Would taking 20 mg of Prozac (fluoxetine) every other day be like taking 10 mg every day?

Yes. Prozac (fluoxetine) has a. very long half-life and its active metabolite also has a long half-life which means it is active in the body for a long time. Therefore taking 20 mg of Prozac (fluoxetine) every other day would be like taking 10 mg every day. Best regards.