The Theory
`and Practice of Industrial
`Pharmacy
`
`LEON LACHMAN, Ph.D.
`Lachman Consultant Services, Inc.
`Garden City, New York
`HERBERT A. LIEBERMAN, Ph.D.
`H. H. Lieberman Associates, Inc.
`Consultant Services
`Livingston, New Jersey
`JOSEPH L. KANIG, Ph.D.
`Kanig Consulting and Research Associates, Inc.
`Ridgefield, Connecticut
`
`THIRD EDITION
`
`LEA & FEBIGER• 1986 • PHILADELPHIA
`
`Novartis Exhibit 2186.001
`Regeneron v. Novartis, IPR2021-00816
`
`

`

`I
`
`Lea & Febiger
`600 Washington Square
`Philadeiphia, PA 19106-4198
`U.S.A.
`(215) 922-1330
`
`'- 1 a8AR"'
`
`Library of Congress Cataloging in Publication Data
`Main entry under title:
`
`The Theory and practice of industrial phannacy.
`
`Includes bibliographies and iridex.
`I. Lachman, Leon,
`1. Phannacy.
`2. Drug trade.
`1929-
`IL Lieberman, Herbert A., 1920-
`Ill. Kanig, Joseph L., 1921-
`[DNLM: 1. Drug
`Industry.
`QV 704 T396]
`615' .19
`RS192.L33 1985
`ISBN 0-8121-0977-5
`
`84-27806
`
`First Edition, 1970
`Second Edition, 1976
`
`Copyright © 1986 by Lea & Febiger. Copyright under the
`International Copyright Union. All Rights Reserved. This
`book is protected by copyright. No part of it may be repro(cid:173)
`duced iri any manner or by any means without written per(cid:173)
`mission from the publisher.
`
`PRINTED IN THE UNITED STATES OF AMEJ-UCA
`
`Print No. 4 3 2 1
`
`Novartis Exhibit 2186.002
`Regeneron v. Novartis, IPR2021-00816
`
`

