Long-term effects of Prozac

I've been taking 40 mgs Prozac for nearly 6 months and recently upped my dosage to 60 mgs/day.  I've noticed somewhat of a change in my submission to depression but still am not sure why I feel irritable, angry and flighty during other weeks.

The first time I was subscribed the anti-depressant I was fine, beautiful, life couldn't have been more problem free, but I'm confused as to why the effects aren't as strong this time.  

I was wondering if my hypothryoidism is the cause of the minimal Prozac effects, if my depression has evolved into a different type of diseaseor if Prozac just automatically is weakened by the immune system after the initial round?

[HFHS MD -RG]

Depression is often multifactorial, meaning it may be caused by different factors including personal and family history of depression, environmental stressors, and medical factors. Your response to Prozac in the past may be influenced by the prevailing environmental influences at that time. The product information of Prozac reveals that infrequently Prozac may cause or worsen  preexisting hypothyroidism. As hypothyroidism is known to cause depression, it is important to have your thyroid function checked. There are case reports of individuals responding to a medication, such as Prozac, at one time and then being refractory to it the next.  It is unclear why this happens.  It may be worthwhile trying a different antidepressant.

The symptoms that you experience after increasing the dosage of Prozac are a frequent side effect of this medication. The agitation and emotional lability should improve in a week or so. Often times, to lessen the experience of this side effect a slow increase of the medication is done i.e. increase by 10mg instead of 20mg.

I suggest a consult with your physician to monitor your current thyroid hormone levels and to discuss your current symptomatology.

I wish you the best,

HFHS MD - RG

*Keyword: Prozac