A 52-year-old woman with depression is on sertraline 100 mg daily and has well-controlled hypertension on amlodipine 5 mg daily. She develops severe migraine and is prescribed sumatriptan 50 mg as needed. After the second dose of sumatriptan, she experiences agitation, tremor, hyperthermia (38.5°C), and hyperreflexia. What is the most likely diagnosis and the underlying drug interaction?

Explanation

## Serotonin Syndrome: SSRI + Triptan Interaction ### Clinical Presentation The patient presents with the classic triad of serotonin syndrome: 1. **Neuromuscular signs:** Tremor, hyperreflexia, muscle rigidity 2. **Autonomic instability:** Hyperthermia (38.5°C), tachycardia, hypertension 3. **Altered mental status:** Agitation, confusion, restlessness Onset was rapid (within hours of the second sumatriptan dose), which is typical for serotonin syndrome. ### Mechanism of Interaction **Key Point:** Both SSRIs and triptans increase synaptic serotonin. Their combined use creates a supra-physiological serotonergic state in the CNS. **High-Yield:** Serotonin syndrome is a **dose-dependent and time-dependent interaction**: - Risk increases with higher SSRI doses - Risk increases if triptans are used frequently (>2–3 doses per week) - Onset: minutes to hours after the interacting drug is added or dose increased ### Pathophysiology ```mermaid flowchart TD A[SSRI: blocks serotonin reuptake]:::action --> B[Increased synaptic 5-HT] C[Triptan: 5-HT1B/1D agonist + releases 5-HT]:::action --> B B --> D[Excessive 5-HT receptor activation]:::outcome D --> E[5-HT1A overstimulation in brainstem/spinal cord]:::outcome E --> F[Neuromuscular hyperactivity]:::urgent E --> G[Autonomic dysregulation]:::urgent E --> H[Altered thermoregulation]:::urgent ``` ### Hunter Criteria for Serotonin Syndrome (Diagnostic) At least one of the following must be present in a patient taking a serotonergic agent: | Criterion | Examples | |---|---| | **Spontaneous clonus** | Visible muscle jerks without external stimulus | | **Inducible or ocular clonus + agitation or diaphoresis** | Reflex clonus + CNS signs | | **Tremor + hyperreflexia** | Present in this case | | **Hypertonia + hyperthermia + ocular clonus or inducible clonus** | Muscle rigidity + fever + clonus | This patient meets criterion 3 (tremor + hyperreflexia) plus autonomic signs (hyperthermia). ### Management 1. **Immediate:** Discontinue sertraline and sumatriptan 2. **Supportive care:** IV fluids, active cooling for hyperthermia 3. **Benzodiazepines:** Lorazepam 1–2 mg IV for agitation and muscle rigidity 4. **Cyproheptadine:** 12 mg loading dose, then 2 mg every 4–6 hours (non-selective 5-HT antagonist) if severe 5. **Monitoring:** ICU admission if severe; most cases resolve within 24–72 hours of drug discontinuation ### High-Yield: SSRI + Triptan Safety **Clinical Pearl:** The combination of SSRI + triptan is NOT absolutely contraindicated. Risk is low if: - SSRI dose is standard (not high) - Triptan is used ≤2 days per week - Patient is monitored for warning signs **Safer alternatives for migraine in SSRI users:** - Non-triptan abortive: NSAIDs, paracetamol, aspirin - Preventive: Propranolol, topiramate, amitriptyline (tricyclic, not SSRI) **Mnemonic — Serotonin Syndrome Risk Factors: SEROTONIN** - **S**SRIS, SNRIs, TCAs - **E**rgolines (ergotamine) - **R**eversible MAOIs (moclobemide) - **O**ther serotonergics (tramadol, dextromethorphan, St. John's Wort) - **T**riptans - **O**pioids (especially tramadol) - **N**on-selective MAOIs - **I**rreversible MAOIs - **N**ew serotonergic drugs [cite:Harrison 21e Ch 397]