Selective serotonin reuptake inhibitors (SSRIs) are a widely used class of antidepressants that help manage mood and anxiety disorders. They work by increasing the amount of serotonin, a brain chemical linked to mood, in the spaces between nerve cells. SSRIs are commonly chosen as a first-line treatment because they often have a favorable safety profile and are effective for a range of conditions. Like all medicines, they work best when used under medical supervision, with an understanding of how they work, what they treat, what to expect in terms of dosing and side effects, and how to monitor progress and safety over time.
How SSRIs work
SSRIs target a protein called the serotonin transporter (SERT), which normally reclaims serotonin from the space between brain cells. By blocking reuptake, SSRIs keep serotonin available longer in the synaptic gap, supporting signaling pathways that influence mood, anxiety, and emotional regulation. The initial changes in brain chemistry can occur quickly, but noticeable improvements in mood and anxiety often take several weeks. The full benefit may take 4 to 6 weeks or longer for some people. SSRIs are not sedatives and do not produce immediate calming effects; rather, they support long-term regulation of mood and anxiety through complex neural adaptations.
For a broad overview of how these medications work and what they aim to treat, see reputable medical resources such as government and medical organization sections on antidepressants. NIMH overview of antidepressants.
Common uses and conditions treated
SSRIs are prescribed for a range of conditions beyond major depressive disorder. They are often used as first-line therapy for several anxiety disorders and related conditions, as well as some premenstrual and obsessive-compulsive conditions. Common indications include:
- Major depressive disorder (MDD)
- Generalized anxiety disorder (GAD)
- Panic disorder
- Social anxiety disorder
- Obsessive-compulsive disorder (OCD)
- Post-traumatic stress disorder (PTSD)
- Premenstrual dysphoric disorder (PMDD)
In children and adolescents, SSRIs may be used for certain conditions such as OCD and, with careful monitoring, depressive and anxiety disorders. Decisions about treatment type and duration should involve a clinician, taking into account age, medical history, and risk factors. For more on how SSRIs are used in practice, you can review patient information from reputable sources like MedlinePlus. SSRIs: MedlinePlus overview.
Typical dosages
Dosages vary by specific SSRI, individual response, and tolerability. Dosing is usually started at a low level and gradually increased to achieve the desired effect while minimizing side effects. The following are common starting points and typical ranges, but always follow your clinician’s instructions:
- Fluoxetine – starting 10–20 mg once daily; typical range 20–40 mg daily; maximum about 80 mg daily.
- Sertraline – starting 25–50 mg daily; typical range 50–150 mg daily; maximum 200 mg daily.
- Citalopram – starting 10–20 mg daily; typical range 20–40 mg daily; maximum 40 mg daily (often reduced to 20 mg in older adults due to heart-related risks).
- Escitalopram – starting 10 mg daily; typical range 10–20 mg daily; maximum 20 mg daily.
- Paroxetine – starting 10–20 mg daily; typical range 20–50 mg daily; maximum around 60 mg daily in some cases.
- Fluvoxamine – starting around 50 mg daily; typical range 100–300 mg daily; maximum 300 mg daily.
Individual response varies, and it may take several weeks to determine the best dose. Any changes in dose should be made under medical supervision, and abrupt stopping or rapid changes can cause withdrawal-like symptoms.
Potential side effects and monitoring
SSRIs are generally well tolerated, but they can cause side effects for some people. Common, typically early, effects include:
- Nausea, diarrhea, or other GI symptoms
- Headache, dizziness, or fatigue
- Sleep disturbances (insomnia or sleepiness)
- Sexual side effects (reduced libido, difficulty reaching orgasm)
- Dry mouth, sweating, or weight changes
Most side effects lessen over time as the body adjusts. Less common but more serious considerations include:
- Increased risk of suicidal thoughts in children, teens, and young adults, especially early in treatment
- Hyponatremia (low sodium), more likely in older adults
- Serotonin syndrome (a rare but potentially dangerous reaction, especially if combined with other serotonergic medicines)
- Mania or hypomania in people with bipolar spectrum disorders
- Bleeding risk when taken with NSAIDs, anticoagulants, or antiplatelet drugs
Monitoring typically includes regular follow-up with a clinician to assess mood, anxiety symptoms, side effects, sleep, appetite, and any thoughts of self-harm. If new or worsening symptoms develop, contact a clinician promptly. For information on common side effects, the MedlinePlus resource mentioned above offers additional detail. SSRIs: side effects and safety.
Interactions with other medications
SSRIs can interact with other medicines and supplements, which can change how well either drug works or raise the risk of adverse effects. Key considerations include:
- Avoid combining SSRIs with monoamine oxidase inhibitors (MAOIs) or other serotonergic drugs without explicit guidance from a clinician, due to the risk of serotonin syndrome.
- Be cautious with other antidepressants, triptans (for migraines), tramadol, linezolid, and certain supplements like St. John’s wort, which can increase serotonin activity.
- Some SSRIs interact with enzymes in the liver (CYP450 system). For example, fluoxetine and paroxetine can slow the breakdown of other drugs that rely on these enzymes, potentially increasing their effects or side effects. Others have weaker interactions; your clinician will consider these when choosing a medication and dose.
- Bleeding risk may be increased when SSRIs are used with NSAIDs, aspirin, anticoagulants, or antiplatelet drugs.
- Alcohol can worsen some side effects or interact with mood and anxiety symptoms.
Always tell your clinician about all medicines you currently take, including over-the-counter drugs and supplements, so they can check for potential interactions. For a general overview of antidepressants and interactions, see NIMH antidepressants information.
Important considerations for patients
trong> Take medications exactly as prescribed. Do not stop abruptly; discuss any need to discontinue with your clinician and follow a tapering plan to reduce withdrawal symptoms. trong> Symptom relief may take several weeks. If there is no meaningful improvement after 6–8 weeks, talk with your clinician about adjusting the dose or trying a different SSRI or a combination with psychotherapy. trong> In pregnancy and breastfeeding, SSRIs carry specific risks and benefits. Decisions should be made in consultation with a clinician who can weigh maternal health and fetal/neontal considerations. trong> SSRIs may be appropriate for certain conditions such as OCD, but require careful monitoring for mood changes and suicidality. trong> Avoid heavy alcohol use, monitor sleep, exercise, and nutrition, and consider psychotherapy (like cognitive-behavioral therapy) alongside medication for best outcomes. trong> Seek immediate help if you experience severe symptoms such as chest pain, severe dizziness, fainting, confusion, high fever, or muscle rigidity, or if you notice new or worsening thoughts of self-harm.
Resources and practical tips
Reliable patient information can provide additional guidance on choosing and using SSRIs. Consider consulting reputable sources and discussing questions with your clinician. For example:
If you have questions about whether an SSRI is right for you, how to manage side effects, or how to taper off a medication safely, talk with your healthcare provider. Medication is just one part of a comprehensive plan that may also include psychotherapy, lifestyle changes, and social support to improve well-being and daily functioning.
