally high and
`compensates for this effect.
`Other investigators have evaluated the potential for
`these indices. In their studies, Williams and McGinnity
`have concluded that evaluation of single-material sys(cid:173)
`tems should precede binary or tertiary powder systems
`[29]. A full discussion of compaction mechanisms is
`given later in this chapter.
`
`Variability
`The effect of raw material variability on tablet pro(cid:173)
`duction [2,30,3 1] and su ggestions for improving ta(cid:173)
`bleting quality of starting materials [21] has been the
`subject of several publications. Table 3, which lists the
`characteristics of different sources of magnesium
`stearate, clearly illustrates the variability of this ma(cid:173)
`terial [32]. Phadke and Eichorst have also confirmed
`that significant differences can exist between different
`sources, and even different lots, of magnesium stearate
`[33). Given the fact that the effectiveness of magnesium
`stearate is due, in large part, to its large surface area,
`these varfations should not be overlooked. In addition,
`studies assessing raw material variability emphasize the
`need for physical as well as chemical testing of raw
`materials to ensure uniformity of the final product.
`
`Purity
`Raw material purity, in general, must also be given
`careful attention. Apart from the obvious reasons for a
`high level of integrity, as recognized by the regulatory
`requirements, one should be aware of more subtle
`implications that are perhaps only just beginning to
`emerge. For instance, small proportions of the im(cid:173)
`purity acetylsalicylic anhydride have been shown to
`reduce the dissolution rate of asph-in itself (see Fig. 4)
`[34].
`Another area of interest is that of microbiological
`contamination of solid dosage fo rms, which is thought
`to arise chiefly from raw materials rather than the
`
`0
`50
`
`350
`
`250
`150
`Pressure (MPa)
`
`- Lower Surface
`- Upper Surface
`- Side
`
`---+- Middle Region
`
`Fig. 2 Percentage of caffeine "form A" transformed vs.
`applied pressure. (From Ref. 16.)
`
`of this work are three indices known as the Hiestand
`Tableting Indices. The strain index (SI) is a measure of
`the internal entropy, or strain, associated with a given
`material when compacted. The bonding index (Bl) is a
`measm e of the material's ability to form bonds and
`
`15
`
`10
`
`0 -I--.---.-..--~----.-....-~---.--..---,--.---,
`3000 3500
`2000
`1500
`2500
`500
`1000
`Pressure (lbs)
`
`- Control
`- Octanol
`
`~ Hexanol
`
`- - 0 - - Toluene
`
`Intrinsic compressibility of nonagglomerated na(cid:173)
`Fig. 3
`proxen (control) a nd of naproxen that has been spherically
`agglomerated with different solvents. (From Ref. 21.)
`
`
`
`292
`
`Kottke and Rudnic
`
`Table 2 Hiestand Compaclion Indices for Some Drugs and
`Excipients
`
`Table 3 Average Particle Data for Different Sources of
`Magnesium Stearate
`
`Bonding
`index
`
`Brittle
`Strain
`fracture index index
`
`Source
`
`Material
`
`Aspirin
`Caffeine
`Croscarmellose sodium NF
`Dicalcium phosphate
`Erytbromycin dihydrate
`Hydroxypropyl cellulose
`Ibuprofen
`A
`B
`C
`Lactose USP
`Anhydrous
`Hydrous Fast-Flo
`Hydrous bolted
`Hydrous spray process
`Spray-dried
`A
`B
`Mannitol
`A
`B
`Methenamine
`Methyl cellulose
`Microcrys talline
`cellulose NF
`Avicel PH 102 (coarse)
`Avicel PH 101 (fine)
`Povidone USP
`Sorbitol NF
`Starch NF
`Corn
`Pregelatinized
`Pregelatinized compressible
`Modified (starch 1500)
`Sucrose NF
`A
`B
`C
`
`Source: Refs. 23-28.
`
`1.5
`1.3
`2.7
`1.3
`l.9
`1.6
`
`1.9
`1.8
`2.7
`
`0.8
`0.4
`0.6
`0.6
`
`0.6
`0.5
`
`0.8
`0.5
`1.6
`4.5
`
`4.3
`3.3
`1.7
`0.9
`
`0.4
`J.8
`1.2
`1.5
`
`1.0
`0.8
`0.5
`
`0.16
`0.34
`0.02
`0.15
`0.98
`0.04
`
`0.05
`0.57
`0.45
`
`0.27
`0.19
`0.12
`0.45
`
`0. 18
`0.12
`
`0.19
`0.15
`0.98
`0.06
`
`0.04
`0.04
`0.42
`0.16
`
`0.26
`0.14
`0.02
`0.27
`
`0.35
`0.42
`0.53
`
`1.11
`2. 19
`3.79
`1.13
`2.13
`2.10
`
`0.98
`1.51
`1.21
`
`1.40
`1.70
`2.16
`2.12
`
`1.47
`1.81
`
`2. 18
`2.26
`0.84
`3.02
`
`2.20
`2.37
`3.70
`1.70
`
`2.48
`2.02
`2.08
`2.30
`
`1.45
`1.79
`1.55
`
`manufacturing process [35,36). Ibrahim and Olur(cid:173)
`inaola monitored the effects of production, environ(cid:173)
`ment and method of production, as well as microbial
`quality of starting materials, on the microbial load
`during various stages of tablet production [35). Al(cid:173)
`though high levels of contamination were present
`during the wet granulation process, these levels were
`significantly reduced during the drying process. The
`investigators a lso found that products derived from
`
`Size
`(µm)
`
`l.5- 3.2
`2.1- 5.2
`4.1-6.9
`5.5-9.1
`
`Surface
`area (m2/g)
`
`Pore radius
`cA)
`
`13.4
`12.2
`7.4
`4.6
`
`50
`68
`61
`36
`
`United States
`Great Britain
`Germany
`Italy
`
`Source: Ref. 32.
