Vol. 4 - I982
Pharmaceutisch Weekblad Scientific Edition
49
A new approach to stei'itization conditions. The I M O concept J.
VAN
ASTEN 1
AND
J.W.
DORPEMA 1
on the material (Propper Manufacturing Co., Inc. I98O; Ph.. N e d . 1978 ). However, it proved to be impossible to confirm the absolute absence of microorganisms, so a more realistic definition was formulated; out of a batch of one million items a maximum of one item inay remain contaminated aftersterilization (Propper Manufacturing Co., Inc. I98O; BROWN and GILBERT I977). Even to prove sterility, in view of this last definition, by post-sterilization sampling (i.e. final product testing) requires unrealistically large numbers of samples. For example: to prove with 95% accuracy that any batch - independent of its size - is sterile according to the last definition, would according to the Poisson distribution - take three million samples (Report of the Working G r o u p on Sterilizing Dose 1976; SPICHER I973; WHO I973). A solution for this problem was found in the Fo theory, in which the last definition is incorporated (AKERS I979; AKERSet al. 1978; DORPEMAand TOLMAN I980; HOSKINS and DIFFEY I978; KORCZYNSKI I 9 8 0 ; INTRODUCTION Ever since sterilization was first regulated the LEE et al. 1979). Using the Fo theory, however, introsteam sterilization requirements have been based on duced quite a different problem; the initial contamination of the load should .be determined. This Bacillus s t e a r o t h e r m o p h i l u s . This provided two sterilization t i m e - t e m p e r a t u r e combinations i.e. 20 min problem limited the application of the Fo theory to at 12o~ or 3 rain at I34~ (common accepted re- only a few sophisticated users. This paper provides the means to use the Fo theory quirements). It should be emphasized that an exteneven without ~he determination of the initial contamisive overkill was incorporated in these requirements. Through the years, as more thermolabile products nation. For this purpose the F0 theory has been were introduced, the need for less destructive steril- extended and as a consequence an Imaginary MicroOrganism 0MO) was created. By means of this IMO ization conditions became apparent. Concurrently biological indicators have been the concept the commonly accepted requirements can subject of extensive studies. In many studies their be transformed to any temperature or time selected~ inaccuracy was shown (ANDERSON and FRIESEN 1"974; thus avoiding any 'guesswork'. Moreover, a strategy BOWMAN 1969; CAPUTOet al. 1979, 198o; COSTIN and has been developed to obtain even more favourable GRICO I974; DOBBERKAU et al. I980; DORPEMA and sterilization conditions if the initial contamination determination is not entirely omitted. Finally - using TOLMAN 1980; FRANCHI and LENCIONI 1978; HALLECK et al. I979; HODGESet al. 198o; KELSEY I958, 1961; the IMO concept -- a mathematical linkage between KERELUK 1976; LEE et al. 1979; LUMINI et al. 1978; microbiological and physical parameters has been REICH et al. 1979; SCHRAMM and SCHMIDT I974; SEV- formulated. The effectiveness of a sterilization proFARTH 1975; SMITH et al. 1976; SPICHER and PETERS cess can thereby be determined on physical instead 1978; TJOENG and DE FLINES 1979; TOLMAN and DOR- of on bacteriological indicators. The same mathematical linkage can be used as a P E M A 1980; WOLFF 1975). This has been one of the main reasons for adopting a tendency - noticed all basis for the switch from process monitoring to proover i n d u s t r y - t o change from process monitoring to cess control. The IMOconcept introduces a strategy to process control. In sterilization technology process develop or improve the process control even w h e n control should be thought of as guarding the cir- only part of its contents is adopted. cumstances leading to sterility, with respect to the characteristics of the process (BOWIE 1955; HOSKINS and DIFFEY I978; Parenteral Drug Association 1978; C H A R A C T E R I S T I C S The characteristics which are involved in the evolSELMAN and HIGNETT 1979). Originally sterilization had been defined as: treat- ution of the IMO concept are partly micro-organism ing contaminated material in such a way that after related (k, D and z), and partly bioburden or process treatment no living micro-organism is present in or related (No, F and L). ABSTRACT
The sterilization requirements for medical/pharmaceuti.: cal applications are traditionally based on an extensive overkill. In the past few years, however, an evolution towards bioburden related sterilization processes has been started (Fo theory). Especially manufacturers of large volume parenterals have - forced by the thermolability of the product - contributed to this development. In this paper both philosophies are combined, resulting in a concept in which the bacteriological and physical bases of the sterilization process are mathematically related by using the Fo theory and by introducing an Imaginary Micro-Organism (IMO). The tMO concept provides the opportunity for anyone in the field of sterilization to raise the quality control level, which can be achieved by: selecting optimum sterilization conditions without performing pre-sterilization counts; -step by step introducing the pre-sterilization count which results in even more favourable sterilization conditions. (Pharm. Weekbl. Sci. Ed. 4, 49-56)
t Rijksinstituut voor de Volksgezondheid, P.O. Box I, 3720 BA Bilthoven, The Netherlands.
