LevonorgestrelLevonorgestrel - PDF document

LevonorgestrelLevonorgestrel , 0.75 m g g iven twice 12 hours apart, may be more effective and better tolerated than an estrogen-progestin regimen [18,19 ]. This was illustrated in a controlled trial in which 2000 women with regular menses who requested emergency contraception after unprotected coitus were randomly assigned to either levonorgestrel or the Yuzpe regimen [ ]. The crude pregnancy rates were 1.1 and 3.2 percent, respectively. The proportion of pregnancies prevented (compared with the expected number) was 85 percent with the levonorgestrel regimen and 57 percent with the Yuzpe regimen. Nausea and vomiting were significantly less common with the levonorgestrel. The reduction in side effects and improved efficacy are significant benefits of the progestin-only regimen. In addition, it is an effective alternative for women with a history of thrombosis or who are otherwise unable to take estrogen preparations. levonorgestrel is vomited within one hour of administration, consider g ivin agent and then repeating the emergency contraception dose. The United States FDA has approved marketing of Plan B (by prescription), a pill pack that contains two 0.75 mg tablets of levonorgestrel to be taken twelve hours apart. The cost is comparable to the Preven kit (approximately $20) [ ]. An advisory committee to the FDA recommended Plan B be made available without a prescription, but the FDA rejected this recommendation and requested increased safety information for girls under 16 or restriction of nonprescription availability for girls in this age group [ ]. Other regimens also appeared to be effective in preliminary studies. Further trials confirming efficacy need to be performed before these re g imens can be recommended. They have not beenapproved for emergency contraception by the FDA. Levonorgestrel has been given as a single dose of 1.5 mg instead of two smaller doses. In a randomized trial of 4136 women receiving emergency contraception within 120 hours of intercourse, three regimens were equally effective: a single dose of 1.5 mg of levonorgestrel, two doses of 0.75 mg of levonorgestrel given 12 hours apart, and 10 mg of mifepristone (pregnancy rates of 1.5, 1.8, and 1.5 percent, respectively) [ ]. A single high dose of levonorgestrel was not associated with more side effects. Nausea occurred in 15 percent and vomiting in 1 percent of women; the rates were equivalent for each regimen. The interval between the two doses of levonor g estrel has been len g thened to 24 hours apart,instead of the standard interval of 12 hours apart, without significantly changing efficacy. A multicenter trial in China randomly assigned 2071 women requesting emergency contraception within 120 hours of unprotected intercourse to two doses of 0.75 m g levonor g estrel iven either12 or 24 hours apart [ ]. The crude pregnancy rate was similar in both groups, 2.0 and 1.9 percent, respectively. The proportion of pregnancies prevented was also similar, estimated to be 75 and 72 percent, respectively. Side effects were mild in both groups. The efficacy of the 12-hour regimen declined significantly when there were further acts of intercourse after treatment (failure rate 1 versus 5 percent, respectively); however, this was not observed in the 24 hour group. Mifepristone — The antiprogestin mifepristone (RU-486), 600 mg in one dose, was 100 percent effective at preventing pregnancy in two randomized studies when given within 72 hours after intercourse [23,24 ]. In a subsequent study of 1700 women, a dose of mifepristone as low as 10 mg was as effective as the 600 mg dose and was associated with less disturbance of the subsequent menstrual cycle [ ]. Treatment delay up to 120 hours after unprotected intercourse did not diminish efficacy, although emergency contraception should still be given as early as possible. Overall, data from multiple studies shows that mifepristone (10 mg) is as effective as levonorgestrel (given as a single 1.5 mg dose or two doses of 0.75 mg given 12 hours apart) and is 99 percent effective in preventing pregnancy [21,26 The high efficacy of mifepristone compared with the regimens discussed above is probably due to its

