Thiopental Sodium

THIOPENTAL SODIUM:

• Discovered in 1934

• Powder Form

• Bitter Taste 

• Yellowish

• Garlic like smell  

• Nitrogen is added as preservative 

AVAILABILITY:

• 500mg/20ml=> 2.5% solution

DOSE: 

• 4-7mg/kg
• Healthy young adult: 4mg/kg
• Children : 6mg/kg
• Elder : 2.5-3mg/kg

MECHANISM OF ACTION :

Depress Reticular activating system by depressing GABA receptor.  

PHARMACOKINETIC:

•  Takes less then 30sec to produce effect

ABSORBTION:

• 100% Bioavailability

DISTRIBUTION:

• 75-85% bind with plasma protein albumin

• In 15-25% (61% become unionized)

• Highly lipid soluble

• Easily cross blood brain barrier

BIO TRANSFORMATION: 

• Occurs in Liver

• Follow zero order kinetics

EXCRETION :

• Kidney through unchanged urine  

EFFECT ON CNS:

• Depressing effect cause sleep & amnesia

• Anti convulsant effect => Depress seizures

• Luxury perfusion ( decrease in blood flow no more effect on CMRO2)

• Reversed steef phenomena (increase blood flow in an affected area)

EFFECT ON CVS:

• Heart rate decrease

• Cardiac output decrease

• Vasodilation of peripheral blood vessels

• Cardiac input decrease 

• Cardiac contractility decrease

EFFECT ON RESPIRATORY SYSTEM:

• Depress respiratory centre

• Hypoxia

• Hypercapnia

• Decrease Tidal volume

• Decrease Respiratory Rate

• Branchospasm & Laryngospasm(uncommon)

EFFECT ON RENAL SYSTEM:

• Hypotension 

• Decrease GFR

• Decrease Urine output

EFFECT ON HEPATIC SYSTEM:

• Decrease Hepatic blood flow causes increase drug metabolism

EFFECT ON UTERUS & PLACENTA:
It can cross placenta but don't action on fetus because of the concentration gradient

EFFECT ON EYE:

• IOP decreased to 40%

• Pupil dilate initially

• Decrease blood supply

• Depression of sympathetic system

EFFECT ON SKELETAL SYSTEM:

• Decrease muscle activity

INDICATION :

• Induction

• Spasm

• Use as anti-convulsant

• Treatment of increased ICP

• Cerebral protection (Luxury perfusion & Reverse steef phenomena)

CONTRAINDICATION:

• VHD

• CHF

• Asthma

• Shock

• Shunt

• Endocarditis

• Hypersensitivity reaction

CAUTION:

• Hypertensive

• Hypovolumia

• IHD

• Acute adrenal insufficiency

• Urimeia

• Septicemia

SIDE EFFECTS:

• Hypotension

• Respiratory depression

• Headache

• Restlessness

• Allergic reaction

• Pain on injection (due to crystals)

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