Vol. 4 - 1982 Pharmaceutisch Weekblad Scientific Edition
50
k- Value The n u m b e r of micro-organisms to die in a sterilization process will depend on the n u m b e r of microorganisms present: dN/dt = - kN
(eq. ])
with N = n u m b e r of organisms; k = a micro-organism and its e n v i r o n m e n t d e p e n d e n t constant; t = time interval. Integration will give: t=h t=h .fdN = - J ' k . N . d t t=o t=o N t l = Nt=o.e -kt
(eq. 2)
with Nt=o -- No = pre-sterilization micro-organism count; Nt~ = micro-organism count after sterilization for tl minutes, or logarithmically: lnNtl-lnNo
kD/2.3o3 = I; D = 2.3o3/k
=-ktl
kh/2.3o3 = log'No - log Ntl
D e c i m a l reduction (decimation) time The time required to reduce the n u m b e r of microorganisms with a factor IO is called the decimal reduction or decimation time D (Fig. 1). The D-value of a micro-organism species is d e p e n d e n t on intrinsic (i.e. genetic characteristics) and extrinsic proporties (i.e. culture conditions) and environmental factors during sterilization. It is possible to m a nipulate D - v a l u e s experimentally by changing the composition of (pre)culture media. If for example a sterilization process has a sterilization time of 20 min at a given t e m p e r a t u r e (say I2o~ and the micro-organisms to be killed have a D-value of 2 min the micro-organism count will be reduced with a factor zo 1~Le. from ]o j~ m i c r o - o r g a n isms m a x i m u m one will be left. Relating the definition of the decimation time with equation 3 gives:
(eq. 3)
(eq. 4)
C o m m o n practice is to use D and not k as a micro-organism characteristic (BOOM and PAALMAN ]979; FRIEBEN et al. I978; KORCZYNSKIet al. 1974; MIKOLAJCIK atld RA~rOWSKX 1980; Parenteral Drug Association 1978; SRIMANI and LONCIN ]980; RIV ]980).
Each combination of micro-organism and sterilization process has its own k-value which can be determined by varying the sterilization time tl and determining the micro-organism count afterwards. Since k has a constant value a logarithmic plot of Initial contamination (bioburden) The initial contamination is the n u m b e r and N(t) vs t will result in a straight line (Fig. ] )..It is still a species of micro-organisms present in or on an item matter of discussion if deviations of this curve (the before sterilization (pre-sterilization count) (ROOM so-called sho.uldering or tailing p h e n o m e n a ) can be exclusively attributed to experimental "conditions and PAALMAN 1979; MYERS 1978; Parenteral D r u g (ALDERTON and SNELL ~963, 1969; COOK and GILBERT Association 1978). The initial contamination is a key factor in calculating the sterilization dose (here 1968a, b; COOK ~nd BROWN ]965; DOBBERKAU et al. 1980; DORPEMA and TOLMAN ]980; FINLEY and FIELDS t i m e - t e m p e r a t u r e combination). If e.g. the pre-sterilization count shows that in a lot ]962; MARSHALLand MURRELL ]970; WYATr and WAITES 1975) or must be classified as experimental evi- of say io 7 items the biological load per item is ~< IOO and that most ( > 95 % ) of the micro-organisms are B. dence (CERF ]977; nAN ]975). subtilis a reliable sterilization time can easily be calculated. A m a x i m u m of ]0 -6 x 1o7 = IO items may be found to be nonsterile after sterilization (the faclog N t l tor 1o -6 is the previously mentioned extended ster1 ility requiremenf). The only way to be sure that no 8 m o r e than io items are c o n t a m i n a t e d is to suppose t h a t e a c h micro-organism is on a different item, re7 suiting i d a m a x i m u m of IO micro-organisms to survive. 15 The D-value ofB. subtilis (spores) for steam steril5 ization a t [ 2o~ is 0. 5 min (CAPUTOet al. ] 979; HOOGES et al. ]980; Parenteral D r u g Association I978; 4 SRIMANI and LONCIN 1980; WALLH,~USSER ]980) and the total micro-organism count is ]oo x io 7 -- 1o 9. 3 Reducing io 9 to 1o will require a sterilization time of 8 x D i . e . t = 8 x D = 8 x 0.5 = 4 m i n . d In a general formula: 1
t = D (log No per item -- log ]O-6) ~D~
~tl
FIGURE I. N is logarithmically plotted against time to determine the D-value
t = D (log No per item "l- 6 ) In our example: t = 0. 5 x 0.5 x (2 + 6) = 4.
