One of the main weapons to prevent mother-to-child transmission of the AIDS virus during birth is the drug nevirapine3. But when nevirapine is used alone just once, HIV4 starts becoming resistant to it. Research in Botswana shows that the resistance is not long lasting and that this affordable drug does not have to be abandoned forever by infected mothers who have already taken it.
International medical guidelines call for5 pregnant women with advanced HIV to get a combination of AIDS drugs including nevirapine to prevent passing their infection on to their newborns during delivery. But in poor countries, combinations have been expensive and nevirapine has often been Used al. one, since studies have shown that a single dose can cut the transmission rate in half.
The problem is that HIV resistance builds against it quickly when used alone just once because other drugs are not present to kill the virus particles that survive nevirapine. This renders the drug less effective in later combinations for treating women after their baby is born. But the new study from Botswana shows that nevirapine can make a comeback for these women if they wait until the resistance subsides.
“The further out you get from that exposure to single dose nevirapine, the less detectable nevirapine resistance is6,” said Shahin Lockman of the Harvard School of Public Health in Boston7. She says waiting period for women who get the single dose of nevirapine at delivery can be as short as six months. “If they started nevirapine-based treatment six or more months after nevirapine exposure, their treatment response8 was just as good, and really quite high, compared to women who did not have the single dose of nevirapine,” she added. “However, the women who started nevirapine-based treatment within six months of that nevirapine exposure were much more likely to experience treatment failure.”
The study published in the New England Journal oJ Medicine9 shows that waiting at least six months means that HIV-positive women are 70 percent more likely to benefit from nevirapine-based drug combinations again than women who get them sooner. An official with the U.S. government health agency that helped fund the study calls it very important.
I.ynne Mofenson is chief of research on child, adolescent, and maternal AIDS at the U. S. National Institute of Child Health and Human Development10. She says the finding supports a World Health Organization (WHO)H recommendation restricting a single dose of nevirapine only to pregnant HIV-infected women who are healthy enough to wait six months after childbirth for more nevirapine-based therapy. Otherwise, they should get other drugs during labor. “It shows the importance of screening women for treatment while they are pregnant and putting them on appropriate therapy while they are pregnant to avoid having to start them too soon after they received preventive therapy,” she explained.
Shahin Lockman in Boston says the problem of nevirapine resistance should diminish now that12 more and more people are receiving combinations of AIDS drugs under expanded U. S. and international programs to deliver them to Africa and other regions hard hit by the virus.
练习:
1. What effect does nevirapine have?
A. It is a broad-spectrum antibiotic and kills all kinds of bacteria.
B. It is an antiviral preparation and kills all kinds of viruses.
C. It prevents the transmission of the AIDS virus and protects one from heart attack.
D. It may prevent passing HIV infection from mothers on to their newborns during delivery.
2. Why does HIV resistance against nevirapine build very quickly even when the drug is used alone just once?
A. Because the drug is not strong enough to kill all of the HIV in the body.
B. Because there may not be a susceptibility test before using the drug.
C. Because other drugs are not present to kill the virus particles that survive nevirapine.
D. Because there are too many mutations of HIV for nevirapine to deal with.
3. When may a woman start her nevirapine-based treatment if she gets the single dose of nevirapine at delivery ?
A. She may start nevirapine-based treatment soon after her delivery.
B. She may start nevirapine-based treatment within six months after her delivery.
C. She has to wait at least six months after that nevirapine exposure.
D. She may wait several years so as to achieve the best effect.
4. We may learn from this passage that HIV resistance against nevirapine
A. lasts only for about a half year and fades quickly.
B. will last forever in a woman who took nevirapine.
C. is a terrible drug that must be banned at once.
D. is a problem too difficult to be solved.
5. Generally speaking, the author's attitude towards the use of nevirapine is
A. negative
B. positive
C. uncertain
D. doubtful
答案与题解:
1.D 第一段第一句及第二段第二句均提到nevirapine可以防止母亲在分娩时将HIV病毒传染给新生儿的问题,故D项是正确答案。
2.C 第三段第一句说,即使单独使用nevirapine一次,HIV病毒也会很快产生对nevirapine的抗药性,原因就是没有其他药物可以杀死nevirapine还没有杀死的病毒颗粒,这正是C项的内容。
3.C 第四段第二句说到,等待的时间最短可到六个月,第五段第一句又说,最少等待六个月的妇女,她们以nevirapine为主的药物综合治疗的疗效要比等待不足六个月的妇女高70%,可见C项“最少要等待六个月”是正确答案。
4.A 第一段第三句说到抗药性存在的时间并不长,第四段第二句又说等待的时间可以短至六个月,另外,文章的标题也说抗药性很快消失,可见A项是正确选项,其他各项文章均未提及。
5.B 第一段是文章的提要,最能说明作者观点,其中最后一句就明确提到,已经服用 nevirapine的已感染上HIV的母亲们不应该放弃服用这种能用得起的药物。而且通篇文章都在探讨如何更有效地利用此药物,因此作者对使用此药的态度应该是“积极的、肯定的”。
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