ability to inhibit implantation as well as ovulation [ ]. In most series, it is also associated with a lower incidence of side effects. (See "Progesterone antagonists and progesterone receptor modulators" , and see "Mifepristone for the medical termination of pregnancy" ). á g ina 3de 9 p ToDate®: 'Emer g enc contrace p tion' lication/to ic/marketin p treatment roup, but only 27 percent of the control g roup. Women in the treatment g roup were not more likely to use emergency contraception repeatedly. Unintended pregnancies were less frequent in the treatment group, but this difference did not reach statistical significance (18 versus 25, relative risk 0.7, 95% CI 0.4-1.2). Similar results were obtained in another study of over 2000 women randomly assigned to one of three groups: (1) access to a pharmacy where they could obtain emergency contraception without a prescription, (2) advance provision of emergency contraception, or (3) access to a clinic where they would have to make an appointment to be seen but would be able to receive free emergency contraception [ ]. The major findings from this study were: Only 47 percent of women who had unprotected intercourse during the study used emergency contraception. Women who had advance provision of emergency contraception were more likely to use these drugs than women who had to go to a pharmacy or clinic to obtain them (37, 24, and 21 percent utilization, respectively). However, the advance provision group did not have a significantly lower pregnancy rate compared to the other groups (8 percent versus 7.1 and 8.7 percent in the pharmacy and clinic groups) because of the high rate of unprotected intercourse and relative underutilization of emergency contraception. In this study, as in the one discussed above, easier access to treatment led to higher utilization but did not result in a significant drop in the pregnancy rate of the population. Some limitations of the study may account for these null findings. A significant observation, however, is that the these data do not show any harm from making emergency contraception readily available or any increase in risky sexual behaviors (eg, unprotected intercourse) or acquisition of sexually transmitted disease. Furthermore, g iven the proven efficacy of the method, we can assume thatsome unplanned pregnancies were prevented in women who used emergency contraception, thus benefiting these individuals. Use of UpToDate is subject to the Subscription and License Agreement. Soon, JA, Levine, M, Osmond, BL, et al. Effects of making emergency contraception available without a physician's prescription: a population-based study. CMAJ 2005; 172:878. Grimes, DA. Emergency contraception and fire extinguishers: a prevention paradox. Am J Obstet Gynecol 2002; 187:1536. Grimes, DA. Switching emergency contraception to over-the-counter status. N Engl J Med 2002; 347:846. Raymond, EG, Chen, PL, Dalebout, SM. "Actual use" study of emergency contraceptive pills provided in a simulated over-the-counter manner. Obstet Gynecol 2003; 102:17.5. Steinbrook, R. Waiting for plan B--the FDA and nonprescription use of emergency contraception. N Engl J Med 2004; 350:2327. Harper, CC, Rocca, CH, Darney, PD, et al. Tolerability of levonorgestrel emergency contraception in adolescents. Am J Obstet Gynecol 2004; 191:1158. Raine, T, Harper, C, Leon, K, Darney, P. Emergency contraception: advance provision in a young, high-risk clinic population. Obstet Gynecol 2000; 96:1.8. J Adolesc Health 2003; 32:122. Gold, MA, Wolford, JE, Smith, KA, Parker, AM. The effects of advance provision of ency contraception on adolescent women's sexual and contraceptive behaviors. J Pediatr Adolesc Gynecol 2004; 17:87.10. Glasier, A. Emergency postcoital contraception. N Engl J Med 1997; 337:1058.11. Food and Drug Administration. Prescription drug products: Certain combined oral contraceptives for use as emergency postcoital contraception. Fed Regist 1997; 62:8610.12. ACOG practice bulletin. Emergency oral contraception. Number 25, March 2001. (Replace P á g ina 5de 9 p ToDate®: 'Emer g enc contrace p tion' lication/to ic/marketin p á g ina 7de 9 p ToD

ate®: 'Emer g enc contrace p tion' lication/to ic/marketin p LevonorgestrelLevonorgestrel , 0.75 m g g iven twice 12 hours apart, may be more effective and better tolerated than an estrogen-progestin regimen [18,19 ]. This was illustrated in a controlled trial in which 2000 women with regular menses who requested emergency contraception after unprotected coitus were randomly assigned to either levonorgestrel or the Yuzpe regimen [ ]. The crude pregnancy rates were 1.1 and 3.2 percent, respectively. The proportion of pregnancies prevented (compared with the expected number) was 85 percent with the levonorgestrel regimen and 57 percent with the Yuzpe regimen. Nausea and vomiting were significantly less common with the levonorgestrel. The reduction in side effects and improved efficacy are significant benefits of the progestin-only regimen. In addition, it is an effective alternative for women with a history of thrombosis or who are otherwise unable to take estrogen preparations. levonorgestrel is vomited within one hour of administration, consider g ivin g agent and then repeating the emergency contraception dose. The