So my thyroid is finally in remission. It took 7 months of being on methimazole was nasty side?

Methimazole is rapidly metabolized and has a half life of 6 to 13 hours.
This means that every 6 to 13 hours, half of the previous amount of methimazole in your body disappears.

How long it takes your body to get rid of methimazole is very hard to determine and also depends on :
1. How much and how often you have taken the drug.
2. Your metabolic rate – a slower metabolism will increase the time a drug remains in your system.
3. Your age and health – older age and poor health will generally increase the time the drug stays in your system.
4. Body mass – generally the bigger you are the longer a drug will remain in your system.

You should talk to your doctor if there is any specific side-effect you are concerned about.