This review compares two injectable hormonal contraceptives containing only progestogen, namely depot medroxyprogesterone acetate (DMPA) and norethisterone oenanthate (NET-EN), for the risks and reasons of their discontinuation and for their clinical effe

Injectable hormonal contraceptives remain in extensive use in many developing countries. There are two progestogen-only injectable contraceptives that have been available in many countries since the 1980's. These are depot medroxyprogesterone acetate (DMPA) and norethisterone oenanthate (NET-EN). They are both highly effective contraceptives that receive wide acceptance amongst women in their fertile years, and form a sizeable proportion of the health expenditure on contraception. They differ in frequency of administration and cost, and a systematic comparison aids to ensure their rational use. This review seeks to compare DPMA given at a dose of 150 mg IM every 3 months and NET-EN given at a dose of 200mg IM every 2 months, and determine whether there are differences in contraceptive effectiveness, reversibility and patterns of discontinuation, and their minor and major clinical effects.
All databases were reviewed from the time that injectable progestogens have been in use and this review included all randomised controlled comparisons of DMPA and NET-EN used for contraception. Trials had to report on contraceptive efficiency and return to fertility, the rates and reasons for stopping use, as well as menstrual and non-menstrual clinical effects.
It was found that there was no significant difference between the two treatment groups regarding the time from when women started the contraceptive until they stopped its use. The women on NET-EN were 4% more likely to stop use for personal reasons than those on DPMA, but this difference was not statistically significant. There was no difference between the groups when an accidental pregnancy was the reason to stop use. The length of time of episodes of vaginal bleeding and spotting was the same in each group. Women who were on DPMA were 21% more likely to stop vaginal bleeding altogether while using the contraceptive. Changes in body weight and changes in blood pressure did not differ between DMPA and NET-EN. Furthermore, these changes in body weight and blood pressure were relatively small and not clinically relevant.
In summary, therefore, data from the trials included in this review indicate little difference between the effects of these methods, except that women on DMPA are more likely to experience cessation of vaginal bleeding during its use. There was inadequate data to detect differences in some non-menstrual clinical effects, and considering that this contraceptive method remains in use in some countries, further research is indicated.