(eq. 5) (log ]oo + 6) =
Vol. 4 - t982
Pharmaceutisch Weekblad Sciennfic Edition
A reliable pre-sterilization count in combination with the correct D-values will lead to an o p t i m u m sterilization process. However, up to now the policy has been to choose relatively high D- and No-values, introducing an extra overkill (KERELUK i976; KORCZYNSKI et al. 197,~). Resistance coefficient The resistance coefficient (z) of a micro-organism is a measure to indicate the change in heat resistance as a result of a change in t e m p e r a t u r e (or e.g. gas sensitivity as a result of concentration changes) (BOOMand PAALMAN 1979; FRIEBENet al. 1978; KORCZYNSKI 1980; KORCZYNSKI et al. t974)- The z-value for steam sterilization has been defined as the n u m ber of degrees t e m p e r a t u r e change required to increase D with a factor Io. The z-value is essential in comparing steam sterilization processes at different temperatures. The z for a micro-organism is calculated from a n u m b e r of D-values which are determined at different t e m peratures. These D-values are logarithmically plotted against t e m p e r a t u r e (Fig. 2). F r o m this plot z can be calculated: z = I / t a n a = (T2-T1)/(Iog D~-log D2)
(eq. 6)
51 therefore often printed with the F-value and the temperature, as one symbol: lO
FL20 = 20 ( = Fo)
A process corresponding to this example will result in a micro-organism killing which is equal to the killing (with a i0 -6 chance on survival) of micro-organisms with a z-value of to in a sterilization process at x20~ for 20 min (AKERSt979; BOOM and PAALMAN 1979; FRIEBENet aL I978; HOSKINS t979; HOSKINSand DIFFEY 1978; KORCZYNSKI 1980; LEE et al. t 979; MYERS I978; Parenteral Drug Association 1978 ). Reduction factor The n u m b e r of times the decimation time D is reached in a sterilization process is called the reduction factor (n): F=n.D with: F = the calculated sterilization time at a given t e m p e r a t u r e ; D = the decimation time at that temperature. If two processes are supposed to have equal efficacy, their reduction factors will be the same. If T2 > T t then DI > D2, so FI = n.Dt
If D~ = IOD2. z = T2-T~.
F2 = n.D2 F-value At every t e m p e r a t u r e the sterilization process has a certain killing effect. To convert the killing effectivity at different t e m p e r a t u r e s to a reference temperature F has been introduced. The F-value of a steam sterilization process at a given t e m p e r a t u r e is the time needed at that t e m p e r a ture to create a "killing effect' similar to that of a standard sterilization process (t-in equation 5 is an F-value). C o m p a r i n g the micro-organism killing effect the only key factor is the z-value. The z-value is log D
) 4
F~/F2 = DI/D2 z = l/tan a = ( T 2 - T l ) / ( l o g D~-log D2) log D ~ - l o g D2 = 10g (Di/D2) = (T_,-T~)/z 9 Ft/F2 = DI/D2 = lO (T'--T')/z El :
F2 x IO (Tz-TzVz
(eq. 7)
Total lethality The total killing effect during a sterilization process can be calculated by adding all killing effects per time interval created at the different t e m p e r a t u r e s reached in the process. The lethality is the killing effect per time interval (related to the reference value Fo) (BOOM and PAALMAN 1979; KORCZYNSKI t980): L = I/F.