`

`Dry Heat. Substances that resist degradation
`at temperatures_ above approximately 140°C
`(284 °F) may be rendered sterile by means of dry
`heat. Two hours exposure to a temperature of
`180°C (356°F) or 45 min at 260°C (500°F) nor(cid:173)
`mally can be expected to kill spores as well as
`vegetative forms of all microorganisms. This
`total sterilizing cycle time normally includes a
`reasonable lag time for the substance to reach
`the sterilizing temperature of the oven chamber,
`an appropriate hold period to achieve steriliza(cid:173)
`tion, and a cooling period for the material to re(cid:173)
`turn to room temperature:
`Factors in Determining Cycle Time. The
`cycle time is composed of three parts: (1) the
`thermal increment time of both the chamber
`and the load of material to be sterilized, assum(cid:173)
`ing both start at room temperature, (2) the hold
`period at the maximum temperature, and (3) the
`cooling time. The material lags behind the in(cid:173)
`creasing temperature of the chamber. The time
`required for all of the material to "catch up" with
`the temperature of the chamber is longer with
`larger quantites of material, poorer thermal con(cid:173)
`ductance properties of the material; and lower
`heat capacity. The relationship of these factors
`must be carefully determined during validation
`studies so that effective cycle times can be
`planned.
`The cycle time is most commonly prescribed
`in terms of the hold time, for example, 2 hours at
`l 80°C dry heat. The hold time may be shown by
`sensors detecting_the temperature of the cham(cid:173)
`ber at its coolest spot; however, a better indica(cid:173)
`tion of the actual thermal condition is obtained
`by sensing, usually with a thermocouple, the
`coolest spot in the load of the material to be steri(cid:173)
`lized. When such a location is used, and when
`this coolest spot is lmown from previous valida(cid:173)
`tion studies, the timing required for sterilization
`is correctly programmable. It should be remem- -
`bered that other parts of the load of material may
`be heated for a longer period, and if it is ther(cid:173)
`mally unstable, degradation could occur. There(cid:173)
`fore, the thermal stability of the material io be
`sterilized must be lmown and the optimum
`method of sterilization selected to achieve eff ec(cid:173)
`tive sterilization throughout the entire mass of
`material while maintaining its stability and in(cid:173)
`tegrity.
`Sterilizer Types. The ovens used to achieve
`hot air sterilization are of two types, natural con(cid:173)
`vection and forced convection. Circulation
`within natural convection ovens depends upon
`the currents produced by the rise of hot air and
`fall of cool air. This circulation can be. easily
`blocked with containers, resulting in poor heat
`distribution efficiency. Differences in tempera-
`
`624 • The Theory and Practice of Industrial Pharmacy
`
`ture of :tb°C or more may be found in different
`shelf areas of even small laboratory ovens of the
`natural convection type. 14
`Forced convection ovens provide a blower to
`circulate the heated air around the objects in the
`chamber. Efficiency is greatly improved over
`natural convection. Temperature differences at
`various locations on the shelves may be reduced
`to as low as ± 1 °C. The lag times of the load ma(cid:173)
`terial therein also are greatly reduced because
`fresh hot air is circulated rapidly around the ob(cid:173)
`jects. The curves shown in Figure 21-3 illustrate
`the difference in lag time for some of the same
`containers-of com.oil when heated in a natural
`convection oven as compared with the same
`oven equipped for forced circulation. 14
`Another type of sterilizer is the tunnel unit
`with a moving belt, designed to thermally steril(cid:173)
`ize glass bottles and similar items as they move
`through the tunnel. The items are cooled with
`clean. air before they exit the tunnel, usually di(cid:173)
`rectly into an aseptic room and linked in a con(cid:173)
`tinuous line with a filling machine. Such units
`require careful validation. 15
`/
`Effect on Materials. The elevated tempera(cid:173)
`tures required for effective hot air sterilization in
`a reasonable length of time have an adverse ef(cid:173)
`fect on many substances. Cellulose materials,
`such as paper and cloth, begin to char at a tern"
`perature of about 160°C (320°F). At these tem(cid:173)
`peratures, many chemicals are decompose'd,
`rubber is rapidly oxidized, and thermoplastic
`materials melt. Therefore, this method of sterili(cid:173)
`zation is reserved largely for, glassware, metal(cid:173)
`ware, and anhydrous oils and chemicals that can
`
`(
`!DfE
`: :
`/
`! !
`'' I: /
`
`,i
`
`A-Oven
`B-600ml.
`C-IOOOml.
`D·-·Oven
`E--· 600 ml. bottle
`F--1000 ml. bottle
`
`0o 15 30 45 60 75 90
`120
`Time ( Minutes)
`FIG. 21-3. Rate of heating com oil in Pyrex liter bot(cid:173)
`tles in the same hot air aven with natural convection
`(-.-•--) and forced circulation (--•--) . .
`
`150
`
`180
`
`210
`
`139
`
`.A
`
`135
`
`/!? 130
`
`:;! e Q)
`
`~ 120
`~
`
`JOO
`
`I ' '
`' I '
`: I
`:
`l I
`/
`! ! !
`f I·:
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`' ' '
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`'
`l
`l
`l
`I
`,
`I
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`' : /
`'
`i
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`'
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`I
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`
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`
`I
`
`Novartis Exhibit 2186.003
`Regeneron v. Novartis, IPR2021-00816
`
`

