试述磺胺类药与甲氧苄啶（TMP）合用的意义与机制。
参考答案：
TMP的主要机制是抑制二氢叶酸还原酶，阻断叶酸合成，从而影响细菌的生长繁殖，而磺胺药能抑制二氢叶酸合成酶，故两者合用，分别阻断叶酸代谢的不同环节，呈双重阻断作用，作用增强数倍至数十倍，且降低抗药性并减少用药剂量。SMZ与TMP两药药动学特点相似，便于保持血浓高峰一致，发挥协同抗菌作用。故常两者合用。
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| I have had thousands of classes since I started school nine years ago. But only one 1 was the most important. It happened last term just after I had got a 2 result in an exam. I was sad and had lost my confidence. I decided to go to a class which can tell me how to be 3 . The speaker walked into the room. But he did not start talking 4 a teacher. Instead, he held up a twenty yuan note! "Who wants this?" he asked. Unsurprisingly, 5 of us in the class put up our hands. The speaker smiled. Then he put up the note on the blackboard and asked the same question. Again, we all put up our hands. The speaker smiled again, but 6 nothing. Suddenly, he threw the note onto the floor! Then he asked the same 7 a third time. I didn't 8 what the speaker was doing. Why was he asking the same question again and again? I didn't know what to do. I wanted the note, 9 I put my hand up again. After a while, he 10 the note and started to laugh. "You have all just told me how to become successful," 11 said to us with the note in his hand. "The note is worth (值) twenty yuan. It is 12 worth twenty yuan, even though I throw it on the floor. You are like the note. No matter 13 happens to you, you still have your worth." When I heard those words, I was deeply moved. Suddenly, I 14 I was worth a lot. I may have done badly in an exam, but it doesn't 15 I can't do well in the future. If I believe in myself, I will be successful.
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