United States FDA has approved marketing of Plan B (by prescription), a pill pack that contains two 0.75 mg tablets of levonorgestrel to be taken twelve hours apart. The cost is comparable to the Preven kit (approximately $20) [ ]. An advisory committee to the FDA recommended Plan B be made available without a prescription, but the FDA rejected this recommendation and requested increased safety information for girls under 16 or restriction of nonprescription availability for girls in this age group [ ]. Other regimens also appeared to be effective in preliminary studies. Further trials confirming efficacy need to be performed before these re g imens can be recommended. They have not beenapproved for emergency contraception by the FDA. Levonorgestrel has been given as a single dose of 1.5 mg instead of two smaller doses. In a randomized trial of 4136 women receiving emergency contraception within 120 hours of intercourse, three regimens were equally effective: a single dose of 1.5 mg of levonorgestrel, two doses of 0.75 mg of levonorgestrel given 12 hours apart, and 10 mg of mifepristone (pregnancy rates of 1.5, 1.8, and 1.5 percent, respectively) [ ]. A single high dose of levonorgestrel was not associated with more side effects. Nausea occurred in 15 percent and vomiting in 1 percent of women; the rates were equivalent for each regimen. The interval between the two doses of levonor g estrel has been len g thened to 24 hours apart,instead of the standard interval of 12 hours apart, without significantly changing efficacy. A multicenter trial in China randomly assigned 2071 women requesting emergency contraception within 120 hours of unprotected intercourse to two doses of 0.75 m g levonor g estrel g iven either12 or 24 hours apart [ ]. The crude pregnancy rate was similar in both groups, 2.0 and 1.9 percent, respectively. The proportion of pregnancies prevented was also similar, estimated to be 75 and 72 percent, respectively. Side effects were mild in both groups. The efficacy of the 12-hour regimen declined significantly when there were further acts of intercourse after treatment (failure rate 1 versus 5 percent, respectively); however, this was not observed in the 24 hour group. Mifepristone — The antiprogestin mifepristone (RU-486), 600 mg in one dose, was 100 percent effective at preventing pregnancy in two randomized studies when given within 72 hours after intercourse [23,24 ]. In a subsequent study of 1700 women, a dose of mifepristone as low as 10 mg was as effective as the 600 mg dose and was associated with less disturbance of the subsequent menstrual cycle [ ]. Treatment delay up to 120 hours after unprotected intercourse did not diminish efficacy, although emergency contraception should still be given as early as possible. Overall, data from multiple studies shows that mifepristone (10 mg) is as effective as levonorgestrel (given as a single 1.5 mg dose or two doses of 0.75 mg given 12 hours apart) and is 99 percent effective in preventing pregnancy [21,26 The high efficacy of mifeprist

one compared with the regimens discussed above is probably due to its ability to inhibit implantation as well as ovulation [ ]. In most series, it is also associated with a lower incidence of side effects. (See "Progesterone antagonists and progesterone receptor modulators" , and see "Mifepristone for the medical termination of pregnancy" ). P á g ina 3de 9 p ToDate®: 'Emer g enc y contrace p tion' 10/08/2005 LevonorgestrelLevonorgestrel , 0.75 m g g iven twice 12 hours apart, may be more effective and better tolerated than an estrogen-progestin regimen [18,19 ]. This was illustrated in a controlled trial in which 2000 women with regular menses who requested emergency contraception after unprotected coitus were randomly assigned to either levonorgestrel or the Yuzpe regimen [ ]. The crude pregnancy rates were 1.1 and 3.2 percent, respectively. The proportion of pregnancies prevented (compared with the expected number) was 85 percent with the levonorgestrel regimen and 57 percent with the Yuzpe regimen. Nausea and vomiting were significantly less common with the levonorgestrel. The reduction in side effects and improved efficacy are significant benefits of the progestin-only regimen. In addition, it is an effective alternative for women with a history of thrombosis or who are otherwise unable to take estrogen preparations. levonorgestrel is vomited within one hour of administration, consider g ivin g agent and then repeating the emergency contraception dose. The United States FDA has approved marketing of Plan B (by prescription), a pill pack that contains two 0.75 mg tablets of levonorgestrel to be taken twelve hours apart. The cost is comparable to the Preven kit (approximately $20) [ ]. An advisory committee to the FDA recommended Plan B be made available without a prescription, but the FDA rejected this recommendation and requested increased safety information for girls under 16 or restriction of nonprescription availability for girls in this age group [ ]. Other regimens also appeared to be effective in preliminary studies. Further trials confirming efficacy need to be performed before these re g imens can be recommended. They have not beenapproved for emergency contraception by the FDA. Levonorgestrel has been given as a single dose of 1.5 mg instead of two smaller doses. In a randomized trial of 4136 women receiving emergency contraception within 120 hours of intercourse, three regimens were equally effective: a single dose of 1.5 mg of levonorgestrel, two doses of 0.75 mg of levonorgestrel given 12 hours apart, and 10 mg of mifepristone (pregnancy rates of 1.5, 1.8, and 1.5 percent, respectively) [ ]. A single high dose of levonorgestrel was not associated with more side effects. Nausea occurred in 15 percent and vomiting in 1 percent of women; the rates were equivalent for each regimen. The interval between the two doses of levonor g estrel has been len g thened to 24 hours apart,instead of the standard interval of 12 hours apart, without significantly changing efficacy. A multicenter trial in China randomly assigned 2071 women requesting emergency contraception within 120 hours of unprotected intercourse to two doses of 0.75 m g levonor g estrel g iven either12 or 24 hours apart [ ]. The crude pregnancy rate was similar in both groups, 2.0 and 1.9 percent, respectively. The proportion of pregnancies prevented was also similar, estimated to be 75 and 72 percent, respectively. Side effects were mild in both groups. The efficacy of the 12-hour regimen declined significantly when there were further acts of intercourse after treatment (failure rate 1 versus 5 percent, respectively); however, this was not observed in the 24 hour group. Mifepristone — The antiprogestin mifepristone (RU-486), 600 mg in one dose, was 100 percent effective at preventing pregnancy in two randomized studies when given within 72 hours after intercourse [23,24 ]. In a subsequent study of 1700 women, a dose of mifepristone as low as 10 mg was as effective as the 600 mg dose and was associated with less disturbance of the subsequent menstrual cycle [ ]. Treatment delay up to 120 hours after unprotected intercourse did not dimini

sh efficacy, although emergency contraception should still be given as early as possible. Overall, data from multiple studies shows that mifepristone (10 mg) is as effective as levonorgestrel (given as a single 1.5 mg dose or two doses of 0.75 mg given 12 hours apart) and is 99 percent effective in preventing pregnancy [21,26 The high efficacy of mifepristone compared with the regimens discussed above is probably due to its ability to inhibit implantation as well as ovulation [ ]. In most series, it is also associated with a lower incidence of side effects. (See "Progesterone antagonists and progesterone receptor modulators" , and see "Mifepristone for the medical termination of pregnancy" ). P á g ina 3de 9 p ToDate®: 'Emer g enc y contrace p tion' Because mifepristone delays but does not prevent ovulation, contraception should be used if there are further coital episodes during the cycle as with hormonal emergency contraception. — A copper intrauterine device placed within 120 hours of unprotected intercourse can also be used as a form of emergency contraception [ ]. An advantage of this method is that it provides continuing contraception after the initial event. See "The intrauterine contraceptive device" ). ADMINISTRATION OF EMERGENCY CONTRACEPTION — When prescribing emergency contraception, the physician should inquire whether the act of intercourse for which the contraception is being requested was consensual. If not, the physical and psychological assessment for rape victims should be initiated. (See "Evaluation and management of rape victims" ). Recommended regimenLevonorgestrel is preferred over estrogen-progestin regimens because of higher efficacy and fewer side effects. If an estrogen-progestin regimen is prescribed, an antiemetic drug should be taken one hour before the first dose. Timing — Both the levonorgestrel and Yuzpe regimens are most effective when given soon after unprotected intercourse. There appears to be a linear relationship between efficacy and the time from intercourse to treatment; in one study, pregnancy rates increased from 0.5 percent (2 of 386) to 4 percent (6 of 146) when treatment was administered within 12 hours and 61 to 72 hours after intercourse, respectively [19,28 ]. Therefore, it is preferable to administer these