Substance Use and Toxicology

Learning objectives

After completing this chapter, you should be able to use respectful, person-centered language; distinguish screening from toxicology testing; recognize common toxidromes; manage opioid, stimulant, sedative-hypnotic, alcohol, and selected medication poisonings; avoid abrupt disruption of medications for opioid-use disorder; anticipate maternal, fetal, and neonatal effects; and select safe transport monitoring, antidotes, and destination capability.

Opening transport scenario

A 30-year-old patient at 31 weeks is transferred after being found somnolent with slow respirations. Respiratory rate is 6/min, SpO₂ is 82%, pupils are small, and fetal heart rate is 105/min. A partner reports that the patient takes prescribed buprenorphine but may also have taken an unknown counterfeit tablet. The immediate priority is not to determine whether the exposure was prescribed, illicit, intentional, or accidental. The priority is effective ventilation, oxygenation, naloxone when indicated, glucose and temperature assessment, ECG monitoring, and rapid identification of coingestants.

1. Person-centered toxicology care

Substance use disorder is a medical condition, not a moral failure. Use neutral terms such as substance use, positive toxicology result, opioid use disorder, and medication treatment. Avoid stigmatizing labels. Interview privately when feasible, ask what was taken rather than demanding admission of “abuse,” and explain why questions or tests are clinically relevant.

• Stabilize airway, breathing, circulation, temperature, and glucose before pursuing a complete exposure history.
• Ask about prescribed medications, over-the-counter products, supplements, alcohol, nicotine, cannabis, and nonprescribed substances.
• Determine substance, dose, route, timing, formulation, intent, tolerance, and possible coingestants.
• Request containers, medication lists, ECGs, laboratory results, and poison-center recommendations.
• Assess for self-harm risk, coercion, intimate-partner violence, withdrawal risk, and access to ongoing treatment.

2. Screening, toxicology testing, and interpretation

Universal verbal screening with a validated tool is different from biologic testing. Screening identifies risk and opens a pathway to treatment. A urine or blood result detects selected substances or metabolites within a limited window; it does not establish impairment, dose, timing, frequency, a substance-use-disorder diagnosis, intent, or parenting ability.

Explain testing and obtain consent according to applicable law and policy. ACOG recommends consent for drug testing and cautions against punitive or biased testing. Treatment must never be delayed while awaiting a toxicology panel.

3. Opioids: overdose, withdrawal, and opioid-use disorder

Opioid overdose

Respiratory depression is the immediate threat. Open the airway, assist ventilation with oxygen, apply waveform capnography when available, and administer naloxone according to protocol. Naloxone should not be withheld from a pregnant patient with suspected life-threatening opioid toxicity. Titrate to adequate ventilation rather than to full arousal when feasible, while anticipating agitation, vomiting, recurrent respiratory depression, and precipitated withdrawal.

• Consider fentanyl or other potent synthetic opioid exposure when recurrent or profound depression occurs.
• Observe for renarcotization because naloxone may wear off before the opioid.
• Evaluate for aspiration, pulmonary edema, trauma, hypoglycemia, and coingestants.
• Use fetal monitoring after maternal stabilization when gestational age and resources permit.

Withdrawal and medication treatment

Do not abruptly stop methadone or buprenorphine during transport. Withdrawal can cause maternal distress, vomiting, dehydration, sympathetic activation, relapse risk, and fetal stress. Confirm the medication, dose, last administration, prescriber, and receiving plan. Routine medically supervised withdrawal is generally not preferred to ongoing medication treatment for opioid-use disorder in pregnancy.

4. Cocaine, methamphetamine, and other sympathomimetics

Severe sympathomimetic poisoning can produce agitation, hypertension, tachycardia, coronary vasospasm, dysrhythmia, seizures, hyperthermia, rhabdomyolysis, acidosis, stroke, placental abruption, preterm labor, and fetal compromise.

• Reduce stimulation and use benzodiazepines for severe agitation or seizures according to protocol.
• Treat life-threatening hyperthermia with rapid active cooling; antipyretics do not correct toxin-generated heat.
• Monitor ECG, temperature, glucose, electrolytes, renal function, creatine kinase, acid–base status, and fetal status.
• For coronary vasospasm or severe hypertension, follow toxicology and medical-control guidance regarding vasodilator therapy.
• Do not attribute chest pain or neurologic deficit to anxiety.

5. Sedative-hypnotics, alcohol, and withdrawal

Sedative-hypnotic toxicity

Benzodiazepines, barbiturates, sleep medications, alcohol, gabapentinoids, and other sedatives often cause CNS and respiratory depression. Management is primarily supportive: airway positioning, ventilation, oxygenation, aspiration precautions, temperature control, and evaluation for coingestants. Flumazenil has important seizure and withdrawal risks and should be used only under a specific toxicology-guided indication.

