High risk — avoid this combination unless there is no good alternative.
Serotonin syndrome: agitation, racing heart, high blood pressure, sweating, tremor, muscle twitching, high body temperature. Can progress within hours to seizures or death if untreated.
Why this happens (mechanism)
Escitalopram (Lexapro) and sertraline (Zoloft) are both SSRIs — they both raise serotonin levels at the synapse. Stacking two SSRIs offers no additional benefit over a single, properly-dosed SSRI but multiplies the risk of serotonin syndrome.
What to monitor
- Body temperature, heart rate, blood pressure
- New tremor, muscle jerks, or hyperreflexia (overactive reflexes)
- Confusion, agitation, or sudden mental status changes
- GI symptoms — diarrhea, nausea
Dose adjustment
Do not combine. If switching between SSRIs, taper the first to a low dose before introducing the second, or use a brief washout period (typically 2-5 days, longer for fluoxetine). When switching is supervised by a prescriber, no overlap is the safest approach.
Safer alternatives to consider
Adequate dose of one SSRI matches or beats two SSRIs at lower doses, with far lower risk.
Combining SSRI + CBT outperforms higher SSRI doses for many anxiety/depression presentations.
Always discuss alternatives with your prescriber before making any change. The right choice depends on your other medications, conditions, and what is working for you today.