How Safe Is Taking Lexapro Over Prozac For Depression?

I had to switch from lexapro to prozac due to cost. Been taking the prozac for allmost 60 days @40 mg.The last two weeks have been suffering with sévère depression and anxiety attacks.Saw my Md. 3 days ago, increased m y prozac to 60 mgs.Should i give this time to work? Or should I go back to lexapro ? I do have 0 5 of zanex. 4 à day. Anxiety attacks are Really getting bad.