Hi there racjen - I looked up the product info on Mirena, specifically the pharmacokinetics - which is how the product is metabolised in the body over time and it says this:
"The pharmacokinetics of levonorgestrel itself have been extensively investigated and reported in the literature. In postmenopausal users of Mirena who were receiving non-oral concomitant oestrogen, plasma levonorgestrel concentrations have been 276 ±119 pg/ml, 196 ± 87pg/ml and 177 ± 70 pg/ml at 56 weeks, 24 months and 48 months respectively. A half life of 20 hours is considered the best estimate although some studies have reported values as short as 9 hours and others as long as 80 hours. Another important finding, although one in agreement with experience with other synthetic steroids, has been marked differences in metabolic clearance rates among individuals, even when administration was by the intravenous route. Levonorgestrel is extensively bound to proteins (mainly sex hormone binding globulin (SHBG) and extensively metabolised to a large number of inactive metabolites."
From this you will see there is great variation in the half life due to differences in metabolic clearance so hang in there - your feelings are not unusual especially as you are very sensitive to medication as BlueButterfly says.
I hope today has been a better day ...
Hurdity x
