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Barbiturate Poisoning

The Essentials of Forensic Medicine and Toxicology - K.S. Narayana Reddy (36th Edition, 2026)

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Introduction

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Uses

1. Sedative-hypnotics
2. Pre-anesthetic medication
3. Seizure disorders (epilepsy)

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Pharmacokinetics (Route of Absorption, Metabolism, and Excretion)

• Most sedative-hypnotics are administered orally; intravenous mode is reserved for seizure control or induction/maintenance of general anesthesia.
• Long-acting sedative-hypnotics have a plasma half-life of up to 80 hours.
• Most are metabolized to alcohols, phenols, and ketones, excreted in urine.
• Phenobarbitone is excreted ~25% unchanged in urine; the rest is metabolized slowly in the liver.

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Adverse Effects (Therapeutic Use)

1. Residual depression ("hangover" effect)
2. Paradoxical excitement in the elderly
3. Localized hypersensitivity - eyes, lips, subcutaneous tissues
4. Synergy (Synergia) - with ethyl alcohol and antihistaminics (potentiation)
5. Contraindicated in acute/intermittent porphyria - since the end product of barbiturate metabolism (phenol derivatives) worsens porphyria

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Toxic Effects / Clinical Signs of Acute Poisoning

(1) CNS

• Confusion, ataxia, slurred speech, lethargy, headache, nystagmus
• Initial pupil constriction → later dilatation (as coma deepens)
• CNS depression → coma, shock

(2) Respiratory System

• Primary cause of death - respiratory center depression
• Persons with COPD or chronic pulmonary disease are more susceptible
• Slow, shallow breathing → decreased minute volume → terminally Cheyne-Stokes breathing → respiratory arrest

(3) Cardiovascular System (CVS)

• Cardiovascular center depression
• Decreased cardiac output
• Patients with CCF are more susceptible
• Hypotension, cold clammy skin

(4) Hypothermia

• Hypothermia, hypotonia, hypotension, cold clammy skin

(5) Gastrointestinal Tract (GIT)

• Decreased peristalsis in deeply comatose cases - can endanger life

(6) Kidney

• Decreased renal perfusion due to hypotension
• Scanty urination, urinary incontinence

(7) Cutaneous Bullae - Barbiturate Bullae (Barb Bullae) [PATHOGNOMONIC]

• Subcutaneous erythematous or hemorrhagic bullae/blisters
• Commonly seen over: shin, knee, hands, or any pressure area
• Neonatal bullae may appear in newborns of mothers who abused sedative-hypnotics, up to 2 weeks after delivery

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Fatal Dose and Lethal Blood Levels

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Treatment of Acute Barbiturate / Sedative-Hypnotic Poisoning

(1) Stomach Wash (Gastric Lavage)

• Indicated only in conscious patients
• Solution: KMnO4 4% (potassium permanganate) with activated charcoal or tannic acid - leave some quantity in the stomach, then suction
• Magnesium sulphate solution left in the stomach causes purgation and prevents further absorption
• Both are effective up to 24 hours of ingestion

(2) Emesis - CONTRAINDICATED

• Emesis (vomiting) is contraindicated as the gag reflex is depressed - risk of aspiration and asphyxia

(3) Specific Antidotes

• No specific antidote available
• Earlier literature mentioned analeptics (CNS stimulants) as antidotes - no longer recommended

(4) Supportive Treatment

• Maintain airway, cardiac output, adequate urinary excretion
• Antibiotics to prevent secondary infection

(5) Nursing Care

• Proper nursing to prevent bed sores
• Catheterization for urinary management

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Autopsy Findings (Postmortem Appearances)

1. Signs of asphyxia: Congestion, cyanosis, petechial hemorrhages
2. Barbiturate bullae/blisters (characteristic finding)
3. Blood: Dark-blue, deoxygenated, liquid blood
4. Stomach (Fundus): Thickened, granular, and hemorrhagic
5. Brain (in delayed death):
   • Bilateral symmetrical necrosis of globus pallidus and corpus callosum
   • Focal generalized necrosis of cerebral and cerebellar areas

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Laboratory Diagnosis

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Chronic Barbiturate Poisoning

Signs and Symptoms (Similar to Alcohol Intoxication):

1. Physical deterioration:
   • Ataxia, cerebral dysfunction, dysarthria, hypertonia
   • Parkinsonian tremors
2. Social deterioration:
   • Mood, behavior, and intellectual dysfunction
3. Barbiturate Abstinence Syndrome (Withdrawal Syndrome):
   • Physical and psychological dependence - abrupt cessation causes withdrawal
   • Symptoms: visual disturbance, anxiety, dizziness, insomnia, nausea, vomiting, restlessness, tremors, convulsions

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Medico-Legal Importance

1. Suicide: Barbiturates are a well-known drug of suicide, especially among patients on treatment, addicts, and medical professionals with drug knowledge.
2. Drug of Euthanasia: In Switzerland, barbiturates are legally used for oral suicidal consumption by an association called the "Exit Association".
3. Drugs of Abuse (Recreational Use):
   • Amobarbital (Amytal)
   • Pentobarbital (Nembutal)
   • Secobarbital (Seconal)
   • These are known by various street/nick names in the world of addicts.
4. Narcoanalysis (Truth Serum):
   • Sodium Amytal and Sodium Pentothal (thiopental) are used as "truth serum" drugs
   • Metered doses produce desired controlled narcosis
   • This narcoanalysis is also called the "Amytal Interview"
5. Judicial Execution:
   • The following sequential drug combination is used for the death sentence:
     • Sodium thiopental (CNS depression)
     • Pancuronium bromide (respiratory muscle paralysis)
     • Potassium chloride (cardiac arrest)

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Summary Table (Quick Revision)

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