In o t h e r words, the killing effect of L x Fo minutes at l zo~ is the same as the killing effect of one minute at the t e m p e r a t u r e on which L has been determined. The total lethality has been defined as:
D1 3 I
k..d ZLAt ~ta,
D 2 ,z
1
k..d = fLdt t~ta,
(eq. 8)
By combining the equations 5 and 7, the F-value for steam sterilization at a given t e m p e r a t u r e (Ti)can be calculated: TI
Z
T2
~
T
FIGURE 2. D-values are logarithmically plotted against temperature to determine the z-value
Fi -----Dst (log No - log Io -6) Io ('I'~'--'l'i)/~'dl
(eq. 9)
where Dst, Wst and zst are the micro-organism charac-
52
Vol. 4 - I982
teristics with r e s p e c t t o the standard process and E is the F-value to be calculated in relation to the given temperature. From these F-values the lethality (killing effect contribution to the total lethality) at any temperature can be calculated. W h e n e v e r the total lethality becomes > I sterilization is completed. D E C I D I N G ON N o - , D STEAM S T E R I L I Z A T I O N
AND
Z-VALUES
Pharmaceutisch Weekblad Scientific Edition
F l /
~5
....
B. s t e a r o t h e r m o p h i l u s B. subtilis
FOR
The theory explained above is only applicable if proper micro-organism characteristics are available. There are several ways to determine these values.
10
The actual initial contamination & determined and the real No, D- a n d z-values are calculated
The methods used at present to determine the real initial contamination require special training, facilities and equipment. Holding on to the actual initial contamination as a basis for all calculations limits the 5 applicability of the'total lethality principle to only a few suitably equipped (in man and material) institutions (AKERS et al. 1978; BURRELLet al. 1979; CAPUTO et al. I979, I980; FRIEBEN et al. 1978; KORCZYNSKI I980; MYERS 1978 ). Although the use of the actual 2 initial contamination would provide the greatest benefit of the principle, several less complicated 1 approaches are available. 0.5 o
~t
1;o
12o
A suitable hz#ial contamination & selected .
The current" sterilization requirements are based on the fact that a population of IO6 B. stearothermophilus (spores) must be 'entirely' killed in .the process (AKERS et al. I978; BARBEITO and aROOKEY I976; DORPEMA and TOLMAN I980; Propper Manufacturing Co., Inc. 198o; RIV I980; TOLMAN and DORPEMA 1980; Association for the Advancement of Medical Instrumentation i98o; D e p a r t m e n t of Health and Social Security i98o ). The way this requirement was phrased in the past is equal to the present requirement that out of a lot of I million items only one may be found to be nonsterile (for this purpose a B. stearothermophilus is considered an item ke. No = I). An extra overkill has been introduced by adding 50% (6 min) to the calculated time thus introducing the current sterilization requirement: 18 min at I2I.I~ or (as used in for instance The Netherlands) 2o rain at i2o~ At 12 i. I ~ D B..........., ........ phiht, 2 and z = 6 (AN=
DERSON aI:lE] FRIESEN ] 9 7 4 ; KELSEY I 9 5 8 ; MIKOLAJCIK and RAJKOWSKI I980; REICHet al. [979; SRIMANI and
LONCIN I980; WALLH,~USSER I980 ) resulting in F = 12 min IF = D(log No + 6)1o 'T.-T:)' = 2(0 + 6)IO (':' '-':'-'"{' = 12]. The 18 rain at ]21.]~ requirement can also be formulated as the time needed to kill not to 6 but 1o9 B. stearothermophilus (or No is not I but 1o3). Choosing B. stearothermophilus (spores) as a standard for the theory has several disadvantages: - B. stearothermophilus is very rarely present in the
I
1s0
13o ,-
temperature
FIGURE 3" T h e r m a l d e a t h curves o f B. subtilisand B. stearothermophi/us, s h o w i n g B. subti/is to be the m o r e resistant one at t e m p e r a t u r e o v e r I29~