`

`withstand the elevated temperature ranges
`without degradation. Expansion of materials is
`also appreciable, as they are heated from room to
`sterilizing temperatures. Therefore, glassware
`must not be wedged tightly in the oven cham(cid:173)
`ber, containers for oils must be large enough to
`permit expansion of the oil, and provision must
`be made for the expansion of other substances.
`Advantage may be taken of the anhydrous
`state achieved with this method of sterilization
`to provide dry glassware and metalware at the
`end of an adequate heating cycle. Dry equip(cid:173)
`ment and containers are essential in the manu(cid:173)
`facture of an anhydrous product, but they are
`also desirable to prevent dilution of an aqueous
`product. Also, dry equipment can be kept sterile
`during storage more easily than wet equipment.
`Further, dry heat effectively destroys pyrogens,
`usually requiring about twice the hold time for
`sterilization.
`To maintain a .sterile condition after steriliza(cid:173)
`tion, environmental contamination must be ex(cid:173)
`cluded. The openings of equipment must. be
`covered with a hairier material such as alumi(cid:173)
`num foil. As an alternative, items to be sterilized
`may be placed in a covered stainless steel box or
`similar protective container.
`Moist Heat. Moist heat is more effective
`than dry heat for thermal sterilization. It should
`be remembered, however, that normal moist
`heat cycles do not destroy pyrogens .
`.Ai,s previously noted, moist heat causes the
`coagulation of cell protein at a much lower tem(cid:173)
`perature than dry heat. In addition, the thermal
`capacity of steam is much greater than that of
`hot air. At the point of condensation (dew point),
`steam liberates thermal energy equal to its heat
`of vaporization. This amounts. to approximately
`540 calories per gram at 100°C (212°F) and 524
`calories per gram at 121 °C (250°F). In contrast,
`the heat energy liberated by hot dry air is equiv(cid:173)
`alent to approximately only 1 calorie per gram of
`air for each degree centrigrade of cooling. There(cid:173)
`fore, when saturated steam~trikes a cool object
`and is condensed, it liberates approximately 500
`times the amount of heat energy liberated by an
`equal weight of hot air. Consequently, the object
`is heated much more rapidly py steam. In addi(cid:173)
`tion, when steam under pressure is employed, a
`rapidly chang:i.Iig fresh supply of heat-laden
`vapor is applied to the object being heated. This
`is due both to the pressure under which steam is
`applied and to the partial vacuum produced at
`the site where steam is condensed, for it shrinks
`in volume by about 99% as it condenses.
`Air Displacement. The density of steam is
`lower than that of air. Therefore, steam enters
`an autoclave chamber a.pd rises to the top, dis-
`
`placing air downward, as illustrated by the grav(cid:173)
`ity displacement autoclave shown in Figure
`21-4. Objects must be placed in the chamber
`with adequate circulation space around each
`object, and so arranged that air can be displaced
`downward and out of the exhaust line from the
`chamber. Any trapped air, e.g., air in containers
`with continuous sides and bottoms or in tightly
`wrapped packs, prevents penetration of the
`steam to these areas and thus prevents steriliza(cid:173)
`tion. The air trapped in this manner is heated to
`the temperature of the steam, but hot air at a
`temperature of 120°C (248°F) requires a cycle
`time of 60 hours to ensure a lethal effect on
`spores. 16 A 20-min exposure at this temperature
`with hot dry air, therefore, would be entirely in(cid:173)
`adequate.
`Factors Determining Cycle Time. Spores
`and vegetative forms of bacteria may be effec(cid:173)
`tively destroyed in an autoclave employing
`steam under pressure during an exposure time
`of20 min at 15 pounds pressure (121 °C [250°F])
`or as little as 3 min at 27 pounds pressure
`(132°C [270°F]). These time intervals are based
`on the assumption that the steam has reached
`the innermost recess of the_material to be steri-
`
`FIG. 21-4. Cross-sectional diagram of the functional
`parts of an autoclave. (Courtesy of.American Sterilizer
`.
`Co.)
`
`STERILIZATION • 625
`
`Novartis Exhibit 2186.004
`Regeneron v. Novartis, IPR2021-00816
`
`

