SSRI explained: how these antidepressants work and what to expect

SSRIs (selective serotonin reuptake inhibitors) are a common class of antidepressants that raise serotonin levels in the brain. That simple change can lift mood, reduce anxiety, and help with panic attacks and some chronic pain conditions. If you’re starting an SSRI or helping someone who is, the useful bits are what to watch for, how long effects take, and which meds behave differently.

Common SSRIs and what makes them different

Names you’ll hear a lot: fluoxetine (Prozac), sertraline (Zoloft), citalopram (Celexa), escitalopram (Lexapro), paroxetine (Paxil), and fluvoxamine. Fluoxetine has a long half-life, so missed doses matter less and withdrawal is usually milder. Paroxetine clears faster and often causes stronger discontinuation symptoms when stopped suddenly. Sertraline is a go-to for anxiety and depression because it balances effectiveness and tolerability for many people.

Dosages vary a lot by drug and by person. Doctors usually start low and raise the dose over weeks. Most people notice sleep or appetite changes and some anxiety for the first 1–2 weeks, then mood improvement around 4–6 weeks. If you don’t feel better after 8–12 weeks, talk to your prescriber—adjustments or a different drug may help.

Side effects, risks, and interactions you should know

Sexual side effects (lower libido, delayed orgasm) are common and can be persistent. Other frequent effects: nausea, headaches, sleep changes, and mild weight gain. Watch for more serious signs: sudden confusion, high fever, fast heartbeat, or severe agitation—these could point to serotonin syndrome, especially if you combine SSRIs with triptans, certain migraine meds, MAO inhibitors, or linezolid.

Mixing SSRIs with NSAIDs or blood thinners raises bleeding risk, and some OTC cold meds can interact—if you’re taking imipramine or other older antidepressants, interactions matter a lot. Always tell your pharmacist and doctor about all prescriptions, supplements, and over-the-counter drugs you take.

Tapering off matters. Stopping an SSRI cold turkey can cause dizziness, electric shock sensations, mood swings, and flu-like symptoms. The short-term fix is to taper slowly under a doctor’s plan. Fluoxetine’s long half-life makes tapering easier; paroxetine and venlafaxine (an SNRI) often need a slower, more careful taper.

If side effects are bothering you, there are options: switching to a different SSRI, changing dose, or adding a low-dose med to manage specific symptoms. Some people combine SSRIs with therapy, which improves outcomes more than meds alone.

Final practical point: keep a symptom log for the first 12 weeks—sleep, mood, appetite, sexual side effects, and any new symptoms. That record helps your clinician make faster, smarter decisions. And if you feel suicidal or dangerously unwell at any time, seek emergency help right away.