Mirena Poster

Dr Diana Mansour answers your questions

  • Is Mirena well tolerated?
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Tolerability and Mirena

Tolerability can be thought of in terms of how likely it is for a woman to continue using Mirena and how frequently Mirena is removed because of adverse events and complications1.

Table 7 shows the Mirena discontinuation rates in two separate 5-year studies where Mirena was compared with a Cu-UD. Reasons for discontinuation included: pregnancy, expulsion, amenorrhea, bleeding problems, other menstrual/pain problems, pain, pelvic inflammatory disease, other medical issues, planning pregnancy, other personal reasons2,3,4.

Table 7: Comparison of discontinuation rates with Mirena and Cu-IUDs in two separate 5-year studies. Study A:2,3 Study B:4

Event Study 1 year 5 years
Cu-IUD Mirena Cu-IUD Mirena
Pregnancy A
B		 1.0
0.3		 0.1
0.2		 5.9
1.4		 0.5***
1.1
Expulsion A
B		 3.9
5.6		 3.7
6.3		 6.7
7.4		 5.8
11.8*
Amenorrhea A
B		 0.0
0.2		 1.6
4.5		 0.0
0.4		 6.0***
19.7***
Bleeding problems A 6.3 6.2 20.9 13.7*
Other menstrual/pain B 6.7 6.1 23.3 15.4**
Pain A 1.7 1.8 5.8 5.9
Hormonal A 0.1 2.7 2.0 12.1***
PID A
B		 NR
NR		 NR
NR		 2.2
2.3		 0.8*
2.6
Other Medical A
B		 3.1
3.9		 3.3
4.5		 10.6
16.2		 7.7*
16.9
Planning pregnacy A
B		 2.3
1.6		 2.3
2.6		 16.3
23.5		 15.2
25.9
Other personal A
B		 0.7
1.3		 0.6
2.2		 5.9
9.4		 4.4
9.5
Continuation A
B		 NR
81.8		 NR
76.3		 53.1
40.6		 55.5
33.0***
*p<0.05; **p<0.01; ***p<0.001.
NR = not reported; PID = pelvic inflammatory disease.

Two 5-year studies showed that continuation rates were higher with Mirena (53% and 47%, Luukainen et al.5 and Andersson et al.2 respectively compared with a Cu-IUD (Nova T, 50% and 45%).The continuation rate was higher in the older age group for both contraceptive methods2. In contrast, when compared with another Cu-IUD (Cu T380 Ag) over 5 years of use, Mirena had a lower continuation rate (33.0% vs. 40.6%)6, the main contributor to the difference being terminations related to amenorrhea in the Mirena group4.

However, the value of counselling can be seen in the discontinuation rates among women who received appropriate counselling. A post-marketing study by Backman et al.7,8 involving over 17,000 Mirena users, in which continuation rates were 93% at 1 year and 65% at 5 years, showed that the continuation rates are high in routine clinical practice in appropriately counselled women (Figure 16).

Continuation rates with Mirena in routine clinical practice in different user age groups.Figure 16: Continuation rates with Mirena in routine clinical practice in different user age groups7.

A multivariate analysis from this study8 showed that excessive bleeding and spotting carried the highest relative risk ratio for discontinuation (2.77), whereas occasional or total absence of menstruation carried the lowest (0.46). Once women were reassured that infrequent or absent bleeding is benign, they regarded it as an advantage. Hence, amenorrhea-related discontinuation rates are lower in studies that incorporate counselling.

It has also been shown that in women aged 35 - 45 who switched to Mirena due to dissatisfaction with their previous contraceptive, the continuation rate after 12 months’ treatment was about 90%9. The continuation rates with Mirena are similar in women who switch from Cu-IUDs and in women who switch from oral contraceptives9.