Complete dosage information for Fenfluramine — threshold, light, common, strong, and heavy dose ranges across 1 route of administration.
Full Fenfluramine profileImportant Safety Notice
Dosage information is for harm reduction purposes only. Individual sensitivity varies greatly. Always start with the lowest effective dose and work your way up slowly. Never eyeball doses — use a milligram scale.
Fenfluramine overdose primarily manifests as serotonin toxicity. The clinical picture can include agitation, confusion, mydriasis (dilated pupils), tremor, muscle rigidity, hyperreflexia, clonus, hyperthermia, tachycardia, hypertension, diaphoresis (excessive sweating), and in severe cases, seizures, rhabdomyolysis, disseminated intravascular coagulation, and death. ## Recognizing an Emergency The most dangerous signs are: - **Hyperthermia** (body temperature above 38.5C/101.3F) -- this is the primary killer in serotonin syndrome - **Muscle rigidity**, especially of the lower extremities - **Seizures** - **Loss of consciousness** - **Rapid, irregular heartbeat** ## What to Do 1. **Call emergency services immediately.** Do not wait to see if symptoms improve. 2. **Cool the person.** Remove excess clothing, apply cool water or ice packs to neck, armpits, and groin. Hyperthermia management is the most critical intervention. 3. **Do not give additional serotonergic drugs.** This includes any SSRI, SNRI, MAOI, tramadol, or other serotonin-active substance. 4. **Benzodiazepines** (if available) can help manage agitation, seizures, and muscle rigidity. 5. **Do not induce vomiting** unless specifically instructed by poison control. ## Medical Treatment Hospital management of severe fenfluramine overdose/serotonin syndrome includes IV benzodiazepines for agitation and seizures, aggressive cooling measures, cyproheptadine (a 5-HT2A antagonist that directly counteracts serotonergic excess), and supportive care. The long half-life of fenfluramine (13-30 hours) and its active metabolite norfenfluramine (34-50 hours) means that monitoring must continue for an extended period -- toxicity can persist or recur for days after a single overdose. ## Long-Term Cardiac Concerns Even if an acute overdose is survived, a single exposure to high-dose fenfluramine may initiate cardiac valvular changes through 5-HT2B activation. Any person who has taken a significant fenfluramine overdose should receive echocardiographic follow-up.
A common oral dose of Fenfluramine is 60–120 mg.
The threshold dose for Fenfluramine via oral is approximately 20 mg.
Fenfluramine typically lasts 8–16 hours via oral.