`

`lized, and that the temperature of the material is
`held for at least one half of that time interval. In
`the case of bottles of solution, the heat must be
`conducted through the wall of the container,
`raise the temperature of the solution to that of its
`environment, and generate steam within the
`container from the water therein. Therefore, a
`significant lag time is involved before the solu(cid:173)
`tion reaches the sterilizing temperature.
`The determination of lag time and its inclu(cid:173)
`sion in the planned total cycle time is no less
`important for moist heat sterilization than for
`hot air sterilization, discussed previously. By
`way of illustration, it has been found that 1200
`ampuls, each containing 5 ml of a solution, can
`be effectively sterilized in an autoclave at 121 °C
`(250°F) during an exposure time of 20 min.
`A single bottle containing the same total volume
`of solution (6 L) required an exposure of 60 min
`at 121°C (250°F)_11
`Air-Steam Mixtures. While air-steam mix(cid:173)
`tures have a lower temperature and lower ther(cid:173)
`mal capacity than pure steam, the presence of
`air may be utilized to control the pressure in the
`chamber when flexible-walled containers of
`products are being sterilized. For example, plas(cid:173)
`tic bags of large-volume parenterals (LVPs) or
`collapsible tubes of aqueous jellies would swell
`and burst in an autoclave utilizing steam only,
`particularly during the cooling phase. When air
`is mixed with the steam and the air pressure is
`independently controlled, the pressure applied
`to the outside of the containers can be adjusted
`to equal the internal pressure so that the con(cid:173)
`tainers do not burst. Because of the tendency of
`steam and air to stratify, the mixture must be
`mixed continuously; this is usually accom(cid:173)
`plished by means of a blower.
`Approaches to Reduction of Cycle Time.
`Prolonged heating of most objects is detrimental.
`to the material. For example, fabrics and rubber
`parts deteriorate with loss of tensile strength,
`solutions may . undergo adverse chemical
`changes, and metal objects may become pitted.
`Therefore, the total cycle time should be con(cid:173)
`trolled so that the heating period is not unneces(cid:173)
`sarily prolonged. Usually, this is best accom(cid:173)
`plished by shortening the cooling period. For
`nonsealed items of equipment or containers that
`do not contain solutions, the steam may be ex(cid:173)
`hausted to the outside rapidly at the end of the
`sterilizing cycle. Objects are thereby cooled rap(cid:173)
`idly, particularly if removed from the autoclave
`chamber. Such a procedure cannot be employed
`for solutions, whether sealed or unsealed in con(cid:173)
`tainers, because the rapid release of chamber
`pressure would cause violent ebullition of the
`hot solution, with spattering of the contents of
`
`unsealed c::ontainers and explosion of sealed con(cid:173)