regimens as soon as possible after intercourse. However, subsequent studies have shown that emergency oral contraception has efficacy up to 120 hours after intercourse and may be started up to that time if necessary [21,29,30 ], although patients should be informed that efficacy may be reduced. Efficacy after 120 hours has not been proven. Insertion of a copper intrauterine device is considered the best way to prevent pregnancy in women who seek emergency contraception more than 120 hours after unprotected intercourse [ ]. — Nausea and vomiting are the most common side effects. Antiemetics can be given, prophylactically with the Yuzpe regimen (see "Ethinyl estradiol plus levonorgestrel" above ) or as needed (see "Levonorgestrel" above ). Uncommon side effects include irregular bleeding, dizziness, fatigue, headache, breast tenderness, and lower abdominal pain. These may be treated symptomatically. Additional contraception — Women using emergency contraception pills should be advised that a risk of pregnancy still exists if they have intercourse after emergency contraception pills have been taken. Therefore, they should use a method of contraception for the rest of the cycle. They may start barrier or hormonal methods the day after the last EC pill. The duration of effectiveness of emergency contraception has not been determined. There is no contraindication to giving a second dose of emergency contraception if a second episode of unprotected intercourse occurs anytime after the first dose was administered [ Follow-up — Menstrual bleeding after emergency contraception typically occurs within one week of the expected time. Exceptions are with the intrauterine device and mifepristone ; in one report, 42 percent of women receiving this drug had a delay in onset of the next menstrual period compared to 13 percent of those receiving ethinyl es

tradiol and norgestrel [23 Nevertheless, with any form of emer g ency contraception, a pre g nancy test should be performedif bleeding has not occurred within three to four weeks [12,14 ]. — Giving women a home supply of emergency contraceptives (or an advance prescription for emergency contraception) in addition to their primary mode of contraception may reduce the number of unwanted pregnancies. This was illustrated in a study of over 1000 women that co g iven a supply of emer g ency contraceptive pills to take home (treatment g roup) with those who could only g et them by visitin g a physician (control group) [ ]. Emergency contraception was used at least once by 47 percent of the P á g ina 4de 9 p ToDate®: 'Emer g enc y contrace p tion' 10/08/2005 Because mifepristone delays but does not prevent ovulation, contraception should be used if there are further coital episodes during the cycle as with hormonal emergency contraception. — A copper intrauterine device placed within 120 hours of unprotected intercourse can also be used as a form of emergency contraception [ ]. An advantage of this method is that it provides continuing contraception after the initial event. See "The intrauterine contraceptive device" ). ADMINISTRATION OF EMERGENCY CONTRACEPTION — When prescribing emergency contraception, the physician should inquire whether the act of intercourse for which the contraception is being requested was consensual. If not, the physical and psychological assessment for rape victims should be initiated. (See "Evaluation and management of rape victims" ). Recommended regimenLevonorgestrel is preferred over estrogen-progestin regimens because of higher efficacy and fewer side effects. If an estrogen-progestin regimen is prescribed, an antiemetic drug should be taken one hour before the first dose. Timing — Both the levonorgestrel and Yuzpe regimens are most effective when given soon after unprotected intercourse. There appears to be a linear relationship between efficacy and the time from intercourse to treatment; in one study, pregnancy rates increased from 0.5 percent (2 of 386) to 4 percent (6 of 146) when treatment was administered within 12 hours and 61 to 72 hours after intercourse, respectively [19,28 ]. Therefore, it is preferable to administer these regimens as soon as possible after intercourse. However, subsequent studies have shown that emergency oral contraception has efficacy up to 120 hours after intercourse and may be started up to that time if necessary [21,29,30 ], although patients should be informed that efficacy may be reduced. Efficacy after 120 hours has not been proven. Insertion of a copper intrauterine device is considered the best way to prevent pregnancy in women who seek emergency contraception more than 120 hours after unprotected intercourse [ ]. — Nausea and vomiting are the most common side effects. Antiemetics