MEDICATION GUIDES · GUIDE 02
SNRIs
Serotonin–norepinephrine reuptake inhibitors include venlafaxine, duloxetine, desvenlafaxine, and levomilnacipran.
These guides describe patterns across a drug class, not a prediction for one person. Benefits, side effects, interactions, and tapering needs vary by medication, dose, health history, and other treatments. Never start, stop, or change a psychiatric medication without the prescribing clinician.
EVIDENCE REVIEW
SEPTEMBER 24, 2026
How they work—and why dose matters
SNRIs block transporters for serotonin and norepinephrine. Norepinephrine participates in alertness, motivation, stress response, blood pressure, and descending pain-control pathways. That second target helps explain both the pain indications of some SNRIs and the possibility of increased blood pressure or heart rate.
“Dual action” is not identical across the class. Venlafaxine behaves more like an SSRI at lower doses, with more norepinephrine effect at higher doses; levomilnacipran is comparatively more noradrenergic. These are approximate pharmacology rules, not precise personal-response thresholds.
What they are used for
Venlafaxine, duloxetine, desvenlafaxine, and levomilnacipran are approved for major depressive disorder. Venlafaxine also has anxiety-disorder indications. Duloxetine has the broadest label, adding generalized anxiety and several chronic pain conditions. Milnacipran is approved for fibromyalgia in the United States, not depression.
SOURCE · PHARMA LIFE SCIENCES SOURCE · THERAPEUTIC CLASS OVERVIEW
What to expect
- Shared with SSRIs: nausea, dry mouth, sweating, dizziness, headache, sleep change, sexual dysfunction, and possible emotional blunting.
- More class-distinctive: blood pressure and heart rate may rise, especially at higher doses. Blood pressure and pulse should be monitored.
- Other possibilities: tremor, constipation, early appetite reduction, fatigue, nervousness, and urinary hesitation, especially with levomilnacipran.
Timeline and stopping
The broad timeline resembles SSRIs: early change may appear within 1–4 weeks, while fuller benefit often takes 6–8 weeks or longer. Sleep and appetite may improve before energy, motivation, concentration, and mood.
Venlafaxine’s short half-life makes it especially prone to discontinuation symptoms—even after a missed dose. Duloxetine and desvenlafaxine can also be difficult to stop. Symptoms follow the same pattern described for SSRIs—flu-like feelings, sleep disturbance, nausea, imbalance, sensory "brain zaps," and hyperarousal. Tapers need clinician supervision and may take eight weeks or longer; some people need months.
SOURCE · ONSET SUMMARY SOURCE · DISCONTINUATION REVIEW SOURCE · DISCONTINUATION GUIDE
How individual SNRIs differ
These comparisons describe tendencies, not recommendations. A prescriber also weighs diagnosis, other medicines, blood pressure, liver or kidney function, pregnancy plans, and prior response.
