Pharmacokinetics of Sertraline

Absorption and Peak Concentration

• Oral absorption is efficient, with peak plasma concentrations in 4.5 to 8.4 hours.

Metabolism of Sertraline

• Hepatic metabolism primarily via CYP2B6, CYP2C19, and CYP3A4.

• Metabolized to N-desmethylsertraline, a minimally active metabolite.

Half-Life of Sertraline

• Sertraline: ~26 hours

• N-desmethylsertraline: 62–104 hours

Excretion of Sertraline

• Primarily excreted as metabolites via feces (40–60%) and urine (~12–14%)

Bioavailability of Sertraline

• Absolute oral bioavailability: ~44% due to significant first-pass metabolism.

Mechanisms of Sertraline Toxicity

Toxicity stems from excessive serotonin reuptake inhibition, increasing serotonergic neurotransmission. High doses or co-ingestion with other serotonergic or CNS-active agents (e.g., MAOIs, lithium, alcohol) may lead to serotonin syndrome, CNS depression, seizures, cardiovascular instability, and hyponatremia (SIADH) (Liu et al., 1996; Jacob & Spinler, 2006; Joseph et al., 2024)

Toxic Dose of Sertraline

Pediatric Threshold

• Ingestion of >250 mg in children <6 years is a concern (Klein-Schwartz et al., 2012).

• Doses <250 mg generally cause no or mild symptoms.

Adult Threshold

• Risk increases with ingestion of >5× the prescribed dose (e.g., >250 mg if daily dose is 50 mg).

• Co-ingestion with other serotonergic or CNS depressants elevates toxicity risk (Isbister et al., 2004; Cooper et al., 2022).

Sources of Sertraline

• Available as Zoloft® and generics.

• Common formulations: 25 mg, 50 mg, 100 mg tablets; oral concentrate.

• Exposures occur through intentional overdose, pediatric exploratory ingestion, or therapeutic error.

Therapeutic and Toxic Serum Sertraline Concentrations

• Therapeutic: ~30–200 ng/mL (rarely measured clinically)

• Toxic: >400–500 ng/mL may be associated with toxicity; poor correlation with severity

Clinical Presentation and Signs and Symptoms of Sertraline Toxicity Based on Severity

Mild Sertraline Toxicity

• Drowsiness, dizziness

• GI upset: nausea, vomiting, constipation, diarrhea

• Agitation, restlessness

• Mydriasis

• Mild tachycardia, hypertension

• Cutaneous vasodilation

• Mild electrolyte shifts (e.g., hypochloremia)

Moderate Sertraline Toxicity

• Persistent agitation, tremor

• Palpitations, hyperreflexia

• SIADH → mild to moderate hyponatremia

• ALT/AST elevation (100–1000 IU/L)

Severe Sertraline Toxicity

• Serotonin syndrome: clonus, hyperreflexia, altered mentation

• Seizures, CNS depression/coma

• Hemodynamic instability: hypotension, dysrhythmias

• Severe hyponatremia, respiratory failure

Cardiac Monitoring and Toxicology Consultation

Although sertraline is less cardiotoxic than other SSRIs or tricyclic antidepressants, QT interval prolongation has been reported in rare cases of severe overdose, particularly with co-ingestants or in patients with underlying cardiac risk factors (Isbister et al., 2004). Continuous cardiac monitoring and serial ECGs should be considered in patients with syncope, palpitations, or known long QT syndrome.

A toxicology consultation or poison control referral is strongly recommended in the following scenarios:

·       Seizures or recurrent neurologic symptoms

·       Persistent or worsening serotonin syndrome despite benzodiazepine therapy

·       Severe hyponatremia or refractory SIADH

·       QTc prolongation or ventricular dysrhythmias

·       Ingestion of multiple serotonergic agents, including MAOIs, TCAs, or lithium

·       Diagnostic uncertainty, especially in atypical presentations or polypharmacy

In these cases, expert input can assist with risk stratification, antidotal therapy consideration, and disposition planning (McDaniel, 2001), (Frye et al., 2019).

Management of Sertraline Toxicity Based on Severity

Mild Sertraline toxicity

• Supportive care

• Activated charcoal if within 1 hour of ingestion

• Benzodiazepines as needed for anxiety or agitation

Moderate Sertraline toxicity

• Observation in a medical facility

• Activated charcoal for early-presenting patients

• Benzodiazepines for agitation or tremor

• Lab monitoring: LFTs, electrolytes, ECG

Severe Sertraline toxicity Management

· Airway protection and intubation if the patient has decreased consciousness, severe hyperthermia, or is unable to protect their airway.
• Activated charcoal may be administered after intubation if the patient presents within 1 hour of ingestion.
• IV benzodiazepines (e.g., lorazepam or diazepam) are first-line for agitation, seizures, and muscle rigidity.
• IV fluids support volume status, renal perfusion, and hyperthermia management. Use isotonic solutions cautiously in SIADH.
• External cooling is recommended for temperature ≥38.5°C.
• Neuromuscular paralysis with intubation (e.g., non-depolarizing agents) is indicated for severe hyperthermia (>41°C) or rigidity unresponsive to sedation.
• ICU admission is warranted for patients with seizures, respiratory failure, or hemodynamic instability.
• IV lipid emulsion therapy may be considered only in refractory dysrhythmia or cardiovascular collapse, in consultation with a toxicologist. Use is extrapolated from lipophilic drug toxicity, with no controlled trials in SSRIs (Jamaty et al., 2010; Gosselin et al., 2016).
• Consider cyproheptadine for moderate to severe serotonin syndrome not responding to supportive care (see below).

Antidote for Serotonin Syndrome: Cyproheptadine

·       Supportive care with IV fluids and benzodiazepines remains the cornerstone of serotonin syndrome treatment.

·       Cyproheptadine, a 5-HT2A antagonist, may be used as adjunctive therapy when symptoms persist despite appropriate supportive care.

Note: Use is based on case reports and expert consensus. No randomized controlled trials support efficacy. Rated as Level C evidence.

Cyproheptadine Dosing Regimen:

Initial dose: 12 mg orally or via NG tube

Maintenance: 2 mg every 2 hours as needed until symptom improvement

Then 4–8 mg every 6–8 hours (Graudins et al., 1998)

Evidence-Based Summary

QT Prolongation and Cardiac Monitoring

·       Although sertraline is rarely cardiotoxic, QTc prolongation has been reported in rare severe overdoses, particularly with co-ingestants or pre-existing cardiac disease (Isbister et al., 2004).
Recommendations:

·       Obtain baseline and serial ECGs every 4–6 hours if:
 – QTc >470 ms
 – Syncope or palpitations are present

·        Monitor and correct K⁺, Mg²⁺, and Ca²⁺ to reduce arrhythmia risk (Gosselin et al., 2016).

Observation Criteria

Children

• Refer to ED if:

  • Ingested >250 mg

  • Any symptoms present

  • Co-ingestants involved

• Discharge if asymptomatic after 6–12 hours

Adults

• Observe if:

  • Ingested >5× prescribed dose

  • Symptomatic or co-ingestants involved

• Discharge if stable and symptom-free after 6–12 hours

Prevention and Public Health Measures

• Childproof packaging, keep medications out of reach

• Blister packaging to deter pediatric ingestion

• Educate patients on medication adherence and overdose risks

• Monitor high-risk patients for suicidal ideation

• Promote safe prescribing practices and avoid serotonergic polypharmacy