bioburden in a medical/pharmaceutical environment (AKERS 1979; BEAL 1980; BECK 1978; FLEMING et al. I980; HORAKOVA and BURIANKOVA I974; IRVING 198o; KEOGHand HOPKINS 1973; KONOLDet al. 1974; LIM 1979; MELICHARet al. I980; SINATRA and GIANNALIA I98O); - B. stearotherm, ophilus is (calculated from literature values) not the most heat resistant micro-or.ganism over the entire temperature range. Accordlng to 9)ur calculations B. subtilis is more resistant at temperatures over I29~ (Fig. 3); - The F-values for B. stearothermophilus are not applicable under or over a temperature of I 18~ or 135~ respectively, for sterilization times would become unrealistically long respectively short [43 088 and 0.0002 min respectively at loo~ and [5o~ (No = I)]. An alternative micro-organism to choose would be B. subtilis (D = 0. 5, z = IO) (CAPUTO et al. I979; HODGES et al. t98o; Parenteral Drug Association 1978; SRIMANI and LONCIN t980; WALLH~,USSER1980) which is the most frequently observed sporeforming micro-organism in medical/pharmaceutical environments. B. subtilis is more heat resistant than most other micro=organisms and F-values are re-
Vol. 4 - 1982
53
Pharmaceutisch Weekhlad Scientific Edition
TABLEI. D- and z-values o f some representative micro-organisms ( Wallhiiuser I98o) Name
D (I2I~
Z
Clostridium botulinum Bacillus stearothermophilus (spores) Bacillus subtilis Bacillus megaterium Bacillus cereus Clostridium sporogenes Clostridium histolyticum
o.2o4 2.0 0.5 0.04 0.007
lo 6' Io 7 Io
o.8-1.4 o.o I
13 lO
alistic (CAPUTO et aL I979; HODGESet al. 198o; COSTIN and GRICO I974; KELSEY I958; PULEOet al. I975), cf. Figure 3. However, using B. subtilis as a basis for the concept would lead to diminishing the overkill introduced by the high D - v a l u e - as B. stearothermophilus has - and the 50% added to the minimum. In a well controlled production process where the micro-organisms present are known to be less resistant then B. subtilis (i.e. vegetative germs) and the pre-sterilization count is determined, the values for B. subtilis could be used. The advantage of using the B. subtilis values is that it does not require an exact determination of the species, but can be restricted to an exact numerical count to determine the No-value to be used in combination with the D- and z-values of B. subtilis. UsingB. subtilis values as bases will therefore not solve the entire pre-sterilization count problem but only the most complicated part of it.
0 iS
--
IMO
. . . . . . B. subtilis -- - - B. stearothermophilus
500t~
250 ~,,
loo
\
,,
50
0
...
9
100 108110 120
130
140
150 9 temperature
FIGURE 4- C a l c u l a t e d iMo-values and t h e r m a l death curves
of 1ooo B. subtilb and IOOOB. stearothermophilus t h e r m o p h i l u s (curve l),.IOOO B. subtilis (curve 2) and
IMO (curve 3) are plotted in Figure 4.
The origin o f the I M O concept
The only way to avoid the pre-sterilization count completely but still be able to practice the theory, will be using the characteristics of a micro-organism that obeys the currently accepted requirements exactly (i.e. IO6 of these micro-organisms will die in 20 min at I2o~ or in 3 min at I34~ Unfortunately such a micro-organism does not exist. We therefore defined and set an Imaginary Micro-Organism (IMO) to fulfil these requirements. The characteristics of the IMO can be calculated by substituting the requirements in equation 9 and solving the resulting two equations. This will give the following values (calculated at 12o~ D = 3.33;
z=
I7
To be able to think of IMO as a micro-organism No is postulated I (as with B. stearothermophilus). From Table I it can be seen that the IMO D- and z-values have a safety margin incorporated in them. The high z-value will slow down the decrease in sterilization time at temperatures over i2o~ by keeping the exponential term low. Since the F-values of the IMO are based on the current requirements, they have the same sterility assurance as the current requirements and (like the current requirements) can be used without any presterilization count. The F-values for iooo B. stearo-
APPLICABILITY OF THE CHARACTERISTICS, SO'ME EXAMPLES A lot of applications are conceivable and several of them are at the moment under investigation (e.g. comparing totally different sterilization processes or comparing wrapping material for hospital sterilization). The following applications are already practised. Calculating the total lethality after sterilization is completed, will give an indication of the quality of the sterilization process (process monitoring) (BROWN and GILBERT 1977; BURRELLet aL I979; EVERALL and MORRIS I975; SMITH et al. I976). Using F~Mo-values for this calculation will give a quality indication with respect to the current sterilization requirements. Using the characteristics of, the actual bioburden will give an indication on the quality of the process with respect to the microorganisms to be killed. Using equation 9 and the IMO characteristics, any t i m e - t e m p e r a t u r e combination which will give a sterility assurance equal to the current requirements, can be calculated. These F-values over a temperature range of IOO-I5o~ are listed in Table n. - Sterilization processes can be controlled in such a