can be given, prophylactically with the Yuzpe regimen (see "Ethinyl estradiol plus levonorgestrel" above ) or as needed (see "Levonorgestrel" above ). Uncommon side effects include irregular bleeding, dizziness, fatigue, headache, breast tenderness, and lower abdominal pain. These may be treated symptomatically. Additional contraception — Women using emergency contraception pills should be advised that a risk of pregnancy still exists if they have intercourse after emergency contraception pills have been taken. Therefore, they should use a method of contraception for the rest of the cycle. They may start barrier or hormonal methods the day after the last EC pill. The duration of effectiveness of emergency contraception has not been determined. There is no contraindication to giving a second dose of emergency contraception if a second episode of unprotected intercourse occurs anytime after the first dose was administered [ Follow-up — Menstrual bleeding after emergency contraception typically occurs within one week of the expected time. Exceptions are with the intrauterine device and mifepristone ; in one report, 42 percent of women receiving this drug had a delay in onset of the next menstrual period compared to 13 percent of those receiving eth

inyl estradiol and norgestrel [23 Nevertheless, with any form of emer g ency contraception, a pre g nancy test should be performedif bleeding has not occurred within three to four weeks [12,14 ]. — Giving women a home supply of emergency contraceptives (or an advance prescription for emergency contraception) in addition to their primary mode of contraception may reduce the number of unwanted pregnancies. This was illustrated in a study of over 1000 women that co g iven a supply of emer g ency contraceptive pills to take home (treatment g roup) with those who could only g et them by visitin g a physician (control group) [ ]. Emergency contraception was used at least once by 47 percent of the P á g ina 4de 9 p ToDate®: 'Emer g enc y contrace p tion' treatment g roup, but only 27 percent of the control g roup. Women in the treatment g roup were not more likely to use emergency contraception repeatedly. Unintended pregnancies were less frequent in the treatment group, but this difference did not reach statistical significance (18 versus 25, relative risk 0.7, 95% CI 0.4-1.2). Similar results were obtained in another study of over 2000 women randomly assigned to one of three groups: (1) access to a pharmacy where they could obtain emergency contraception without a prescription, (2) advance provision of emergency contraception, or (3) access to a clinic where they would have to make an appointment to be seen but would be able to receive free emergency contraception [ ]. The major findings from this study were: Only 47 percent of women who had unprotected intercourse during the study used emergency contraception. Women who had advance provision of emergency contraception were more likely to use these drugs than women who had to go to a pharmacy or clinic to obtain them (37, 24, and 21 percent utilization, respectively). However, the advance provision group did not have a significantly lower pregnancy rate compared to the other groups (8 percent versus 7.1 and 8.7 percent in the pharmacy and clinic groups) because of the high rate of unprotected intercourse and relative underutilization of emergency contraception. In this study, as in the one discussed above, easier access to treatment led to higher utilization but did not result in a significant drop in the pregnancy rate of the population. Some limitations of the study may account for these null findings. A significant observation, however, is that the these data do not show any harm from making emergency contraception readily available or any increase in risky sexual behaviors (eg, unprotected intercourse) or acquisition of sexually transmitted disease. Furthermore, g iven the proven efficacy of the method, we can assume thatsome unplanned pregnancies were prevented in women who used emergency contraception, thus benefiting these individuals. Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Soon, JA, Levine, M, Osmond, BL, et al. Effects of making emergency contraception available without a physician's prescription: a population-based study. CMAJ 2005; 172:878. Grimes, DA. Emergency contraception and fire extinguishers: a prevention paradox. Am J Obstet Gynecol 2002; 187:1536. Grimes, DA. Switching emergency contraception to over-the-counter status. N Engl J Med 2002; 347:846. Raymond, EG, Chen, PL, Dalebout, SM. "Actual use" study of emergency contraceptive pills provided in a simulated over-the-counter manner. Obstet Gynecol 2003; 102:17.5. Steinbrook, R. Waiting for plan B--the FDA and nonprescription use of emergency contraception. N Engl J Med 2004; 350:2327. Harper, CC, Rocca, CH, Darney, PD, et al. Tolerability of levonorgestrel emergency contraception in adolescents. Am J Obstet Gynecol 2004; 191:1158. Raine, T, Harper, C, Leon, K, Darney, P. Emergency contraception: advance provision in a young, high-risk clinic population. Obstet Gynecol 2000; 96:1.8. J Adolesc Health 2003; 32:122. Gold, MA, Wolford, JE, Smith, KA, Parker, AM. The effects of advance provision of g ency contraception on adolescent women's sexual and contraceptive behaviors. J Pediatr Adolesc Gynecol 2004; 17:87.10. Glasier, A. Emerge