`tainers.
`One method for rapid extraction of heat from
`sealed containers of solutions is to spray the con(cid:173)
`tainers with gradually cooling water while the
`pressure in the chamber is concurrently re(cid:173)
`duced. Another accelerated cooling method
`employs short pulses of high pressure steam in(cid:173)
`troduced into the loaded chamber. As the steam
`expands in the chamber it extracts heat from the
`containers of solution. The steam is exhausted
`from the chamber at a rate that provides for a
`gradual reduction of the pressure concurrent
`with the temperature reduction. By these meth(cid:173)
`ods, it is sometimes necessary to introduce
`pulses of air into the chamber to replace all or
`part of the steam so that the pressure around the
`containers is not reduced too rapidly. By the
`spray cooling method, it has been reported that
`the cooling time for a load of200 one-liter bottles
`of solution may be reduced from about 20 hours
`to about 20 min. 18
`·
`A relatively new approach to a reduction in
`the total heating cycle .time has been the intro(cid:173)
`duction of a precycle vacuum. In a specially de(cid:173)
`signed autoclave, a precycle vacuum of at.least
`20 mm Hg is drawn. More recent studies·have
`shown that a double vacuum drawn in sequence
`prior to th.e heating cycle removes air more ef(cid:173)
`fectively from porous materials.19 The subse(cid:173)
`quent introduction of steam permits rapid pene(cid:173)
`tration and
`load heating with complete
`elimination of air pockets. Since the total heat(cid:173)
`ing period is markedly reduced owing to the re(cid:173)
`duction in the temperature increment time, a
`higher temperature (usually 135°C [275°F]) may
`be employed with less deleterious effects on
`materials. This method is,particularly suited to
`operating room packs in hospitals, where the
`total cycle time for large packs has been reduced
`from about 78 min by the conventional method
`to about 14 min. Such a method cannot be used
`for solutions or other objects that cannot with(cid:173)
`stand the high vacuum employed.
`Lower Temperature Sterilization. Moist
`heat also is used fot lower temperature steriliza(cid:173)
`tion procedures. Temperatures of 100°C (212°F)
`· or lower are used for these so-called marginal, or
`fractional, methods. The term marginal origi(cid:173)
`nates from the questionable reliability of the
`processes. The term fractional is derived from
`the fact that these processes are normally per(cid:173)
`formed by two or three exposures to moist heat,
`alternated with intervals during which the mate(cid:173)
`rial is held at room or incubator temperatures.
`Fractional methods of sterilization such as
`tyndallization, employing a
`temperature of
`100°C (212°F), and inspissation, employing
`
`626 • The Theory and Practice of Industrial Pharmacy
`
`Novartis Exhibit 2186.005
`Regeneron v. Novartis, IPR2021-00816
`
`

