Core pharmacology

Class Group

Sedative / Hypnotic

Legacy Cicm Level

Level 2

Introduction

5-ethyl-5`-(1-methylbutyl)-2-thiobarbituric acid and is the sulphur
analogue of pentobarbital

Indications Uses

short-acting barbiturate with sedative, hypnotic,
and anticonvulsant properties

Presentation

pale yellowish-white powder-bitter taste and garlicy odour.
readily dissolves producing alkaline
solution due to S−(strongly basic and attracts H+)
reconstituted stable for ~ 1 week

Mechanism of action

increasing the duration of
GABA-dependent chloride channel opening.

Physiological effects

CNS: depress the sensory cortex, decrease motor activity, alter cerebellar function, and produce drowsiness,
sedation, and hypnosis. In high doses, maximally reduces brain VO2 and anticonvulsant activity

Resp: dose-dependent
Resp depression

Adverse Effects Toxicity

Reflex tachycardia (Due to dose dep CO, SV and TPR)
Dosedep Respiratory depression.  CBF, ICP, and brain VO2. Severe anaphylaxis in 1 in 20000.
May precipitate acute porphyria

Absorption

A: IV
onset / duration I.V.: 30-60 seconds / 5-30 minutes

Distribution

High lipid solubility
pKa 7.6

Protein binding

72-86%

Volume of distribution

~1.6L/kg

Metabolism

Hepatic, primarily to inactive metabolites,
when given as an infusion may develop zero order kinetics
due to enzyme saturation

Excretion

renal, reduce dose by one quarter when CrCl <10

Half-life

half life 3-11.5hrs

Route And Dose

Induction: 3-5mg/kg