Prozac vs Lexapro: SSRIs compared
Prozac (fluoxetine) and Lexapro (escitalopram) are both SSRI antidepressants. Fluoxetine stays in the body for weeks, which softens withdrawal but means more interactions linger; escitalopram has fewer interactions and is approved for generalized anxiety as well as depression.
Updated October 4, 2026
At a glance
- Approved for
- Prozac
- Depression, OCD, panic disorder, bulimia
- Lexapro
- Depression and generalized anxiety disorder
- How long it lasts
- Prozac
- Weeks after stopping
- Lexapro
- Days after stopping
- Drug interactions
- Prozac
- More: strongly blocks the CYP2D6 enzyme
- Lexapro
- Fewer
- Common early effects
- Prozac
- More often activating: restlessness, trouble sleeping
- Lexapro
- More often mild drowsiness or nausea
- Generic
- Prozac
- Yes
- Lexapro
- Yes
Prozac fluoxetine | Lexapro escitalopram | |
|---|---|---|
| Approved for | Depression, OCD, panic disorder, bulimia | Depression and generalized anxiety disorder |
| How long it lasts | Weeks after stopping | Days after stopping |
| Drug interactions | More: strongly blocks the CYP2D6 enzyme | Fewer |
| Common early effects | More often activating: restlessness, trouble sleeping | More often mild drowsiness or nausea |
| Generic | Yes | Yes |
The long half-life
Fluoxetine and its active breakdown product remain in the body for weeks. That makes missed doses and stopping gentler, with fewer withdrawal symptoms, but it also means at least five weeks must pass after stopping fluoxetine before an MAOI can be started, and its interactions persist after the last dose. Escitalopram clears within days.
Interactions
Fluoxetine strongly blocks the enzyme CYP2D6, so it raises levels of medicines such as metoprolol and some antidepressants and reduces the effect of tamoxifen. Escitalopram has fewer interactions, which can matter for people on several medicines. Both carry the usual SSRI cautions: serotonin syndrome with other serotonin-affecting medicines and more bleeding with blood thinners or anti-inflammatories.
Choosing
Fluoxetine is often taken in the morning because it can be activating, and its approvals include OCD, panic disorder and bulimia. Escitalopram is often chosen when anxiety is prominent or interactions are a concern. Both are used in young people, with approvals that differ by condition and age, and both carry a warning about suicidal thoughts in young people.
Cost
Both are inexpensive generics, and 90-day supplies usually cost less per day.
How long until they work
Both usually take two to four weeks to start helping and six to eight weeks for the full effect, so prescribers usually wait before changing the dose or switching. Switching between SSRIs is common and generally straightforward, though the long half-life of fluoxetine means a switch away from it is planned around that.
Questions for your prescriber
- Do my other medicines interact with either?
- Is my anxiety, OCD or sleep a reason to prefer one?
- How long should I take it before judging whether it works?
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Sources
Written by the Script Unlock editorial team from the sources above. It is general information, not advice for you or your pet; your prescriber decides which medicine is right.
Script Unlock is a marketplace that lets licensed pharmacies quote a cash price on your prescription. It does not prescribe, dispense or sell medication, does not process patient payments, and does not give medical advice. Always follow the instructions of your prescriber and pharmacist and read the medication guide supplied with your medicine.