年輕女孩能安全的使用緊急避孕


  Nov. 18, 2003 (舊金山)--緊急避孕對於年輕女孩是安全的且耐受性良好,這種藥物以前從未在年少年女孩的族群中試驗過,研究人員於星期一在舊金山舉辦的美國公共衛生協會年會上發表這些研究結果。
  
  研究作者,舊金山加州大學的產科醫學及婦科學助理教授Cynthia Harper博士在接受Medscape訪問時表示,所有的青少年都能安全的使用這項藥物治療。
  
  Harper醫師和同事引導了二項試驗以研究緊急避孕levonorgestrel的安全性和藥物動力學,Harper醫師表示,在1999年這項藥物發行之前,是由WHO所引導,最初試驗於年齡大於18歲的女性中的研究。
  
  她表示,我們沒有任何關於年輕使用者的數據,很顯然地,由於非預期性的懷孕比例高,許多青少年很可能會使用這項藥物。
  
  Harper醫師指出,一般而言,食品藥物管理局非常重視取得小兒科的資料,我們認為在研究這種族群的避孕使用也一樣的重要,這項研究包含55位年齡13到16歲,未懷孕的青春期女孩,且經父母允許參與這項研究。
  
  這些女孩依指示口服0 .75mg 的藥片,12小時之後再服用第二顆,研究人員也研究其中22位對象服藥後三天以上的血液樣品,將結果與成人病患作比較,他們分析在0、0.5、1.0、1.25、1.5、1.75、2、4、8、12、24和72小時的血漿樣品。
  
  Harper醫師表示,98%的青少年女孩適當地使用這項藥品並回復與成人女性相同時間範圍的月經期,青少年的不良反應,如噁心、暈眩、疲勞及頭痛比起WHO研究所觀察到的多,而與西半球的成人族群相比時則沒有這項差異,沒有顯示任何嚴重的不良反應。
  
  Pharmacokinetics研究發現,青少年的系統有比成人婦女更快清除藥物的趨勢,Harper醫師表示,成人有較高的暴露量,而青少年能快速清除它,她把這項差異歸因於拉丁美洲裔的青少年子群具有較高的總血漿清除功能。
  
  Harper醫師表示,這可能是由於蛋白質鍵結的減少,或是人體利用率的減少,在控制了種族及體重後,青少年女性和成人女性則沒有顯著的差異。
  
  在給予不同濃度的藥劑上,這項差異似乎不影響功效,Harper醫師表示,它不大可能具有臨床意義,因為緊急避孕所規定的levonorgestrel劑量是非常高的。
  
  美國北卡羅來納州Chapel Hill生殖研究及評估小組基層的Ipas調查的Ellen Mitchel博士在海報發表中提到,我認為能了解青少年可以使用緊急避孕且沒有不良反應是令人安心的,他們一直被假定有更多的副作用。

Emergency Contraception Safe f

By
Medscape Medical News

Melissa Schorr

Nov. 18, 2003 (San Francisco) — Emergency contraception was safe and well tolerated by teenage girls, a population in which the drug has not previously been tested, researchers reported here Monday at the annual meeting of the American Public Health Association.

"All adolescents took the medications safely," study author Cynthia Harper, PhD, an assistant professor of obstetrics and gynecology at the University of California at San Francisco, told Medscape in an interview.

Dr. Harper and colleagues conducted two tests to study the safety and pharmacokinetics of the emergency contraceptive levonorgestrel, marketed as Plan B.

Before its release in 1999, the drug was tested primarily in women older than 18 years in studies conducted by the World Health Organization (WHO), Dr. Harper noted.

"We didn't have any data in young users," she said. "Obviously, a lot of teenagers could be using this because of the high unintended pregnancy rate."

In general, "the [Food and Drug Administration] has put a lot of emphasis on getting pediatric data," Dr. Harper pointed out. "We think it's just as important to study the use of contraception" in this population.

The study was conducted on 55 teenage girls aged 13 to 16 years who were not pregnant and whose parents gave permission for them to participate.

The girls were administered 0.75 mg of the drug orally, and instructed to take the second tablet 12 hours later. The researchers also studied blood samples from 22 of the girls up to three days after taking the pill, comparing the results with adult patients. They assayed plasma samples at 0, 0.5, 1.0, 1.25, 1.5, 1.75, 2, 4, 8, 12, 24, and 72 hours.

Dr. Harper reported that 98% of the teenage girls used the drug properly and returned to their menstrual period in the same timeframe as the adult women did.

While the teens reported more adverse effects such as nausea, dizziness, fatigue, and headaches than seen in the WHO study, that difference disappeared when they were compared with the adult population from the Western Hemisphere. No serious adverse events were reported.

The pharmacokinetics study found that the teens tended to clear the drug from their system faster than adult women did. "The adults had a higher exposure, the adolescents cleared it faster," Dr. Harper said. She attributed this difference to a subset of Latina adolescents who had higher total plasma clearance.

This may be due to a decrease in protein binding, or possibly a decrease in bioavailability, Dr. Harper said. When controlling for ethnicity and body weight, the difference between the teen girls and adult women was not significant.

At the levels the drug is administered, this difference did not seem to affect efficacy, Dr. Harper said. "It's unlikely to be clinically significant because emergency contraception is prescribed with such a high amount of levonorgestrel."

"I think this is reassuring to know that adolescents can take emergency contraception and have no adverse effects," noted Ellen Mitchell, PhD, a research associate at Ipas, a reproductive research and evaluation group based in Chapel Hill, North Carolina, who commented on the poster presentation. "There has been an assumption they will have more side effects."

The study was funded with grants from the William and Flora Hewlett Foundation, the Women's Capital Corporation, and the General Clinical Research Center at San Francisco General Hospital in California.

APHA 131st Annual Meeting: Poster Session 3070.0, Board 8. Presented Nov. 17, 2003.

Reviewed by Gary D. Vogin, MD

Melissa Schorr is a freelance writer for Medscape.

    
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