Emergency contraception in women weighing > 70 kg; consider two tablets i.e. 3.0 mg

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Emergency contraception in women weighing > 70 kg; consider two tablets i.e. 3.0 mg

Emergency contraceptive pill(s) needs to be taken within 72 hours of unprotected sexual intercourse (UPSI), with lower efficacy up to 120 hrs after UPSI. 

For women who weigh > 70 kg or over 26kg/m2 and those who have taken enzyme inducing medication drugs in the past 4 weeks then two pills (2 x 1.5 mg tablets) are recommended.

The estimated pregnancy rate at the daily equivalent of 1.5mg increased significantly from 1.4% among the group of women weighing 65–75 kg to 6.4%  and 5.7%  in the 75–85 kg and > 85 kg groups respectively (based on 2 RCTs).2

A barrier method of contraception needs to be used until the next period. A more effective option is to insert a copper IUD (99% effective) which can be inserted up to 5 days post-intercourse and has the advantage of providing longer term contraception. Vomiting within 3 hours also necessitates another treatment.  

This Gem has been checked by Dr Karen Hoare, Nurse Practitioner.

References:

  1. NZ Formulary Click here 
  2. Effect of body weight and BMI on the efficacy of levonorgestrel emergency contraception. Contraception 2015 Click here 

Gems are chosen by the Goodfellow director Dr. Bruce Arroll to be either practice changing or practice maintaining. The information is educational and not clinical advice.

 
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As published in NZ Doctor 13/02/2019