`

`temperatures as low as 60°C (140°F), are rela(cid:173)
`tively effective in reducing the number of vege(cid:173)
`tative forms of microorganisms, but are umelia(cid:173)
`ble against spores. For certain preparations, the
`effectiveness of these processes niay be im(cid:173)
`proved by the inclusion of a bacteriostatic agent.
`These marginal methods of sterilization should
`be reserved for substances that must be proc(cid:173)
`essed by a thermal method but that cannot with(cid:173)
`stand higher temperatures without degradation.
`The assurance of sterility is comparatively low,
`however.
`Wrapping Ma£erials. Wrappings for equip(cid:173)
`ment and supplies subjected to moist heat steri(cid:173)
`lization must permit easy penetration of steam
`and escape of air. They must also possess suffi(cid:173)
`cient wet strength so that they will. not tear or
`burst during the process. After sterilization, the
`wrapping must provide an efficient bacterial
`barrier so that equipment remains sterile for a
`reasonable time until used. In addition, mainte(cid:173)
`nance of sterility depends upon complete cover(cid:173)
`age of the contents of the pack, drying of the
`wrapping after the process, and a static air state
`within. Acceptable disposable process wrapping
`materials include 20-lb weight Kraft paper, spe(cid:173)
`cial parchment paper, and Tyvek. Reusable
`types include close-weave nylon and Dacron.
`Except for Kraft paper, all are low-lint materials.
`Indicators for Evaluating the Steriliza(cid:173)
`tion Process. The duplication of proven ther(cid:173)
`mal ;methods of sterilization cannot be taken for
`granted. Mechanical equipment as well as per(cid:173)
`sonnel are subject to failure. Therefore, indica(cid:173)
`tors should be used as a check on the duplication
`of.the conditions of a proven (validated) process,
`locating the indicator where there is the greatest
`impediment to the penetration. of the heat.
`Among the indicators available, the most
`widely used is the thermocouple. These indica(cid:173)
`tors are often connected to recorders so that a
`continuous record of the actual temperature at
`the location of the thermocouple can be ob(cid:173)
`tained.
`For autoclave ,sterilization, a variety of other
`indicators also are used. These include wax or
`chemical pellets that melt at 121 °C and paper
`strips that are impregnated with chemicals that
`change color under the influence of moisture
`and heat. All of these have limited reliability for
`indicating the length of time that a temperature
`of 121 °C has been maintained.
`Resistant bacterial spores in sealed ampuls or
`impregnated in dry paper strips are used.as bio(cid:173)
`logic indicators. Their destruction is evidence of
`the .. intended effect of a sterilization process.
`Their use 'to prove the effectiveness of new ster(cid:173)
`ilizing equipment or processes is widely ac-
`
`cepted, 12 but their use as indicators for routine
`process control is questioned by some. Among
`the concerns are (l)lot to lot variability of the
`resistance of the spores, (2) lot to lot variability
`in the number of viable spores, (3) difficulty in
`obtaining pure cultures, and ( 4) the inherent
`danger of placing viable spores in a sterilizer
`load of materials for human use.
`Application of Thermal Methods of
`Sterilization. It is generally accepted that the
`most reliable thermal method of sterilization is
`the use of moist heat under pressure. Therefore,
`this method of sterilization should be employed
`whenever possible. Aqueous pharmaceutical
`preparations in hermetically sealed containers
`that can withstand the temperature of autoclav(cid:173)
`ing can be rendered sterile and remain so indefi(cid:173)
`nitely unless tampering with the seal occurs.
`Nonaqueous preparations in sealed containers
`cannot be sterilized in this manner during a nor(cid:173)
`mal cycle because no water is present within the
`container to generate steam and thereby effect
`sterilization.
`Moist heat sterilization is also applicable to
`equipment and supplies such as rubber clo(cid:173)
`sures, glassware, and other equipment'with rub(cid:173)
`ber attachments; filters of various types; and
`uniforms. To be effective, however, air pockets
`must be eliminated. This normally requires that
`the items be wet when placed in the autoclave.
`They also will be wet at the end of the sterilizing
`cycle. When moisture can escape without
`damage to the package, part of the moisture can
`be removed by employing an evacuation step at
`the end of the cycle. Even this process does not
`usually completely dry the equipment. There~
`fore, when such equipment is used in process(cid:173)
`ing, allowance must be made for the diluting ef(cid:173)
`fect of this water, or preferably, a small portion
`of the product may be used to rinse or flush the
`water out of the equipment. In some instances,
`when dry equipment is required and it must be
`sterilized by autoclaving, the equipment may be
`dried in a vacuum oven before use.
`Dry heat sterilization is used for containers
`and equipment whenever possible because an
`adequate cycle results in sterile and dry equip(cid:173)
`ment. High-speed processing lines recently de(cid:173)
`veloped have included a hot-air tunnel for the
`continuous sterilization of glass containers,
`which are heated by infrared lamps or by electri(cid:173)
`cally heated, filtered, circulating air. Glass and
`metal equipment usually withstand dry heat
`sterilization without difficulty, although uneven
`thermal expansion may cause breakage or dis(cid:173)
`tortion. Rubber and cellulosic materials undergo
`degradation, however. Certain ingredients, such
`as chemicals and oleaginous vehicles, to be used
`
`STERILIZATION• 627
`
`Novartis Exhibit 2186.006
`Regeneron v. Novartis, IPR2021-00816
`
`

