SSRIs: What They Do, Side Effects & How to Stay Safe

SSRIs are the most commonly prescribed antidepressants. People use them for depression, anxiety, OCD, panic disorder and some women use fluoxetine for PMDD. They change how serotonin signals work in your brain, which can lift mood and reduce anxiety — but the effect usually takes 2 to 6 weeks to appear.

How SSRIs work and when they're used

SSRIs block the reuptake of serotonin so more of it stays available between brain cells. Common names you’ll hear: sertraline (Zoloft), fluoxetine (Prozac, Sarafem for PMDD), paroxetine (Paxil). Doctors pick one based on symptoms, side effects and any other meds you take. If one SSRI doesn’t help, switching to another is common and often successful.

Expect a trial period. If you don’t feel better after 6–8 weeks at a therapeutic dose, talk to your prescriber about changing dose or trying a different medicine. Never increase or stop on your own.

Side effects, safety and buying tips

Short-term side effects often include nausea, sleep changes, headache, sweating and reduced sex drive. Many of these ease after a few weeks. A slower, less obvious problem is withdrawal if you stop suddenly — dizziness, flu-like symptoms or mood swings can show up. Taper slowly with your doctor.

Watch for serious issues: if you notice severe mood changes, new suicidal thoughts, or strange bleeding when combined with NSAIDs or blood thinners, contact your prescriber. SSRIs can increase bleeding risk, especially with aspirin or warfarin, so mention all drugs and supplements you take — including St. John's wort, which can interact badly.

If you’re pregnant, breastfeeding, or have bipolar disorder, talk to a specialist. Some SSRIs carry risks in pregnancy and need careful planning. For people having ECT or on tricyclics like dosulepin, doctors often review medication lists since interactions or adjustments may be needed.

Thinking of buying sertraline or other SSRIs online? Be careful. Only use pharmacies that require a prescription and show verification like CIPA or PharmacyChecker. Avoid sites offering high doses without a doctor’s consult. Our site has guides on spotting legit Canadian pharmacies and safe online sellers — use those checklists before you order.

Practical tips: track your mood and side effects with a simple app or notebook, schedule a follow-up 4–6 weeks after starting, never mix with MAOIs, and ask about sexual side effects up front (there are strategies to manage them). If you’re unsure about an online seller, bring the pharmacy info to your clinician before buying.

SSRIs help a lot of people, but they need respect: give them time, watch for side effects, and get prescriptions from trusted sources. Ask questions — your health team expects them and should help you find the safest option.