-
-
54
Vol. 4 - x982 Pharmaceutisch Weekblad Scientific Edition
TABLE II. Times to stedlize at given temperatures (FIMovalues) Temperature
min
Temperature
mm
IOO io! 102 I03 104 105 ~06 I07 108 IO9 IO II 12 ~3 14 I5 16 17 18 I9 12o 121 122 123 I24 125
300.257 262.223 229.006 199.997 I74.663 152.538 133.215 116.340 101.603 88.7326 77.4925 67.6762 59.1o35 5L6166 45.o781 39.3679 34.3811 30.0259 26.2224 22.9007 19.9998 17.4664 15.2538 13.32X6 Xl.6341 10.1603
126 127 128 129 I30 I31 132 133 I34 135 136 I37 138 139 x4o 14I 142 143 144 I45 I46 147 148 149 150
8.87330 7.74929 6.76766 5.91038 5.16169 4.50784 3-93681 3.43812 3.00260
2.62225 2.29008 1.99999 1.74664 1.52539 1.33216 I.]6341 x.oI6o4 0.887335 0.774933 0.676769 o.59io4i o.516171 0.450786 0.393683 0.343814
way that the total lethality is ~ ~ before the sterilization phase is stopped and drying of the goods starts. Suppose one is not able to do a good pre-sterilization count (so IMO-values have to be used) and that the sterilization process has the simple t e m p e r a t u r e profile as shown in Figure 5. For t e m p e r a t u r e s below io8~ FIMO > Ioo: the lethality contribution is less than t % . These lethality contributions are negligible and o n l y ' t e m peratures o v e r lo8~ are supposed to contribute. Calculation starts after lo8~ has been reached (tstart).
In the first minute the t e m p e r a t u r e rises to i ]2~ the average t e m p e r a t u r e Tar is I lo~ and FIMO at l Io~ is 77.5. The contribution to the total lethality T~rt
~C
116 112
108
t (s~rt)
t tend)
~
FIGURE5" A simplified sterilization process of which the total lethality can easily be calculated
t
in this minute will be 1/77.5. In the second minute t e m p e r a t u r e rises to I I6~ Tar = I14~ FIMO = 45 and the contribution is I/45. When the sum of all contributions (total lethality) reaches i the sterilization phase can be stopped. In the cooling period an extra killing effect is introduced. In a well known process the contribution of the cooling period to the total lethality can be predicted and used in the calculation of the sterilization time. In this example the time interval on which the t e m perature is measured is i min. If, for example, seconds were to be used the F-values (which are based on minutes) should be multiplied by 60. In c o - o p e r a t i o n with the Rijksinstituut v o o r de Volksgezondheid (National Institute of Public Health) several manufacturers of sterilizers have already built steam sterilizers which are controlled according to the IMO concept. PERFORMANCE
STATE
In our opinion the application of the IMO concept or one of its alternatives (as s u m m a r i z e d above) will depend on the p e r f o r m a n c e state of the user. At this m o m e n t five different p e r f o r m a n c e states can be distinguished. o. In this p e r f o r m a n c e state no effort is made to improve process control, and there is therefore no valid basis to allow any o t h e r t i m e - t e m p e r a ture combinations than the current 2o min at I2o~ and 3 rain at x34~ (RW I980; Ph. Ned. 1978). 1. The principles of the sterilization process and the uao concept are explored. The actual bioburden is not d e t e r m i n e d but checks are occasionally done. T h e IMO-values can be used to choose any t i m e - t e m p e r a t u r e combination or to control a sterilization process, thus avoiding the 'at rand o m ' choice of times to sterilize at a given t e m perature. 2. Pre-sterilization count has been limited to determining the n u m b e r of micro-organisms. If the n u m b e r shows to be rather low ( < < I o o o ) the current r e q u i r e m e n t of 20 rain at 120~ may be considered excessive (see above) and a substitute r e q u i r e m e n t can be considered. From this an alternative IMO 0MOX) can be calculated. The Fluox-values are to be used as the FtMo-values are in.performance state I. A range oftMox-curves (based on 20 min at 120~ to 2 min at x20~ are plotted in Figure 6. 5. The numerical pre-sterilization count is performed and the micro-organisms are proved to be less resistant than B. subtilis (i.e. vegetative germs). In this case the actual n u m b e r of micro-organisms and the characteristics of B. subtilis can be used instead of the XMo-values. 4. The actual bioburden and its characteristics are determined. In this p e r f o r m a n c e state there is no reason not to use the approach described in this publication in-its o p t i m u m form i.e. using the real
