I've been taking Venlafaxine (Effexor XR) and Mirtazapine for 18 months. As I understand it (and by my own experience) Mirtazapine has more soporific effects at the lower end of the dosage spectrum -
maybe 15mg plus. It took me a couple of weeks for the sluggish feeling the next day to go away. I know what you mean about "couldn't keep my eyes open" - I kind of like that effect because I've always had trouble sleeping. In fact, when that effect diminished every few months, I increased the Mirtazapine. I'm now on 180mg which I take at 8pm sharp! All that aside, Mirtazapine is also often reported to be effective in the shortest amount of time - maybe a few weeks.
I have put on 20kg in the past 18 months & I blame the Mirtazapine for that. I suppose it's really just my hand & mouth doing all the real work. I was never really an "active" person, so this just helped me pile on the weight a lot.
I started on 75mg of Effexor XR (Venlafaxine in sustained release) but it didn't really start helping me till I got to 150mg. Then after 4 months or so it would "poop out" and I'd increase the dose. I'm now on 600mg / day and that's really working for me. It doesn't seem to matter to me if I take this in the morning or at night - that's the idea of the sustained release version (XR).
Even at these unusually high doses, I'm not getting any odd side-effects. I mean that the side effects I have always had have not increased with dosage. I get somnolence (which I need) plus eating more (which is bad) with the Mirtazapine. I get anxiety (for 2 weeks when the dosage is bumped up) and no libido (who cares?) and more energy during the day (which is good) and probably high blood pressure (bad of course but maybe weight related anyway).
I urged my Dr to put me on the Mirtazapine as well as the Venlafaxine early on. This combination is commonly known as "California rocket fuel". The idea is that selectively affecting several depression-related receptors is better than only affecting say, one.
If you can get a hold of a PDF book called "Stephen M. Stahl - Essential Psychopharmacology.pdf" it has lots of pretty pictures & is not too hard to follow. It has a lot of examples about how each anti-depressant works & therefore why some combinations are better than others. It's "available" on peer-to-peer and torrent sharing sites.
Here's a quote:
“ **"California rocket fuel": High-dose Venlafaxine plus Mirtazapine. This is a combination of antidepressants that has a great degree of theoretical synergy: reuptake blockade plus alpha 2 blockade; serotonin reuptake plus 5HT2A antagonism; 5HT actions plus NE actions. Specifically, 5HT is triple-boosted, with reuptake blockade, alpha 2 antagonism, and 5HT2A antagonism; NE is double-boosted, with reuptake blockade plus alpha 2 antagonism; and there may even be a bit of single boost to DA from reuptake blockade."} “
(much better with the pictures