Management of Paroxetine 125 mg + Clonazepam 2.5 mg Ingestion

Clinical Alert: These are supratherapeutic doses. Paroxetine's usual therapeutic range is 10-60 mg/day (up to 60 mg), and clonazepam's usual dose is 0.25-2 mg/day for anxiety (up to 20 mg in refractory epilepsy). A 125 mg paroxetine + 2.5 mg clonazepam combined ingestion must be treated as a mixed overdose requiring immediate clinical assessment.

Step 1 - Immediate Stabilization (ABC)

• Airway: Assess level of consciousness (GCS). Both drugs cause CNS depression; the combination significantly increases respiratory depression risk.
• Breathing: Monitor respiratory rate and oxygen saturation. Use end-tidal CO2 monitoring. Be prepared for endotracheal intubation if respiratory depression develops. Initial stabilization should not be delayed to give an antidote.
• Circulation: Establish IV access. Monitor ECG continuously - paroxetine (an SSRI) can cause QTc prolongation at toxic doses.
• Vitals: Monitor temperature, BP, HR, and SpO2 closely.

Step 2 - Clinical Assessment for Key Syndromes

A. CNS/Respiratory Depression (Primarily Clonazepam)

• Sedation, drowsiness, slurred speech, ataxia
• Respiratory depression (typically mild to moderate with benzodiazepines alone)
• Profound coma is rare with pure benzodiazepine overdose - if it occurs, suspect coingestants

B. Serotonin Syndrome (Primarily Paroxetine - SSRI toxicity)

• Neuromuscular abnormalities: tremor, clonus (especially ankle clonus), hyperreflexia, myoclonus, rigidity
• Autonomic instability: tachycardia, diaphoresis, hyperthermia, labile BP
• Altered mental status: agitation, confusion

Note: Clonazepam, being a benzodiazepine (GABAergic), may actually mask early serotonin syndrome signs by reducing neuromuscular excitability, making assessment more challenging.

Step 3 - Gastrointestinal Decontamination

• Activated charcoal: Consider if patient presents within 1-2 hours of ingestion and has a protected airway (GCS intact, no aspiration risk). Paroxetine is amenable to charcoal adsorption.
• Gastric lavage: Not routinely recommended for benzodiazepines; may be considered for large recent paroxetine ingestion.
• GI decontamination is NOT indicated in isolated benzodiazepine overdose per Rosen's Emergency Medicine.

Step 4 - Antidote Decisions

Flumazenil for Clonazepam Component

No antidote exists for paroxetine/SSRI toxicity.

Step 5 - Serotonin Syndrome Management (if features present)

1. Discontinue paroxetine immediately (and any other serotonergic agents)
2. Benzodiazepines liberally - treat psychomotor agitation and neuromuscular hyperexcitation. Heat generation in serotonin syndrome is entirely peripheral; controlling neuromuscular abnormalities prevents life-threatening hyperthermia.
3. Cyproheptadine (5-HT2A antagonist): for mild-to-moderate serotonin syndrome - initial dose 12 mg orally, then 2 mg every 2 hours until response. Not useful in severe or critically ill patients.
4. Temperature control: If hyperthermia present, use evaporative cooling (spray water + fans). Antipyretics (paracetamol, etc.) are NOT effective since heat is from muscle activity, not central resetting.
5. Severe cases: Intubation + deep sedation. Nondepolarizing neuromuscular blockers (e.g., vecuronium) as last resort for refractory rigidity - never succinylcholine (risk of fatal hyperkalemia from rhabdomyolysis).

Step 6 - Monitoring and Investigations

Step 7 - Disposition

• All patients with supratherapeutic ingestion of both drugs should be admitted for monitoring for at least 12-24 hours, given clonazepam's long half-life (18-50 hours).
• ICU admission if: respiratory depression, serotonin syndrome features, altered mental status, hemodynamic instability.
• Psychiatric evaluation is essential once medically stable (intentional overdose must be assessed).

Summary at a Glance