Fluoxetin toxic dose
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fluoxetine toxic dose overdose mg/kg lethal
Fluoxetine Toxic Dose
Therapeutic range: Fluoxetine (Prozac) is typically dosed 20-80 mg/day. It's one of the safer antidepressants in overdose compared to older TCAs and MAOIs, largely because it has minimal cardiotoxicity and a wide therapeutic index - Kaplan and Sadock's Synopsis of Psychiatry notes it was "significantly safer when taken in overdose than any previously available antidepressant."
Reported toxicity thresholds:
| Population | Dose | Effect |
|---|---|---|
| Adults | Up to 300-400 mg | Maximum tolerated with no toxicity (no co-ingestant) |
| Adults | 1200-2000 mg | Estimated minimum lethal exposure range |
| Adults | ~520 mg (reported case) | Associated with a lethal outcome in at least one case, though survival after 8 g has also been documented - illustrating wide individual variability |
| Children | Up to 3.6 mg/kg | No toxicity observed |
| Children | ~9-19.5 mg/kg | Reported seizures in adolescent case series |
| Children | 26 mg/kg | Seizures and minor ECG changes reported |
| Children | 43 mg/kg | Unresponsiveness, sinus tachycardia, psychomotor agitation |
Serum levels (Harriet Lane Handbook): Levels >1000 ng/mL are considered toxic, though toxicity may occur at levels >300 ng/mL.
Clinical features of overdose (per Tintinalli's Emergency Medicine, which notes fluoxetine has the largest human SSRI overdose experience of any SSRI):
- Mild CNS depression, tremor, nausea/vomiting are most common with isolated SSRI overdose
- Seizures can occur, typically generalized, usually 3-8.5 hours post-ingestion in adolescent case reports
- Serotonin syndrome/toxicity (Sternbach criteria) - agitation, hyperreflexia, clonus, hyperthermia, autonomic instability
- QT/QRS prolongation and arrhythmia (including reported Torsades de Pointes) are rare but described, more often with large ingestions or co-ingestants
- Rhabdomyolysis has been reported with delayed onset
- Death from isolated fluoxetine overdose is rare and usually involves very large ingestions (multi-gram) or co-ingestants (e.g., benzodiazepines)
Key point: Fatal outcomes from fluoxetine alone are uncommon relative to older antidepressants - most fatalities reported in literature involve massive ingestions (>10 g) or combination with other CNS depressants/cardiotoxic drugs.
Management: Supportive care, activated charcoal if presenting early, cardiac monitoring/ECG for QT prolongation, benzodiazepines for seizures or agitation, and cyproheptadine for serotonin syndrome if it develops.
Recent case reports (PMID: 37957092, 30301727) reinforce that seizures and serotonin toxicity are the main concerns in adolescent overdoses even at moderate doses (600-1200 mg, ~10-20 mg/kg), and a case of fatal Torsades de Pointes (PMID: 30214811) shows cardiac risk isn't zero even though it's rare. These don't contradict the textbook consensus but add nuance - individual susceptibility varies significantly.
- Tintinalli's Emergency Medicine, p. (Clinical Features, SSRI overdose section)
- Kaplan and Sadock's Synopsis of Psychiatry (SSRIs section)
- The Harriet Lane Handbook, 23rd ed.
Is fluoxetin 120mg toxic dose for 19yr old 45kg female
Dose calculation: 120 mg ÷ 45 kg = 2.67 mg/kg
Based on the toxicity data reviewed:
-
Not typically classified as a severe/lethal overdose. For comparison:
- Up to 3.6 mg/kg has been reported with no toxicity in children/adolescents.
- Toxic effects (seizures, agitation) have been reported starting around 9-19 mg/kg in adolescents.
- Estimated minimum lethal exposure in adults starts around 1200-2000 mg total (roughly 27-44 mg/kg for a 45 kg person) - far above 120 mg.
- The "maximum tolerated dose with no toxicity" cited for adults is 300-400 mg, and this ingestion (120 mg) is well below that.
-
120 mg is about 1.5x the usual maximum therapeutic daily dose (80 mg) for fluoxetine. This is a mild-to-moderate excess, not typically a life-threatening ingestion in isolation.
What to expect: At this dose, the most likely effects are mild - nausea, tremor, drowsiness, restlessness, or anxiety. Seizures, serotonin syndrome, or cardiac effects are unlikely at 2.67 mg/kg but not impossible, especially if there are co-ingestants (alcohol, other serotonergic drugs, other medications) or the person has other risk factors.
Important safety guidance regardless of the numbers:
- If this dose was actually taken (intentionally or accidentally) by a real person, contact Poison Control (in the US: 1-800-222-1222) or go to an emergency department for assessment - especially to rule out co-ingestion and to monitor for serotonin toxicity (agitation, tremor, hyperreflexia, fever) over the next 6-8 hours, which is the typical window for symptoms to emerge.
- If this was an intentional overdose, that itself is a medical and mental health emergency that needs in-person evaluation - dose calculations alone shouldn't be used to decide whether to seek care.
- ECG monitoring is reasonable given rare reports of QT/QRS changes even with SSRIs.
If this relates to an actual current situation, please seek emergency medical evaluation now rather than relying on this estimate.
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