Prozac®, which contains the active ingredient fluoxetine, and Zoloft®, which contains sertraline, are two of the most widely used antidepressants available today.
Prozac and Zoloft are both selective serotonin reuptake inhibitors, or SSRIs. Both medications work by changing the level of serotonin — a neurotransmitter that’s linked to depression — that’s present in your brain.
We’ve explained more about how SSRIs work in our full guide to selective serotonin reuptake inhibitors (SSRIs).
If you’ve been diagnosed with depression or one of several other conditions, your healthcare provider may recommend using Prozac, Zoloft or a similar medication.
Below, we’ve explained how Prozac and Zoloft work, as well as the main differences between these two medications. We’ve also listed side effects, drug interactions and other information that you should be aware of before using either medication.
As SSRIs, Prozac and Zoloft are prescribed to treat similar conditions, albeit with a few small differences and special uses for each drug.
Prozac is also prescribed to treat the eating disorder bulimia nervosa. In combination with the antipsychotic medication olanzapine, it’s also prescribed to treat treatment resistant depression and acute depressive episodes associated with bipolar I disorder.
Zoloft is also prescribed to treat post-traumatic stress disorder (PTSD) and social anxiety disorder (SAD).
Both medications are occasionally prescribed off-label to treat other conditions. For example, generic sertraline — the active ingredient in Prozac — is commonly prescribed off-label to treat premature ejaculation.
Prozac and Zoloft have both been approved by the FDA for use in children and teenagers for certain conditions:
However, it’s important to note that the FDA has issued black box warnings for both Zoloft and Prozac, noting that both medications may increase the risk of suicidal thoughts in children, adolescents and young adults. They also insist parents, guardians and healthcare providers monitor these age groups closely for an increase in, or worsening of, suicidal thoughts.
Prozac and Zoloft can both cause side effects. As with other SSRIs, the most common side effects of Prozac and Zoloft aren’t serious. However, although uncommon, both medications may potentially cause severe side effects and interactions that you should be aware of.
Common side effects of Prozac and generic fluoxetine (affecting five percent of users or more and twice as many users as a non-therapeutic placebo) include:
Common side effects of Zoloft and generic sertraline (affecting five percent of users or more and twice as many users as a non-therapeutic placebo) include:
Prozac and Zoloft are generally safe medications for most people. However, all antidepressants carry some risk of causing serious side effects.
One potential side effect that’s important to be aware of is an increased risk of suicidal thoughts and behavior in children, teenagers and young adults. Prozac and Zoloft both carry a mandatory FDA warning notifying users of this risk in people aged 24 and under.
This risk is most significant during the first few months of treatment, or after changes are made to the medication’s dosage.
Both medications may cause serotonin syndrome — a serious, potentially life-threatening side effect that can occur when they are used with other medications or supplements that increase serotonin levels.
As SSRIs, both medications can also cause issues such as abnormal bleeding, or an increased risk of bleeding, particularly when used with certain blood thinners or NSAIDs.
Both medications can also interact with other drugs, including other antidepressants and widely used prescription medications.
Prozac and Zoloft, as well as their generic equivalents, are both classed as pregnancy category C medications.
This means that animal reproduction studies have shown adverse effects on fetuses, and that there is inadequate research regarding their safety in humans. However, the potential benefits of these medications may warrant their use during pregnancy in certain circumstances.
If you are pregnant or breastfeeding, or plan to become pregnant in the future, it’s important to inform your healthcare provider if you’re currently prescribed Prozac (fluoxetine) or Zoloft (sertraline).
Prozac (fluoxetine) and Zoloft (sertraline) are both effective at treating depression. Research, including several studies, has shown that both medications produce improvements in people with major depression and anxious depression.
One study specifically tested the clinical efficacy of fluoxetine, sertraline and another antidepressant, paroxetine, in 104 patients experiencing major depression and anxious depression, and found no significant differences in the effectiveness of each medication.
Another meta-analysis of 132 randomized controlled trials found that fluoxetine was slightly less effective than sertraline, but researchers also noted that although statistically significant, the clinical meaning of those differences is still uncertain.
As mentioned above, Prozac and Zoloft are also prescribed to treat several other disorders and conditions. If you’re being treated for something other than depression, one medication may be a more suitable choice than the other.
While Prozac and Zoloft have similar side effects, specific side effect rates can differ from one medication to the other. If you get persistent or severe side effects from one medication, your healthcare provider may recommend switching to the other, or to a different antidepressant.
There’s no “best” antidepressant for everyone. It’s normal and common to try several different antidepressants with your healthcare provider before settling on the medication that best suits your symptoms, needs and personal health.
Prozac and Zoloft are both selective serotonin reuptake inhibitors, or SSRIs. There are several other medications in this class, such as Paxil® (paroxetine), Lexapro® (escitalopram), Celexa® (citalopram) and others.
Our guide to SSRIs goes into more detail about antidepressants of this type and lists a range of other medications similar to Prozac and Zoloft.
Many antidepressants are associated with weight gain. As SSRIs, both Prozac and Zoloft are less likely to cause significant weight gain than older types of antidepressant, such as tricyclic antidepressants and monoamine oxidase inhibitors (MAOIs).
In a 2016 study, researchers found that people prescribed fluoxetine and sertraline both gained a small amount of weight (4.6lbs for fluoxetine and 10.5 for sertraline) over the course of two years of treatment.
A separate study published in 2018 found that several of the most commonly prescribed SSRIs and other antidepressants, including the active ingredients in Prozac and Zoloft, caused a higher risk of weight gain during treatment.
In short, antidepressants, including Prozac and Zoloft, can cause weight gain. However, not all people who are prescribed antidepressants will gain weight.
If you are concerned about weight gain while using either antidepressant, talk to your healthcare provider. If suitable for you, your healthcare provider may be able to prescribe an antidepressant that’s less likely to cause weight gain.
Drinking alcohol while you use either Prozac or Zoloft is not recommended. The FDA labels for both medications specifically recommend not to drink alcohol while you are being treated with either medication.
In addition to affecting medication, drinking alcohol may increase your risk of experiencing side effects and/or worsen your depression.
Both Prozac and Zoloft can affect your ability to make decisions, think clearly or react quickly. If you are prescribed either medication, it’s important not to drive, operate heavy machinery or do any other potentially dangerous tasks until you understand how the medication affects you.