Place in therapy
Efficacy
The efficacy of levonorgestrel as emergency contraception is well established. Several trials have demonstrated its’ efficacy to be equal or superior to other forms of emergency contraception offered worldwide1,3,4. In addition, non-inferiority in efficacy was found when a levonorgestrel two-dose regimen (Two 0.75 mg tablets taken 12 h apart) was compared to the single-dose levonorgestrel regimen (1.5 mg taken upon request of emergency contraception). Post treatment pregnancy percentages were not significantly different1. Lastly, timing of treatment is essential in the success of prevention of unplanned pregnancies. Studies have found that participants treated after 72 h of unprotected intercourse demonstrated more pregnancies than those treated within 72 hours1,2. It should be cautioned that levonorgestrel emergency contraception is not an abortifacient and does not offer protection against sexually transmitted diseases5.
Safety
Levonorgestrel is well tolerated and studies to date support less frequent adverse events with the use of levonorgestrel as emergency contraception compared to other treatment regimens1,2,3,4,5. Most common side effects include nausea, abdominal pain, fatigue, headache, dizziness and breast tenderness5. Women who are pregnant or who suspect they are pregnant should not be administered this drug. In addition, patients with undiagnosed abnormal vaginal bleeding should also be advised to avoid levonorgestrel as emergency contraception5. Regular use of this product (greater than once a month) may cause significant changes in the menstrual cycle and repeated use therefore, is cautioned against5.
References
1. Dada OA, Godfrey EM, Piaggio G and von Hertzen H. 2010. A randomized, double-
blind, non-inferiority study to compare two regimens of levonorgestrel for emergency contraception in Nigeria. Contraception: 82: 373-378.
2. Noe G, Croxatto HB, Salvatierra AM et al. 2011. Contraceptive efficacy of emergency
contraception with levonorgestrel given before and after ovulation. Contraception. 84: 486-492.
3. Grimes D, von Hertzen H, Piaggio G and Van Look PFA. 1998. Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception. The Lancet. 352:428-433.
4. von Hertzen H, Piaggio G, Ding J et al. 2002. Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: a WHO multicentre randomized trial. The Lancet. 360: 1803-1810.
5. Levonorgestrel [product monograph]. e-therapeutics. Last Updated: June 10, 2010. Accessed at: https://www-etherapeuticsca.proxy.lib.uwaterloo.ca/cps. select.preliminaryFilter. action?simplePreliminaryFilter =levonorgestrel# on June 27, 2012.
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Efficacy
The efficacy of levonorgestrel as emergency contraception is well established. Several trials have demonstrated its’ efficacy to be equal or superior to other forms of emergency contraception offered worldwide1,3,4. In addition, non-inferiority in efficacy was found when a levonorgestrel two-dose regimen (Two 0.75 mg tablets taken 12 h apart) was compared to the single-dose levonorgestrel regimen (1.5 mg taken upon request of emergency contraception). Post treatment pregnancy percentages were not significantly different1. Lastly, timing of treatment is essential in the success of prevention of unplanned pregnancies. Studies have found that participants treated after 72 h of unprotected intercourse demonstrated more pregnancies than those treated within 72 hours1,2. It should be cautioned that levonorgestrel emergency contraception is not an abortifacient and does not offer protection against sexually transmitted diseases5.
Safety
Levonorgestrel is well tolerated and studies to date support less frequent adverse events with the use of levonorgestrel as emergency contraception compared to other treatment regimens1,2,3,4,5. Most common side effects include nausea, abdominal pain, fatigue, headache, dizziness and breast tenderness5. Women who are pregnant or who suspect they are pregnant should not be administered this drug. In addition, patients with undiagnosed abnormal vaginal bleeding should also be advised to avoid levonorgestrel as emergency contraception5. Regular use of this product (greater than once a month) may cause significant changes in the menstrual cycle and repeated use therefore, is cautioned against5.
References
1. Dada OA, Godfrey EM, Piaggio G and von Hertzen H. 2010. A randomized, double-
blind, non-inferiority study to compare two regimens of levonorgestrel for emergency contraception in Nigeria. Contraception: 82: 373-378.
2. Noe G, Croxatto HB, Salvatierra AM et al. 2011. Contraceptive efficacy of emergency
contraception with levonorgestrel given before and after ovulation. Contraception. 84: 486-492.
3. Grimes D, von Hertzen H, Piaggio G and Van Look PFA. 1998. Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception. The Lancet. 352:428-433.
4. von Hertzen H, Piaggio G, Ding J et al. 2002. Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: a WHO multicentre randomized trial. The Lancet. 360: 1803-1810.
5. Levonorgestrel [product monograph]. e-therapeutics. Last Updated: June 10, 2010. Accessed at: https://www-etherapeuticsca.proxy.lib.uwaterloo.ca/cps. select.preliminaryFilter. action?simplePreliminaryFilter =levonorgestrel# on June 27, 2012.
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