Barbiturates - forensic medicine and toxicology .pptx

Toxicology of barbiturates explained beautifully

1. Barbiturates 151-200

2. Types/ Characteristics: Ultra-Short-Acting Barbiturates : Thiopental , Thiamylal Short-Acting Barbiturates : Secobarbital , Hexobarbital Intermediate-Acting Barbiturates: Pentobarbital , Butabarbital Long-Acting Barbiturates :  Phenobarbital, Primidone

3. Pharmacodynamics : Act on the central nervous system (CNS) by enhancing GABA-mediated inhibitory neurotransmission. Pharmacokinetics : Lipid-soluble, allowing rapid absorption and distribution, Metabolized in the liver. Used in cases of poisoning, overdose, or suicide.

4. Active principle: Barbituric acid   from which all barbiturate derivatives are synthesized, Pharmacologically active barbiturates are  alkylated or substituted derivatives  

5. Absorption: Rapid absorption from the gastrointestinal tract  after oral administration, with onset of action varying from 30 seconds to 1 hour depending on the type. Lipophilicity influences absorption speed , with more lipophilic (fat-soluble) barbiturates being absorbed faster. Peak plasma levels are usually reached within 1-2 hours , facilitating quick therapeutic and potential toxic effects.

6. Elimination: Metabolism primarily occurs in the liver , where barbiturates are broken down into inactive metabolites. Elimination is dose- and duration-dependent , with short-acting barbiturates being eliminated faster than long-acting ones. Renal excretion of unchanged drug and metabolites  occurs, with elimination half-life varying from a few hours to over 100 hours depending on the specific barbiturate.

7. Signs and Symptoms: Central nervous system depression , including drowsiness, dizziness, ataxia, and in severe cases, coma. Respiratory depression and hypotension , which can be life-threatening in overdose situations. Pupillary constriction or dilation, and impaired coordination , along with potential signs of overdose such as vomiting, hypothermia, and cyanosis.

8. Period: Onset of fatal effects typically occurs within 1 to 4 hours  after ingestion, especially in overdose cases. The period of fatality can range from a few hours to over 24 hours , depending on the dose, formulation, and promptness of medical intervention.

9. Treatment: Supportive care is essential Activated charcoal Haemodialysis or forced diuresis

10. Post- moterm appearance: Body may appear flaccid and unresponsive , with possible signs of deep coma prior to death. Lividity (livor mortis)  is usually pronounced and fixed, often showing a bluish discoloration due to blood pooling. Other findings  can include pulmonary congestion, oedema, and sometimes gastrointestinal contents containing the drug, but no specific post-mortem signs are pathognomonic for barbiturate overdose