Barbiturates Big Classification

Habit forming

Low therapeutic index

Mechanism of action and drug affects of barbiturates

• Site of action: brainstem (reticular formation)

• By potentiating the action of GABA, nerve impulses traveling in the cerebral cortex are inhibited.

Indication of barbiturates

All barbiturates have the same sedative-­ hypnotic effects but differ in their potency, time to onset of action, and duration of action.

• 1) Ultra short Acting anesthesia = Short procedures, anesthesia induction, control of convulsions, and reduction of intracranial pressure in neurosurgical patients

• 2) Short-acting/intermediate = Sedation and control convulsive conditions

• 3) Intermediate acting: Sedation and control of convulsive conditions

• 4) Long-acting = Seizure

Contraindications of barbiturates

• Allergies, pregnancy, respiratory difficulties, kidney/liver disease

• Caution for elderly = Fall risk

Adverse effects of barbiturates

Drowsiness/restlessness/excitement/respiratory depression, hypertension, cough

• Reduce REM sleep = Agitation, paradoxical restlessness

Barbiturates: Toxicity and Overdose

• Overdose frequently leads to respiratory
  depression and subsequent respiratory arrest.

• Overdose produces CNS depression (sleep to coma and death).

• Can be therapeutic: 

  • Anesthesia induction

  • Uncontrollable seizures: “phenobarbital coma

Barbiturates: Toxicity and Overdose Treatment

• Symptomatic and supportive

• Maintain adequate airway

• Assisted ventilation and oxygen therapy

• Fluids

• Pressor support

• Urine alkalization (raising urine pH) to hasten elimination

Barbiturate Interactions

• Additive effects:

  • Alcohol, antihistamines, benzodiazepines, opioids, tranquilizers

• Inhibited metabolism

  • MAOIs prolong the effects of barbiturates.

• Increased metabolism (enzyme inducers)

  • Reduces anticoagulant response, leading to possible clot formation