Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs) are a class of antidepressant
medications used to treat a variety of mood and anxiety disorders. They work by increasing
the levels of two important neurotransmitters in the brain: serotonin and norepinephrine.
These chemicals play key roles in regulating mood, attention, and response to stress. By
blocking the reabsorption (reuptake) of serotonin and norepinephrine into nerve cells,
SNRIs help improve communication between brain cells and alleviate symptoms of
depression and anxiety.
SNRIs are primarily prescribed for major depressive disorder (MDD), generalized anxiety
disorder (GAD), panic disorder, and social anxiety disorder. They are also effective in
managing certain types of chronic pain, such as fibromyalgia, neuropathic pain, and
musculoskeletal pain. Common SNRIs include venlafaxine (Effexor XR), duloxetine
(Cymbalta), desvenlafaxine (Pristiq), and levomilnacipran (Fetzima).
SNRIs are often chosen when selective serotonin reuptake inhibitors (SSRIs) are ineffective
or not well-tolerated. While they share many similarities with SSRIs, SNRIs have the added
benefit of targeting norepinephrine, which can be particularly useful for patients
experiencing fatigue or chronic pain along with depression.
Like all medications, SNRIs can cause side effects. Common ones include nausea, dry
mouth, dizziness, excessive sweating, constipation, and increased blood pressure—
particularly with venlafaxine. Sexual dysfunction, sleep disturbances, and appetite
changes may also occur. These side effects often improve over time, but some may persist
and should be discussed with a healthcare provider.
SNRIs typically take 2 to 4 weeks to begin relieving symptoms, with full effects often taking
up to 6 to 8 weeks. As with other antidepressants, patients are advised not to stop SNRIs
abruptly, as this may lead to discontinuation syndrome, which includes symptoms such
as dizziness, nausea, irritability, and brain "zaps." Tapering off the medication gradually
under medical supervision is recommended.
Though effective, SNRIs may not be suitable for everyone. They should be used cautiously
in individuals with uncontrolled high blood pressure, liver disease, or a history of bipolar
disorder, as they may trigger manic episodes.
