FIELD T-l 

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relative quantities of the test compound and secondary compound involved] have 

 been felt insufficiently developed and too complex to include in the present 

 edition of the Code. ) 



(2) Additive effect (See Figure 1. ): The intensity of action, when the compounds are 

 administered together, is equal to or not significantly different from the sum of 

 the intensities of action of the two compounds when each was administered 

 separately and in the same dose quantity as when administered with the other. 

 For this, use Symbol C. Example: Consider the example used above to illustrate 

 synergism: If the intensity of response when the two compounds were administered 

 together were 50%, or not significantly greater than or less than 50%, the test 

 compound's influence is interpreted as an additive effect. Note the following 

 special situation and the provision for it: If the intensity of response when the 

 two compounds are administered together is not as great as the sum of the re- 

 sponse intensities when each is administered alone, yet is more than the 

 intensity of response of the compound coded as the secondary compound when 

 administered alone, the CBCC uses Symbol C. In the example used above to 

 illustrate synergism: If the intensity of response when the two compounds 

 administered together were of any degree more than 40% and less than 50%, the 

 CBCC would code in Field T-l the effect or influence of the test compound on 

 the action of the secondary compound as being "additive with the secondary 

 compound", using Symbol C. However, if the intensity of response when the 

 two compounds are administered together is not only less than the sum of the 

 response intensities of each when each is administered alone, but is less than 

 the intensity of response of the compound coded as the secondary compound 

 when administered alone, the CBCC interprets the test compound effect as 

 antagonism (Symbol 9), described below (B, I, [2]). 



II. Actions of the test compound and secondary compound when administered alone are 



NOT KNOWN to be the same (are not known to be the same or opposing) and/or intensity 

 of action of the test compound when administered alone is NOT KNOWN. (See Figures 2 

 and 4. ) 



If the intensity of action of the secondary compound when administered alone is 

 known, and the action of the test compound is known to be the same as the action 

 of the secondary compound (Figure 2) or to be the opposing action (Figure 4), but 

 the intensity of action of the test compound is unknown (both Figures 2 and 4), it 

 can not be determined, when the intensity of response to the secondary compound 

 is enhanced, if the influence of the test compound is synergistic or merely 

 additive. In such cases (when the intensity of response to the secondary compound 

 is enhanced), the CBCC has established the convention of coding Field T-l with 

 Symbol C; i. e. , treating the data as additive. Under these circumstances, the 

 written abstract should make clear in Field T- 1 that the test compound's being 

 additive or synergistic has not been determined: If only one word is written in 

 Field T-l, it should be "increase", rather than "additive", even though Symbol C 

 is entered in the code box. 



Evaluation of additive effect: When a code line is constructed for recording 

 specifically the fact that the two compounds administered together produce a 

 response that is additive (i. e. , one compound does not synergize or antagonize 

 the action of the other), there is a peculiar problem of evaluation in Field Y, 

 since the quality of "additiveness" can scarcely be described in degree. Only 

 Criterion 01 can be used in Field X when Field T- 1 is coded with Symbol C. 

 However, because of the special provision, described in I (2) above, for using 

 Symbol C under circumstances when the intensity of response to both compounds 

 administered together is to a limited degree less than precisely additive, Field Y 

 is coded in the following various ways: When the results are exactly additive 

 (i. e. , an actual additive effect; for example, 50% in the illustration of A, I, [2]), 

 it is indicated in Field Y by using Symbol 9 (Symbol C in Field T-l). On the 

 other hand, if the response when the two compounds are administered together 

 is only slightly more than the response of the most active of the compounds when 



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