Hi, My Husband Started On 30mg Of Duloxetine In May

Hi, my husband started on 30mg of duloxetine in May within 2 weeks he was very agitated, so he was dropped to 20mg. He's been taking 20mg for over a month and the hostility and agitation are back. He went back to provider who put him back up to 30mg, which he hasn't started yet. Why would she up the dose if it didn't work the 1st time, drop him to 20 then back to 30 and at one point wanted him on 60mg?? I also take same med and can't take more than 20mg, but I am very sensitive.