Fluoxetine dosages are determined by age, the condition being treated, and the type of formulation of the drug. They are also impacted by patient response, as this is the most reliable means of determining drug and dose efficacy. Patients might take other medications that may impact response or directly influence the way fluoxetine, often sold under the name Prozac®, works and is metabolized by the body. In these cases, dosages could require adjustment.
The first consideration is the age of the patient, and usually the drug is not given to children under the age of seven. Children over seven through their mid-teens could receive fluoxetine dosages that vary from 10 to 60 mg for conditions like major depression, obsessive-compulsive disorder (OCD) or bulimia nervosa. Younger children generally receive lower doses, but the condition is also a strong influence. OCD dosage can climb to 60 mg in the under-18 population, but dosages for depression in children usually don't exceed 20 mg. Like many antidepressants, fluoxetine usually begins with a lower dose and is increased over a few weeks to a maintenance dose.
Age also impacts dosage amount in another way. If fluoxetine is used in the geriatric population, the doses are usually smaller than "adult" doses. Recommendations for this population may more closely resemble recommendations for children.
Adults with a variety of conditions take fluoxetine dosages that are partly based on the condition and on their response to the drug. Initiation therapy typically begins at 20 mg, though with conditions like panic disorder, the initial recommended dose is 10 mg. In major depressive disorder, many patients respond favorably to the starting dose of 20 mg, but if this insufficient, dosages can climb to a maximum of 80 mg per day. With OCD, patients tend to have therapeutic benefits with drug levels of 20 to 60 mg, but some patients may take up to 80 mg.
Individuals with bulimia tend not to respond to fluoxetine dosages below 60 mg. A very different dosing schedule is recommended for women with premenstrual dysphoric disorder. They may take 20 to 60 mg for the 14 days each month prior to the onset of their periods.
Another option for dosing is available with a pill known as "weekly Prozac®." This drug may be appropriate for people who have stabilized conditions that don't appear to require daily treatment. It is taken once a week, usually in 20 mg amounts.
Certain medications used in combination with fluoxetine may impact the way the body reacts to or clears the drug. One of these is olanzapine, an atypical antipsychotic, which is sometimes prescribed with fluoxetine to address treatment resistant depression in major depressive disorder and bipolar disorder. The wisdom of using fluoxetine in bipolar is questionable given its potential to induce manic and hypomanic states, but the practice is not unknown. The therapeutic range for is 25 to 50 mg when olanzapine is used, and the two drugs are available in a combination pill.