Switching From Zoloft (Sertraline) To Prozac (Fluoxetine)

In our latest question and answer, the pharmacist discusses switching from Zoloft (sertraline) to Prozac (fluoxetine).


I was just reading the article on switching from one antidepressant to another. My doctor is trying to wean me off Zoloft (sertraline) but instead of taking me slowly down, she switched me to Prozac at a lower dose. I don't understand why she did that. Why didn't she just lower the sertraline little by little to wean me off of it? Do you know why that would be? My primary care physician is the one doing all this. Its her plan to wean me off sertraline. This is really messing with my head. Sertraline was 100mg now I'm on Prozac 20 mg. Can you help so I can tell her what I would rather do?

Asked by Jacks On Jul 02, 2018

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Jul 02, 2018

Antidepressant PackThere is no single recommended way to switch antidepressants, and there are a variety of methods that can utilized.

Before we discuss the two most common methods for switching from one SSRI (selective serotonin re-uptake inhibitor) to another, I want to point out that many patients do find that switching between different drugs in the same class (from Zoloft to Prozac in this example) can be effective. Studies have shown that most individuals are equally as likely to respond to another drug in the same class as switching to another class.

Cross-Tapering SSRIs

Some practitioners recommend a "cross-taper" method, which is most likely what you read in one of our other articles. With a cross-taper method, one SSRI is slowly decreased, while at the same time, starting at a low dose and gradually increasing the new SSRI.

Some sources recommend a "cross-taper" when switching between different classes of antidepressants, to avoid withdrawal symptoms and symptom re-occurrence. However, the direct switch method is used just as often, if not more so, when going from one SSRI to another SSRI since we aren't as concerned with withdrawal effects due to the same mechanism of action.

Direct Switch On SSRIs

When switching between agents in the same class of medication, such as from Zoloft (sertraline) to Prozac (fluoxetine), a direct switch is commonly utilized, which is what your doctor is doing, and is supported by multiple studies. A direct switch is done by:

  • Stop the SSRI you are currently taking (Zoloft in your case).
  • Start the new SSRI at a low dose (typically Prozac 20 mg every other day or every day).

If were taking a high dose of the Zoloft (>100 mg), it may be prudent to taper to a lower dose before starting the new agent to avoid increasing your risk of serotonin syndrome. However, this is can be mitigated as well by starting your new SSRI on a low dose, as your practitioner has done.

The only time a direct switch from one SSRI to another isn't recommended is if you are initially taking Prozac. Prozac has a very long half-life and after discontinuing, can last in the body for an extended period of time (weeks for some individuals). Typically, a seven-day "washout" period is advised, meaning to stop Prozac, wait 7 days, and then start the new SSRI.

Additional Information

As stated at the beginning, there is no single right or wrong way to switch SSRIs and the method your doctor recommends will be based on your personal medical history and their professional experience, knowledge and judgement. If you are concerned with the method being used to switch you from Zoloft to Prozac, be sure to speak with them to come up with an appropriate treatment plan.

About the Pharmacist

Dr. Brian Staiger Pharm.D

Dr. Brian Staiger is a licensed pharmacist in New York State and the founder of PharmacistAnswers.com. He graduated from the University At Buffalo with a Doctor of Pharmacy degree in 2010. He has been featured in numerous publications including the Huffington Post as well as a variety of health and pharmacy-related blogs. Please feel free to reach out to him directly if you have any inquiries or want to connect! He's answered thousands of medication and pharmacy-related questions and he's ready to answer yours! Brian.Staiger@PharmacistAnswers.com Office: 716-389-3076

About Zoloft (Sertraline)

Zoloft (sertraline) (pronounced SER tra leen) is used to treat depression. It may also be used to treat obsessive compulsive disorder, panic disorder, post-trauma stress, premenstrual dysphoric disorder (PMDD) or social anxiety. It is classified as a SSRI, selective serotonin re-uptake inhibitor, which work by increasing the availability of serotonin in the brain as well as changing the balance of serotonin receptors over time. Zoloft may be taken without regard to meals in the morning or evening. Like many antidepressants, full effects of the drug may not be realized for 6-8 weeks.

About Prozac (Fluoxetine)

Prozac (fluoxetine) is a selective serotonin reuptake inhibitor (SSRI) and is most commonly used for the treatment of depression. It is also used to treat anxiety and panic disorders. SSRI medications, like Prozac, work by increasing the amount of the neurotransmitter serotonin in the brain. Prozac typically needs to be dosed consistently for 4-6 weeks for the effects of the medication to be noticed. While effective, Prozac is associated with a variety of potential side effects such as weight fluctuations (gain and loss), headache, dizziness, QT prolongation and sexual dysfunction. Prozac is dosed once every 24 hours and can be taken with or without food. One interesting characteristic of Prozac is that it has an extremely long half-life, around 4 to 6 days. For this reason, it is associated with less withdrawal reactions than other antidepressants with shorter half-lives.

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