THIOPENTONE

“PENTOTHAL “

1) Action

• Ultra short acting barbiturate — hypnotic

2) Mechanism

• Highly lipid soluble, crosses blood-brain barrier producing hypnosis in one circulation time

3) Indications

Induction of anaesthesia

4) Effects on organs—side effects

• Predictable depressant action on respiration & circulation

• Patients recovering from thiopentone have a “hangover”

• Decreases cerebral metabolism, cerebral oxygen utilisation and cerebral blood flow [unlike inhaled anaesthetic- {use in raised ICP}]

5) Toxic effects/ precautions with administration

• Little or no stage of excitement

• Will only produce unconsciousness [hypnosis]

— for analgesia/absence of relaxes use analgesics;

— for muscle relaxation use muscle blockers

6) Contraindications

7) Reversal, antagonism or antidote

8) Loading dose, maintenance dose, frequency & method of administration

• 0.5g/ampoule

• Mix with water for injection

• 500mg per 70 Kg

9) Drug’s metabolism—Drug’s excretion—Half life (pharmacokinetics)

• Short duration of action due to redistribution from brain to muscle & other organs

• Undergoes biotransformation in liver

• Metabolites are excreted by kidneys over 24 hours

• Cessation of action within 10 minutes

• Elimination half life: 11 hr

• % plasma protein bound: 60 - 97