ncy postcoital contraception. N Engl J Med 1997; 337:1058.11. Food and Drug Administration. Prescription drug products: Certain combined oral contraceptives for use as emergency postcoital contraception. Fed Regist 1997; 62:8610.12. ACOG practice bulletin. Emergency oral contraception. Number 25, March 2001. (Replace P á g ina 5de 9 p ToDate®: 'Emer g enc y contrace p tion' 10/08/2005 treatment g roup, but only 27 percent of the control g roup. Women in the treatment g roup were not more likely to use emergency contraception repeatedly. Unintended pregnancies were less frequent in the treatment group, but this difference did not reach statistical significance (18 versus 25, relative risk 0.7, 95% CI 0.4-1.2). Similar results were obtained in another study of over 2000 women randomly assigned to one of three groups: (1) access to a pharmacy where they could obtain emergency contraception without a prescription, (2) advance provision of emergency contraception, or (3) access to a clinic where they would have to make an appointment to be seen but would be able to receive free emergency contraception [ ]. The major findings from this study were: Only 47 percent of women who had unprotected intercourse during the study used emergency contraception. Women who had advance provision of emergency contraception were more likely to use these drugs than women who had to go to a pharmacy or clinic to obtain them (37, 24, and 21 percent utilization, respectively). However, the advance provision group did not have a significantly lower pregnancy rate compared to the other groups (8 percent versus 7.1 and 8.7 percent in the pharmacy and clinic groups) because of the high rate of unprotected intercourse and relative underutilization of emergency contraception. In this study, as in the one discussed above, easier access to treatment led to higher utilization but did not result in a significant drop in the pregnancy rate of the population. Some limitations of the study may account for these null findings. A significant observation, however, is that the these data do not show any harm from making emergency contraception readily available or any increase in risky sexual behaviors (eg, unprotected intercourse) or acquisition of sexually transmitted disease. Furthermore, g iven the proven efficacy of the method, we can assume thatsome unplanned pregnancies were prevented in women who used emergency contraception, thus benefiting these individuals. Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Soon, JA, Levine, M, Osmond, BL, et al. Effects of making emergency contraception available without a physician's prescription: a population-based study. CMAJ 2005; 172:878. Grimes, DA. Emergency contraception and fire extinguishers: a prevention paradox. Am J Obstet Gynecol 2002; 187:1536. Grimes, DA. Switching emergency contraception to over-the-counter status. N Engl J Med 2002; 347:846. Raymond, EG, Chen, PL, Dalebout, SM. "Actual use" study of emergency contraceptive pills provided in a simulated over-the-counter manner. Obstet Gynecol 2003; 102:17.5. Steinbrook, R. Waiting for plan B--the FDA and nonprescription use of emergency contraception. N Engl J Med 2004; 350:2327. Harper, CC, Rocca, CH, Darney, PD, et al. Tolerability of levonorgestrel emergency contraception in adolescents. Am J Obstet Gynecol 2004; 191:1158. Raine, T, Harper, C, Leon, K, Darney, P. Emergency contraception: advance provision in a young, high-risk clinic population. Obstet Gynecol 2000; 96:1.8. J Adolesc Health 2003; 32:122. Gold, MA, Wolford, JE, Smith, KA, Parker, AM. The effects of advance provision of g ency contraception on adolescent women's sexual and contraceptive behaviors. J Pediatr Adolesc Gynecol 2004; 17:87.10. Glasier, A. Emergency postcoital contraception. N Engl J Med 1997; 337:1058.11. Food and Drug Administration. Prescription drug products: Certain combined oral contraceptives for use as emergency postcoital contraception. Fed Regist 1997; 62:8610.12. ACOG practice bulletin. Emergency oral contraception. Number 25, March 2001. (Replace P á g ina 5de 9 p ToDate®: 'Emer g enc y contrace p