Selective serotonin reuptake inhibitors

SSRIs block the serotonin transporter (SERT) on presynaptic nerve endings, so released serotonin is cleared more slowly and acts longer on its receptors. The block is immediate but mood lifts only after weeks, so slower receptor adaptations are thought to matter; the exact mechanism is unknown. Unlike tricyclics, they barely affect norepinephrine reuptake or muscarinic, histamine and α1 receptors.

• FluoxetineIts very long half-life, with norfluoxetine lasting even longer, means its interactions can continue for weeks after the last dose.
• SertralineIts US license covers PTSD and social anxiety disorder as well as depression, OCD and panic disorder, and it is used for OCD in children from age 6.
• CitalopramIts label carries a specific warning on dose-dependent QT prolongation and torsades de pointes; escitalopram is its active S-enantiomer.
• EscitalopramIt is the single active enantiomer of citalopram; its US label covers depression from age 12 and generalized anxiety disorder in adults.

• Depression
• Generalized and social anxiety disorder
• Panic disorder
• Obsessive-compulsive disorder (OCD)
• Post-traumatic stress disorder (PTSD)
• Bulimia nervosa

• Sexual problems: low libido, delayed orgasmKnown for
• Serotonin syndrome, mainly with other serotonergic drugsKnown forSerious
• Suicidal thoughts in children and young adultsKnown forSerious
• Nausea, loose stools and indigestion
• Low sodium (hyponatremia), mostly in older peopleSerious
• Easy bruising and bleedingSerious
• Gut bleeding, more likely with NSAIDs or aspirinSerious
• QT prolongation (dose-related with citalopram)Serious
• Switch into mania in bipolar disorderSerious
• Discontinuation symptoms if stopped suddenly

What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.

• Never combine with an MAOI: leave 14 days between them (5 weeks after fluoxetine), because of serotonin syndrome.
• Monitor people under 25 closely for worsening mood or suicidal thinking, especially early on and after dose changes.
• Bleeding risk rises with NSAIDs, aspirin, warfarin and other anticoagulants.
• Screen for bipolar disorder first: an SSRI given alone can set off mania.

Written for biofideX in plain words, after checking these references:

• Antidepressants (NHS)
• Selective Serotonin Reuptake Inhibitor (NCI Thesaurus)
• Fluoxetine capsules: label (DailyMed)
• Citalopram tablets: label (DailyMed)

For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.