Vol. 4 - 1982 Pharmaceut&ch Weekblad Scientific Edition
F
B
J
55 2o, 626-629; Ibidem (1968b) J. Fooil Technol. 3, 295-3o2. COSTIN, I.D., and J. GRICO(I974)Zentr. Bakteriol. Parasitenk., Abt. 1 Orig. A 22 7, 483-521. Department of Health and Social Security (198o) Health Technical Memorandum, nr. to. London. DOBBERKAU, H.J., E. $TEIGER and M. NAGEL (198o) Z, Ges. Hyg. 26, 717-721. DORPEMA, J.W., and A.S. TOLMAN (I980) Pharm. Weekbl. *x5, 149~155. EVERALL, P.H., and C.A. MORRIS(I975) J. Clin. Pathol. 28, 664-669. FINLEY, N., and M.L. FIELDS (I962) Appl. Microbiol. to, 231-236. FLEMING, C.R., D.J. WITZKE and R.W. BEART (1980) Ann.
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Vol. 4 - 1982 Pharmaceutisch Weekblad Scientific Edition
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ABSTRACTS
OF
DUTCH
PH.D.
Received S e p t e m b e r 198I. Accepted for publication March 1982.
THESES
Under this heading abstracts will be published of doctoral dissertations that are of interest for the pharmaceutical sciences and are submitted to Dutch universities, or to foreign universities by Dutch pharmacists. Abstracts should be submitted by hTvitation only.
The lower third molar and anti-inflammatory drugs Effects of betamethasone, ibuprofen, indomethacin, naproxen, niflumic acid, oxyphenylbutazone, tranexamic acid and glafenine on the patient's condition after surgical removal of a lower third molar J. VAN DER ZWAN j, University of Groningen, D e c e m b e r 17, I98o Promoters: Prof. Dr. G. BOERING(Groningen) and Prof. Dr. H. WESSELING(Groningen) Referee: Dr. C.TH. SMtTSIBINGA(Groningen) Co-referee: L.TH.VAN DER WEELE(Groningen) A multidisciplinary, double blind, parallel, placebo controlled investigation was made to find. an effective anti-inflammatory drug which prevents postoperative swelling, trismus and a general feeling of malaise. An additional aim was to evaluate objectively the anti-inflammatory properties of antirheumatics. In 126 healthy patients, who were without complaints, the lower third molar was surgically removed. A drug had to be taken orally according to a fixed scheme during four days. Glafenine had to be taken in cas~of pain; the number of tablets taken was used to quantify pain. Swelling of the cheek was measured photographically and trismus was deducible from the maximal mouth-opening. Investigated were betamethasone 14.5 mg decreasing in 4 days, ibuprofen 12oo mg/day, indomethacin 15o mg/day, naproxen 750 mg/day, niflumic acid IOOO mg/day, oxyphenylbutazone 600 mg/day and tranexamic acid 2000 mg/day. Only oxyphenylbutazone and tranexamic acid are
not significantly different from placebo in pain-killing. Only betamethasone prevents swelling and trismus significantly more than the placebo. Betamethasone distinguishes itself significantly from the other drugs concerning prevention of swelling. Reduction of the swelling by antirheumatics may be 1o-15% apd a 2OtYo reduction of trismus is to be expected.-"I'he strongest analgesic is niflumic acid. Tranexamic acid may perhaps reduce the swelling by 28%. The quegtionnaire and the blood- and urine-test showed that antirheumatics have to be considered to be acetylsalicylic acid-like drugs. The literature mentions even serious side-effects. When taken for a short time corticosteroids are very safe drugs with few side-effects, never serious ones. Many patients experience a slight euphoria. Betamethasone, in a dosage of 14.5 mg decreasingly divided over four days prevents pain with 8o%, swelling with 65% and trismus with 4o% compared with the placebo group. This safe drug is r e c o m m e n d e d in elective surgery.
~University Hospital, Department of Oral Surgery, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands.