Ketamine

Question 1

What is ketamine?

Answer 1

Phencyclidine derivative

Question 2

What forms is ketamine available in?

Answer 2

Colourless solution in glass vial

10/50/100 mg/ml

Racemic mix or as S(+) enantiomer (less delirium)

IV/IM/PO/PR/intrathecal/epidural

Question 3

What are the induction vs analgesic doses of ketamine?

Answer 3

1-2 mg/kg IV

5-10 mg/kg IM

Analgesic -0.2-0.5 mg/kg

Question 4

What are the chemical properties of ketamine?

Answer 4

Water soluble forming acidic solution pH 3.5 - 5.5

Question 5

What is the absorption/distribution of ketamine?

Answer 5

• well absorbed orally and IM
• oral bioavailability 20%
• protein binding 20-50%
• Vd 3L/kg
• t_1/2 2.5hrs

Question 6

What is the metabolism/excretion of ketamine?

Answer 6

• metabolised in the liver by p450 to norketamine (30% potency)
• norketamine metabolised by conjugation to inactive compound
• excreted in urine

Question 7

What are the uses of ketamine?

Answer 7

• induction of anaesthesia especially in refractory asthma due to profound bronchodilator effects
• sedation in ICU/for short procedures
• analgesia in military field
• in neuroaxial blockade to prolong it’s effect
• drug of abuse

Question 8

What is the MOA of ketamine?

Answer 8

• non-competitive antagonist at NMDA receptors
• antagonist at MOP receptor, antagonist at KOP and DOP receptors (no interaction with GABA)

Question 9

What are the CVS effects of ketamine?

Answer 9

• increased noradrenaline and adrenaline release
• tachycardia
• increased CO
• increased BP
• increased cardiac O2 consumption

Question 10

What are the RS side effects of ketamine?

Answer 10

• increased resp rate
• no decreased laryngeal reflex
• airway maintained
• profound bronchodilation

Question 11

What are the CNS effects of ketamine?

Answer 11

• dissociative anaesthesia (ie strong analgesic and light sleep)
• increased cerebral blood flow
• increased ICP
• increased CMRO2
• increased IOP
• amnesia
• emergence phenomena
• delirium, hallucinations
• increased muscle tone

Question 12

What are the GI SEs of ketamine?

Answer 12

• nausea and vomiting
• salivation