Changes

 

'''Halothane''' was one of the most widely used inhalation agents in veterinary patients. However, it has now been overtaken by other agents such as [[Isoflurane|isoflurane]]. It is most commonly used to maintain anaesthesia after induction with an [[Injectable Agents|injectable agent]], although it has also been used to induce anaesthesia when injection is not possible e.g. poor intravenous access.  

'''Halothane''' was one of the most widely used inhalation agents in veterinary patients. However, it has now been overtaken by other agents such as [[Isoflurane|isoflurane]]. It is most commonly used to maintain anaesthesia after induction with an [[Injectable Agents|injectable agent]], although it has also been used to induce anaesthesia when injection is not possible e.g. poor intravenous access.  

==Pharmacokinetics==

==Pharmacokinetics==

At room temperature, halothane is a liquid and so requires a [[Vaporisers|vaporiser]] before it reaches the patient. It needs to be stored in a darkened bottle due to ultraviolet degradation. It contains a preservative, Thymol, which can accumulate within the vaporiser The '''blood:gas partition coefficient''' is moderately low meaning that it is relatively insoluble in blood. This results in relatively rapid induction, recovery and depth change. The [[Inhalation agents#General Pharmacokinetics#Minimum Alevolar Concentration|'''MAC''']] for halothane is approximately ''0.9%'', meaning it is highly potent. Halothane undergoes a degree of hepatic metabolism by the cytochrome P450 system found in hepatocytes.  

At room temperature, halothane is a liquid and so requires a [[Vaporisers|vaporiser]] before it reaches the patient. It needs to be stored in a darkened bottle due to ultraviolet degradation. It contains a preservative, Thymol, which can accumulate within the vaporiser The '''blood:gas partition coefficient''' is moderately low meaning that it is relatively insoluble in blood. This results in relatively rapid induction, recovery and depth change. The [[Inhalation Agents#General Pharmacokinetics#Minimum Alveolar Concentration|'''MAC''']] for halothane is approximately ''0.9%'' in dogs and ''1.1%'' in cats, meaning it is highly potent. Halothane undergoes a degree of hepatic metabolism by the cytochrome P450 system found in hepatocytes.

==Adverse Effects==

==Adverse Effects==

*Decreased cardiac output due to myocardial contraction depression.  

*Decreased cardiac output due to myocardial contraction depression.  

*Decreased arterial blood pressure.

*Decreased arterial blood pressure.

*May cause cardiac arrhythmias.

*Sensitizes the myocardium to catecholamines so may cause cardiac arrhythmias.

===Respiratory System===

===Respiratory System===

==Contraindications==

==Contraindications==

Halothane should be avoided in patients with increased ICP, cardiac dysfunction, hepatic disease and susceptibility to malignant hyperthermia.

Halothane should be avoided in patients with increased ICP, cardiac dysfunction, hepatic disease and susceptibility to malignant hyperthermia.