counteractant

例句：

1. 1. The newdrug counteracts the effects of the old medication.
   这种新药可以抵消旧药物的效果。
2. 2. The doctor prescribed a special antibiotic to treat her infection.
   医生开了一种特别的抗生素来治疗她的感染。
3. 3. The bacteria that cause the infection are resistant to the antibiotic agent.
   引起感染的细菌对抗生素有抗药性。