Does Seroquel Cause Serious Mood Swings And Irregular Heart Beats?

I'm worried about my brother who has started taking seroquel 300 mg at night. He is also on mirtazapine 90mgs and takes 2 sleeping tablets at night along with a fortnightly depot antipsycotic of flupenthixol. Since taking the seroqul he has had some serious mood swings of impending doom which luckily don't last too long and he has also has had some intermittent breathing difficulties (he is a heavy smoker). Tonight he rung me with this impending doom feeling again and also said that is heart was beating irregular. My brother phoned his psychiatrist and told him about the impending doom and he said that seroquel doesn't do that and that it was a panick attack, but I don't think this is the case. I've read some terrible things about seroquel and am very converned. I think he's on too many drugs. Can you give me your opinion.