Drug

Rx

Effect on different systems in the body

Halothane 

(1st series standard)

Not used commonly anymore due to its hepatotoxicity & new drugs on market.

CNS

Fast smooth muscle induction, stage II present.

↑ cerebral blood flow and ↑ intracranial pressure.

Autonomic

Bradycardia (↓Heart Rate)

Cardiovascular system

↓BP, Sensitised myocardium for arrhythmogenic effects of catecholamines.

Halothane will sensitise the heart for catecholamine heart effects, be careful in pts with heart problems.

Respiratory system

No saliva, Bronchial secretions or cough.

Musculo-skeletal system

Skeletal muscle relaxing effects in stadium III

↑ Action of the non-depolarizing muscle relaxants

↓ Action of the depolarizing skeletal muscle relaxants.

Post-operative shaking = lead to hypoxia

Uterus

↓ muscle contractions

Halothane was commonly used to promote the external twisting of the baby. If the baby is not in the correct position in the birth canal then they would turn the baby externally.

Liver

Hepatotoxic (rare & unpredictable).

Be careful in pt’s with liver cirrhosis, and decreased liver functioning.

Enflurane

Used for maintenance.

CNS

Fast, smooth induction convulsions.

CI in elpileptic pts.

Cardiovascular system

No sensitisation of the myocardium.

Less oppressive than Halothane.

Respiratory system

More suppressive than Halothane.

Isoflurane

More ideal drug than Halothane & Enflurane. Widely used.

Has replaced Halothane and Enflurane. 

Not for pts who have to breathe spontaneously/ has respiratory problems.

CNS

Faster induction & recovery than Halothane

Cardiovascular system

Less oppressive than Halothane

No sensitization of myocardium

Respiratory system

MOST POTENT RESPIRATORY DEPRESSOR.

Potent ↓ effect

Skeletal muscle relaxing effects

Desflurane

*Strong irritating smell

It is more ideal than Isoflurane or Sevoflurane.

Potential to be used for various surgical procedures. 

Because of its effect on the respiratory system, NOT used as induction.

CNS

Faster induction & recovery than Isoflurane

↑ Intracranial pressure

↑ cerebral blood flow

Cardiovascular effects

Less suppressive effect than Halothane & Enflurane

Respiratory system

Potent smell

Irritating in airways

If used as inducing agent, it causes a cough, SOB and laryngospasm

Sevoflurane

Induction and maintenance.

Effects similar to Desflurane, less irritation of airways.

Potentiate the effects of the non-depolarising muscle relaxants like the other halogenated ethers.

Undergoes liver metabolism & chemically unstable.

*Caution in pts with reduced/ compromised liver function.

Nitrous Oxide

(N2O)

*Inorganic gas

Used as an additive drug in anesthesia.

Single drug for short dental procedures e.g. extractions.

CNS

Weak anesthetic, potent analgesic, amnesia

Cardiovascular system

No effect

Respiratory system

Pure N2O causes hypoxia. Must always be mixed with O2 or air.

Recovery phase: N2O fast diffusion from the blood to the alveoli and is expired outside, ↓ O2 pressure = hypoxia

No skeletal muscle relaxing effects