`

`in sterile pharmaceutical preparations are some(cid:173)
`times sterilized with dry heat at lower (usually
`140°C or less) temperatures. In such cases, it
`must be established that the heating cycle has
`no deleterious effects on the ingredients and
`that the cycle time is adequate to achieve sterili(cid:173)
`zation. They also must be carefully protected
`after sterilization until incorporated aseptically
`in the product to prevent contamination from
`the environment.
`
`Nonthermal Methods
`Ultraviolet Light. Ultraviolet light is com(cid:173)
`monly employed to aid in the reduction of con(cid:173)
`tamination in the air and on surfaces within the
`processing environment. The germicidal light
`produced by mercury vapor lamps is emitted
`almost exclusively at a wave length of 2537 Ang(cid:173)
`strom units (253.7 millimicrons). It is subject to
`the laws for visible light, i.e., it travels in a
`straight line, its intensity is reduced in propor(cid:173)
`tion to the square of the relative distance it trav(cid:173)
`els, and it penetrates materials poorly or selec(cid:173)
`tively. Ultraviolet light penetrates clean air and
`pure water well, but an increase in the salt con(cid:173)
`tent and/or the suspended matter in water or air
`c:,i.uses a rapid decrease in the degree of penetra(cid:173)
`tion. For most other applications, penetration is
`negligible, and any germicidal action is confined
`to the exposed surface.
`·
`Lethal Action: When ultraviolet light passes
`through matter, energy is liberated to the orbital
`electrons within constituent atoms. This ab(cid:173)
`sorbed energy causes a highly energized state of
`the atoms and alters their reactivity. When such
`excitation and alteration of activity of essential
`atoms occurs within the molecules of microorga(cid:173)
`nisms or of their essential metabolites, the or~
`ganism dies or is unable to reproduce. The prin(cid:173)
`cipal effect may be on cellular nucleic acids,
`which have been shown to exhibit strong ab(cid:173)
`sorption bands within the ultraviolet wavelength
`range;
`The lethality of ultraviolet radiations has been
`well established; however, it also has been
`shown that organisms exposed to ultraviolet ra(cid:173)
`diations can sometimes recover, a fact not sur(cid:173)
`prising if the previously described theroy of le(cid:173)
`thality is correct. Recovery has been increased
`by the addition of certain essential metabolites
`to the culture, adjustment of the pH of the me(cid:173)
`dium, or exposure to visible light shortly after
`exposure to the ultraviolet radiations. Therefore,
`adequate exposure to the radiations must occur
`before reliance can be placed upon obtaining a
`sterilizing effect.
`
`628 • The Theory and Practice of Industrial Pharmacy
`
`The germicidal effectiveness of ultraviolet
`light is a function of the intensity of radiation
`and time of exposure. It also varies with the sus(cid:173)
`ceptibility of the organism. The data in Table
`21-4 show some of this range of susceptibility. 20
`From these data, it can be seen that if the inten(cid:173)
`sity of radia'tion on a surface was 20 microwatts
`per cm2
`, the minimum intensity usually recom(cid:173)
`mended, it would require approximately 1100
`seconds exposure to kill B. subtilis spores, but
`only approximately 275
`seconds
`to kill
`S. hemolyticus. The intensity of ultraviolet radi(cid:173)
`ation can be measured by means of a special
`light '[!,].eter having a phototube sensitive to the
`2537 A wavelength.
`Maintenance and Use. To maintain maxi(cid:173)
`mum effectiveness, ultraviolet lamps must be
`kept free from dust, grease, and scratches be(cid:173)
`cause of the large reduction in emission inten(cid:173)
`sity that will occur. Also, they must be replaced
`when emission levels decrease substantially
`(about 30 to 50%) owing to energy-induced
`changes in the glass,that inhibits the emission.
`Personnet present in areas where ultraviolet
`lights are on should be protected from the cli:rect
`and reflected rays. These rays cause reddening
`of the skin and intensely painful irritation of the
`eyes. The American Medical Association has
`recommended that the maximum safe human
`exposure for 1 hour be limited to 2.4 mw/cm.2
`Ultraviolet lamps are used primarily for their
`germicidal effect on surfaces or for their pene(cid:173)
`trating effect through clean air and water.
`Therefore,
`they are frequently installed in
`rooms, air ducts, and large equipment in which
`the radiation can pass through and irradiate the
`air, and' also reach exposed surfaces. Water sup-
`
`TABLE 21-4. Intensity of Radiation at 2537 A
`Necessary to Completely Destroy Certain Micro(cid:173)
`organisms
`
`Organism
`
`Bacillus subtilis
`B. subtilis spores
`Eberthella typhosa
`Escherichia coli
`Pseudomonas aeruginosa
`Sarcina hi.tea
`Staphylococcus aureus
`Streptococcus hemolyticus
`Saccharomyces cerevisiae
`Penicillium roqueforti
`Aspergillus niger
`Rhizopus nigricans
`
`Energy
`(mw.-sec./cm. 2
`
`)
`
`11,000
`22,000
`4,100
`6,600
`10,500
`26,400
`6,600
`5,500
`13,200
`26,400
`330,000
`220,000
`
`Novartis Exhibit 2186.007
`Regeneron v. Novartis, IPR2021-00816
`
`

