ETOMIDATE

ETOMIDATE:

• It was introduced into clinical practice in 1972

• It is the only induction agent having least effect on CVS

PHYSICAL PROPERTIES:

• Soluble in water => acidic in pH

• But unstable in water 

• On physiological pH its soluble in lipid

• Its a clear aqueous solution containing Propophyline glycol (35%) which produce pain on injection

• Emulsion => soyabean oil and triglyceride

• Ph 8.1 of both emulsions

AVAILABILITY:

• 20mg/10ml => 2mg/ml

PHARMACOKINETIC:

ABSORPTION:

• Only IV

• 100% Bioavailability

DISTRIBUTION:

• 75% attached to plasma protein

• Lipid soluble

• Non-ionized

• Rapid distribution

• Fast then propofol and thiopental

BIO TRANSFORMATION:

• Hepatic => Phase 1 reaction

• Extra hepatic=> plasma esterase >hydrolysis

EXCRETION:

• 2% excreted as unchanged urine

• Kidney

• Its metabolites are water soluble

• Repeated dose its plasma metabolites get less accumulated in lipids

• No side effects

MOA:

Etomidate is an imidazole derivative with short-acting sedative, hypnotic, and general anesthetic properties. Etomidate appears to have gamma-aminobutyric acid (GABA) like effects, mediated through GABA-A receptor. The action enhances the inhibitory effect of GABA on the central nervous system by causing chloride channel opening events which leads to membrane hyperpolarization

PHARMACODYNAMICS:

EFFECT ON CNS:

• Sedation cause amnesia

• Onset of action > 20sec

• Duration of action > 2-5min

• Terminal of half life > 2.5-5hrs

• Induction > not smooth

• Convulsions > derilium

• Myoclonical seizures in 40%

• 10% cough and hiccup

• Recovery> not smooth

• Agitation

• Nausea/vomiting

• Mild effect on CBF , CBRO2,ICP 

EFFECT ON CVS :

• Mild effect on CVS

• Myocardial activity > Mild effect

• Mild central depression

• CO maintained or mild decrease

• Coronary circulation well maintained

• Causes bradycardia but if we do intubation tachycardia occurs

RESPIRATORY EFFECT

• No apnea

• Mild effects

EFFECT ON ENDOCRINE SYSTEM:

• Effect on 11 beta hydrolase enzyme

• Inhibition of cortisol

• Decrease metabolism

• Immunosupressant

• Decrease immune reaction

• Effect on 18 beta enzyme 

• Hemolysis of blood due to because etomidate osmolarity is more then blood osmolarity

EFFECT ON RENAL :

• No effects seen

EFFECT ON PREGNANCY:

• Its contraindicated steroids are harmful for fetus

INDICATION:

• Sedation

• Used in shock patient

SIDE EFFECTS:

• Cortisol story

• Emergence phenomena

• Hemolysis

• Pain on injection

CONTRAINDICATION:

• Seizures

• Patient who immunosuppresent

• Causes venous thrombosis due to glycol

REFERENCE:

• Smith & atkinhead book of anesthesiology