Alcohol withdrawal

Alcohol withdrawal can cause tremor, autonomic hyperactivity, hallucinations, seizures, and delirium. Benzodiazepines remain the principal treatment for significant withdrawal, including in pregnancy when clinically indicated. Give thiamine early when chronic alcohol use or malnutrition is suspected; correct hypoglycemia promptly and do not delay glucose for life-threatening hypoglycemia.

Cannabis and synthetic cannabinoids

Cannabis exposure may be associated with anxiety, tachycardia, impaired judgment, vomiting, or cannabinoid hyperemesis. Synthetic cannabinoids can cause severe agitation, seizures, hypertension, kidney injury, or unpredictable mixed toxidromes. Treatment is supportive and symptom-directed. Counseling should be nonpunitive and evidence-based.

6. Selected medication and environmental poisonings

Decontamination is exposure-specific. Do not induce vomiting. Activated charcoal may be considered for selected recent ingestions when the airway is protected and toxicology guidance supports it. Contact Poison Help in the United States at 1-800-222-1222 or the relevant regional poison center early.

7. Maternal, fetal, and neonatal implications

• Maternal hypoxemia and hypotension reduce uteroplacental perfusion.
• Stimulant vasoconstriction and hypertension can be associated with placental abruption and fetal compromise.
• Hyperthermia, seizures, and severe acidosis increase maternal and fetal metabolic stress.
• Near delivery, opioids and sedatives may produce neonatal respiratory depression; prepare neonatal support.
• Chronic opioid exposure can lead to neonatal opioid withdrawal; this is not treated by withholding maternal medication treatment.

8. Toxicology transport plan

• Carry enough antidote, sedation, airway, cooling, glucose, and infusion resources for the entire mission plus delay.
• Repeat ECGs, temperature, glucose, ventilation, mental status, and perfusion at clinically appropriate intervals.
• Trace all infusions and document last antidote dose, response, and expected redosing time.
• Choose a destination with obstetric, critical-care, toxicology, dialysis, ECMO, or neonatal capability based on the anticipated rescue.
• Define diversion triggers: recurrent apnea, refractory seizure, dysrhythmia, hyperthermia, shock, worsening QRS, fetal bradycardia, or imminent birth.

9. Evolving case study

Phase 1: Ventilation first

The team provides bag-mask ventilation with oxygen and administers naloxone. Respiratory rate rises to 12/min, EtCO₂ improves, and fetal heart rate returns to 135/min. Full arousal is not required to demonstrate successful reversal.

Phase 2: Recurrent depression

Twenty-five minutes later the patient again becomes somnolent. Repeat naloxone is required, supporting a longer-acting or high-potency opioid exposure. The team prepares an infusion according to protocol and confirms that the receiving facility can provide maternal critical care and neonatal support.

Phase 3: Treatment continuity

The team documents prescribed buprenorphine without labeling it as the cause of the overdose. Addiction-treatment information is communicated with consent and appropriate confidentiality protections. The plan includes overdose treatment, coingestant evaluation, and continuation of evidence-based opioid-use-disorder care.

10. High-yield chapter summary

1. Treat physiology and toxidrome before waiting for a drug screen.
2. Use respectful, nonpunitive communication.
3. Biologic testing has major limitations and generally requires informed consent.
4. Ventilation is the priority in opioid overdose; naloxone should not be withheld because of pregnancy.
5. Continue methadone or buprenorphine unless a specific clinician-directed reason exists to change therapy.
6. Benzodiazepines are central to severe sympathomimetic agitation, seizures, and alcohol withdrawal.
7. Rapid cooling is essential for toxin-induced hyperthermia.
8. Pregnancy is not a reason to withhold indicated antidotes such as N-acetylcysteine or sodium bicarbonate.
9. Contact poison control or medical toxicology early.
10. Destination must match the expected rescue capability.

References

1. International Board of Specialty Certification. Maternal Fetal Transport Microcredential Candidate Handbook. Updated April 2026.
2. American College of Obstetricians and Gynecologists. Opioid Use and Opioid Use Disorder in Pregnancy.
3. American College of Obstetricians and Gynecologists. Cannabis Use During Pregnancy and Lactation. 2025.
4. American College of Obstetricians and Gynecologists. Alcohol Abuse and Other Substance Use Disorders: Ethical Issues in Obstetric and Gynecologic Practice.
5. American Heart Association. Adult and Pediatric Special Circumstances of Resuscitation: Toxicology. 2025.
6. American Society of Addiction Medicine. Opioid Use Disorder in Pregnancy.
7. America's Poison Centers. Poison Help resources.