`
`natural ongms, such as gelatins and starch, can be
`contaminated heavily.
`
`Compatibility
`
`One final area that should be considered when choos(cid:173)
`ing the excipients to be used in the tablet formulation is
`that of drug-excipient interactions. There is still much
`debate as to whether excipient compatibility testing
`should be conducted prior to formulation (37- 39).
`These tests most often involve the trHuration of small
`amounts of the active ingredient with a variety of ex(cid:173)
`cipients. Critics of these small-scale studies argue that
`their predictive value has yet to be established and
`indeed do not reflect actual processing conditions [37).
`Instead, they suggest a sound knowledge of the
`chemistry of the materials used in conjuncture with
`"mini-formulation" studies as a preferable method for
`investigation of drug-excipient interactions.
`
`1.4
`
`1.2
`
`y = 1.3094 - 0.30351 x RA2 = 0.978
`
`.. ~
`
`a: 1.0
`C
`0 :.::: :,
`.,
`0 0.8
`.!'.!
`0
`
`0.6
`
`0.4
`0
`
`2
`% Acetylsallcyllc Anhydride
`
`3
`
`Fig. 4 Effecl of acetylsalicylic anhydride impurity on the
`dissolution rate of aspirin tablets. (From Ref. 34.)
`
`
`
`Tablet Dosage Forms
`
`293
`
`C. Tablet Components
`Conventional solid dosage forms can be divided into
`two classes: those that disintegrate and those that do
`not. Disintegrating dosage forms release drug by
`breaking down the physical integrity of the dosage
`from, usually with the aid of solid disintegrating agents
`or gas-releasing effervescent agents. Nondisintegrating
`tablets are usually made of soluble drugs and ex(cid:173)
`cipients that will rapidly dissolve in the mouth or GIT
`upon ingestion.
`With the advent of prolonged-release dosage forms,
`some pharmaceutical scientists have begun to regard
`conventional disintegrating dosage forms as "non(cid:173)
`controlled-release." This term is a misnomer since,
`with the aid of "super-disintegrants" and other ex(cid:173)
`cipients, the disintegration of these dosage forms can
`be controlled, both quantitatively and qualitatively.
`Moreover, there are still many drugs in which rapid
`attainment of therapeutic levels, rather than controlled
`release, is required. Analgesics, antibiotics, and drugs
`for the acl.}te treatment of angina pectoris are prime
`examples. These tablets need to be designed so that the
`drug is liberated from the dosage form in such a
`manner that dissolution of the drug is maximized. Very
`often, this means that disintegration of the tablet must
`be followed by granular disintegration (see Fig. 5) to
`promote rapid dissolution and, hence, absorption.
`The ingredients, or excipients, used to make com(cid:173)
`pressed tablets are numerous. They can be classified by
`their use, or function, as in Table 4. Keep in mind,
`however, that formulations need not contain all the
`types of ingredients listed in this table. Certain ex(cid:173)
`cipients, such as antioxidants and wetting agents, are
`used only in situations where they are expressly needed
`. to assure the stability and solubility of the active in(cid:173)
`gredients. Other excipients, such as dissolution modi(cid:173)
`in controlled-release
`fiers,
`are used primarily
`formulations. In fact, by reducing the number of in(cid:173)
`gredients in a formulation, one will generally be re(cid:173)
`ducing the number of problems that can arise in the
`manufacturing process. Hence, many formulators ad(cid:173)
`here to the motto "Keep it simple."
`Because of the nature of modern pharmaceutical
`systems, formulators have made more complete in(cid:173)
`vestigations of the materials they use. This interest has
`identified several materials that may have more than one
`use in tableted systems. The type of effect that an ex(cid:173)
`cipient will produce is often dependent upon the con(cid:173)
`centration in which it is used. For example, Table 5 lists
`some "multiuse" excipients and the corresponding con(cid:173)
`centration ranges required for their various applications.
`
`,).
`
`lntect Tablet
`
`DRUG IN
`BLOODSTREAM
`
`l
`zz Biological
`
`Membrane
`
`DRUG IN
`SOLUTION
`
`Fig. 5 Absorption of a drug from an intact tablet.
`
`A relatively new class of "co-processed" excipients
`now exists. These excipients are essentially a "pre(cid:173)
`blend" of two or more excipients that are commonly
`used in conjunction with each other.
`
`Active Ingredients
`The dose of the drug to be administered has a pro(cid:173)
`found effect on the design and formulation of a dosage
`form. Content uniformity and drug stability become
`very important issues when dealing with highly potent
`compounds that are delivered in very small doses (e.g.,
`oral contraceptives). However, the effect of the drug's
`properties on the tablet, in this case, is minimal. In
`general, as the dosage increases, so does the effect of
`the drug's attributes on the tablet.
`
`Table 4 Ingredients Used in Tablet Formulation
`
`Active ingrerueut .(drug)
`Fillers
`Binders (dry and wet)
`Disintegrants
`Antifrictional agents
`Lubricants
`Glidants
`Antiadherants
`
`Dissolution modifiers
`Absorbents
`Flavoring agents
`Coloring agents
`Wetting agents
`Antioxidants
`Preservatives
`
`
`
`294
`
`Kottke and Rudnic
`
`Table 5 Some Multiple-Use Excipients for Tablet Formulation
`
`Excipient/concentration in formula
`
`Ethylcellulose
`1- 3%
`1- 3%
`Glyceryl palmitostearate
`0- 5%
`10- 50%
`Hydroxypropylmethyl cellulose (HPMC), low
`viscosity
`2- 5%
`2