You have to taper off any psych drugs very carefully. You may be tapering too fast, and having a withdrawal syndrome causing the headaches and insomnia.
http://en.wikipedia.org/wiki/Mirtazapine
Discontinuation
Mirtazapine and other
antidepressants may cause a
withdrawal syndrome upon
discontinuation.
[2][50][51][52] A gradual and slow reduction in dose is recommended in order to minimize withdrawal symptoms.
[53] Effects of sudden cessation of treatment with mirtazapine may include depression,
anxiety,
panic attacks,
vertigo,
restlessness,
irritability,
decreased appetite,
insomnia,
diarrhea,
nausea,
vomiting,
flu-like symptoms such as
allergies and
pruritus,
headaches, and sometimes
hypomania or
mania.
[50][
I'm currently tapering from another psych drug, Zoloft. The recommended taper for anti-depressants is to reduce only 10% of the previous dose every 3-6 weeks. This gives your brain a chance to adjust to the change in medication. If you get any withdrawal symptoms, they'll be mild and manageable. I'm actually reducing every 8 weeks. The last week or two, I don't have any withdrawal symptoms. This gives me a nice little break until I'm ready to reduce again.
So if you wanted to reduce the M, your first reduction would be 6.75mg, and hold that for 3-6 weeks. If you're going any faster than that, the withdrawal may be more than you can tolerate.
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I haven't heard of any medication that we normally take that would interfere with methylation. (The only exception I can think of is Methotrexate, which reduces folate. This is used for cancer.)
There may be a "honeymoon period" of six weeks or so before you notice anything on the methylation protocol.
You may want to have some niacin on hand in case methylation kicks in suddenly. I hope you aren't taking full doses. Watch my video series "Methylation Made Easy" (the link is in my signature below).
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I use self muscle testing to determine not only what I can tolerate, but also dose amounts. You have to be careful not to crank up methylation too much while you're on a psych drug. Via muscle testing, your body can tell you what amount is safe to take while on the drug, when to increase as you decrease the drug, and so on.
There are many videos on Youtube to learn this. To determine amounts, just ask a series of yes or no questions regarding amounts, until you hit on one that tests strong.