`

`plies also have been sterilized when the limit of
`penetration has been carefully determined and
`controlled so that adequate irradiation through(cid:173)
`out has been achieved, ·
`Ionizing· Radiations.
`Ionizing radiations
`are high-energy radiations emitted from radioac(cid:173)
`tive isotopes su,ch as cobi1lt-60 (gamma rays) or
`produced by mechanical acceleration of elec(cid:173)
`trons to very high velocities and energies ( cath(cid:173)
`ode rays, beta rays). Gamma rays have the ad(cid:173)
`vantage of being absolutely reliable, for there
`can be no mechanical breakdown; however, they
`have the disadvantages that their source (radio(cid:173)
`active material) is relatively expensive and the
`emission cannot be shut off as it can from the
`mechanical source of accelerated electrons. Ac(cid:173)
`celerated electrons also have the advantage of
`providing a higher and more uniform dose rate
`output.
`Electron Accelerators. Electron accelera(cid:173)
`tors are of two general types, the linear and the
`Van de Graaff accelerators. The principle of the
`linear accelerator may be followed -from Figure
`21-5. Very high-frequency microwaves (raa.ar)
`collect electrons from a cathode and accelerate
`them as they travel through the vacuum tube,
`reaching almost the speed of light. The electrons
`are emitted and directed to the target at an en(cid:173)
`ergy range of 3 to 15 million electron volts
`(meV). Since energy potentials of 10 meV or
`higher may produce radioactive materials, linear
`accelerators of more than 9 meV are not nor(cid:173)
`mally used for sterilizing.
`The Van de Graaff accele:rators are capable of
`energy potentials up to 3 meV. They utilize the
`force exerted on a charged particle by a high
`voltage potential in an electric field as a means
`of direct particle acceleration.
`Determination of Dosage; The dosage is
`determined by the energy released by the
`gamma rays or by the number of electrons that
`impinge on each square centimeter of absorbing
`substance (the target). The rad is the unit of ab(cid:173)
`sorbed radiation, the unit of dosage now most
`frequently employed. It is arbitrarily defined as
`the absorption of 100 ergs of energy per gram of
`substance. The depth of penetration within a
`target of a given dose is directly related to the
`electron voltage of the source, and indirectly re(cid:173)
`lated to the density of the material to be irradi-
`ated.
`·
`Lethal Action and Dosage. Ionizing radia(cid:173)
`tions destroy microorganisms by stopping repro(cid:173)
`duction as a result of lethal mutations. These
`mutations are brought about by a transfer of ra(cid:173)
`diation beam energies to receptive molecules in
`their path, the direct-hit theory. Mutations also
`may be brought about by indirect action in
`
`FIG. 21-5. Operating principle of a linear electron accel(cid:173)
`erator. (Courtesy of High Voltage Engineering Corp.)
`
`which water molecules are transformed into
`highly energized entities such as hydrogen and
`hydroxyl ions. These, in _tum, bring about en(cid:173)
`ergy changes in nucleic acids and other mole(cid:173)
`cules, thus eliminating their availability for the
`metabolism of the bacterial cell. Ionizing radia(cid:173)
`tions differ from ultraviolet rays in their effects
`on matter primarily in that the former are of a
`higher energy level, ·actually producing ioniza(cid:173)
`tion of constituent atoms. Bacterial spores and
`viruses are generally four to five times more re(cid:173)
`sistant than vegetating bacteria and molds. A
`dose of 2 to 2.5 megarads, however, is consid(cid:173)
`ered adequate. to ensure sterility. 21 Currently,
`there is no evidence of reactivation of microor(cid:173)
`ganisms as has been found with ultraviolet light.
`Applications for Sterilization. Accelerated
`electrons or gamma rays may be used to sterilize
`select products by a continuous process. Most
`other product sterilization procedures must be
`
`STERILIZATION• 629
`
`Novartis Exhibit 2186.008
`Regeneron v. Novartis, IPR2021-00816
`
`

`

`performed in batches. Continuous-process steri(cid:173)
`lization requires exacting control so that there
`are no momentary lapses in sterilizing effective(cid:173)
`ness. Assurance of adequate dose delivery, com(cid:173)
`plete and uniform coverage of the product, and
`adequate penetration have been achieved in the
`effective and routine sterilization of sutures, 22
`using a linear accelerator. Adequate dosage is
`usually determined by the effect of the absorbed
`energy, at the maximum determined depth of
`penetration, on photographic film, and/or on the
`biologic indicator Bacillus pumilus.
`The use of radiation · is increasing in fre(cid:173)
`quency and exterit as experience is gained with
`this method, particularly for the sterilization of
`medical plastic devices. It has been given new
`impetus by the question raised by the Occupa(cid:173)
`tional Safety and Health Administration (OSHA)
`on the safety of ethylene oxide and the low envi(cid:173)
`ronmental level now being permitted. Availabil(cid:173)
`ity of facilities for this method, using both en(cid:173)
`is increasing. An individual
`ergy sources