Oh, gosh. It's frustrating, isn't it? My little guy is such a happy, bouncy goofball of a dog until he goes into reactivity mode. It really is so sad that he's so scared, and (probably selfishly) it's sad for me that I can't get out there and share him with the world. If he weren't so reactive, he'd have so many friends. He's just got a great personality otherwise.
For me, putting him on meds is a continuing journey. My old vet wouldn't entertain the idea of anything but Ace (Ace is very, very bad). I asked another vet who said he needed meds but she also wanted to do training with me, which I understand is totally necessary (we also work with a trainer) but her methods made me really uncomfortable. So another dead end.
His current vet did bloodwork to make sure he was healthy - he is - and agreed that he needed something more intense than just supplements as his fear was severe. Funny too because I thought he actually acted pretty decent at the vet - he certainly wasn't at his worst! She was reserved about putting him on Prozac because it can lower bite inhibition. She prescribed Trazodone and Xanax as needed instead.
Like with human meds, it differs totally between dogs and what will work well and what won't. Xanax doesn't seem to work with my Chisum - it makes him super wired and still anxious. Trazodone will need longer to "kick in" so I'll reserve judgement but it mostly just makes him a little sleepy and not really any less anxious. Yesterday my parents left for the weekend (I'm living at home while I finish my degree) and he was a disaster. So, so anxious.
Prozac may work for your dog. Based on what my vet says when I update her in a few weeks, we may or may not give it a go ourselves. Trazodone seems to be more for insomnia and as a supplement to an SSRI so while it seems like a "safe" choice it may not be as beneficial as we'd hoped. It's always worth a try.
Being an SSRI, keep in mind that it will take a while to properly work and the first few weeks might be rough. I have anxiety and depression and take an SSRI for it myself (escitalopram). My docs tapered me up from 5 to 10 to 20mg where I'm at right now. There is benefit to tapering up...the side effects are usually
not as intense. They were really intense when I first started and was adjusting, but were a little less intense when I went up to 10 and when I bumped up to 20 there were almost none. My doc also prescribed a benzo to take the edge off a bit.
So, in dog terms - it may be best to start low and work your way up. It'll take longer to get to that magic dose and you may have little setbacks with each increase but in the long run it may not be as traumatic overall. Your vet may also suggest something for situational anxiety or to give if your dog seems to be struggling.
And, if Prozac doesn't work there are other options out there.
First step is to either talk to a veterinary behaviorist if you have any around (we don't) or see how knowledgeable your current vet is about these kinds of medications. My current vet isn't a veterinary behaviorist but is in contact with one in OH whom she calls for advice - not all vets will do this, but it's helpful. Some vets are more willing than others to prescribe these things, which is sad. Some dogs just have that imbalance, just like us people.
Best of luck to you.