Currently, Sensexa causes the subject to feel pleasure, and Nul-Sensexa causes the subject to feel pain.
Instead, have Nul-Sensexa make it harder for the subject to feel pleasure[and nullify the effects of any Sensexa in their body], and make an additional chemical/nul-chemical pair for causing/inhibiting pain.
Use case: You accidentally overdosed your subject on Sensexa, and wish to nullify the excess. However, currently the only way to do so is to use Nulriset, which will also nullify any other chemicals in their body, which you might not want.
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