Barbiturates

What effect does increasing the lipid solubility of barbiturates have on the duration of action?

Decreases duration of action.

What are the mechanisms of action of barbiturates?

Gaba receptor agonists, block glutamate binding at AMPA receptors, depress the reticular activating system.

What are the clinical uses of barbiturates?

Anticonvulsants, euthanasia agents, general anesthetics.

Where are barbiturates metabolized?

Liver.

Where are barbiturates excreted?

Kidneys.

What are the expected CNS effects associated with administration of barbiturates?

Decrease cerebral blood flow, decrease cerebral oxygen consumption, decreased intracranial pressure, decreased intraocular pressure.

What are the expected cardiovascular effects associated with administration of barbiturates?

Decreased stroke volume, minimal change in cardiac output.

Under what conditions should barbiturates be used cautiously?

In patients with poor liver function, little body fat, or preexisting illnesses that cause acidosis.

Which barbiturate may precipitate ventricular arrhythmias?

Not specified in the provided notes.

Why should barbiturates be avoided in patients undergoing splenectomy?

Not specified in the provided notes.

Define euthanasia.

Ending the life of an individual animal in a way that minimizes or eliminates pain and distress.

In the US, which barbiturates are approved for euthanasia of dogs?

Pentobarbital-phenytoin products.

What happens to a patient following IV injection of pentobarbital + phenytoin sodium administered for the purpose of euthanasia?

Rapid unconsciousness and simultaneous collapse with rapid progression to deep anesthesia and hypotension.

Is pentobarbital allowed for use in food animals?

No.

How would accidental exposure of a patient to pentobarbital be treated?

Not specified in the provided notes.

What patients are considered at-risk patients for barbiturate use?

Patients with poor liver function, little body fat, or preexisting illnesses that cause acidosis.

Why is it essential that ultra-short acting barbiturates be injected IV?

Can cause tissue necrosis if given outside of the vein.

What are the 3 classifications of barbiturates based on duration of action?

Long-acting, short-acting, ultrashort-acting.

What are the 2 classifications of barbiturates based on the chemical side chain of the barbituric acid molecule?

Oxybarbiturates, thiobarbiturates.

Describe the solubility of thiobarbiturates.

Highly soluble in fat.

Where do thiobarbiturates redistribute after leaving the CNS?

Goes to the fat stores of the body.

Give an example of a long-acting oxybarbiturate.

Phenobarbital.

Give an example of short-acting oxybarbiturate.

Pentobarbital.

Give an example of an ultrashort-acting thiobarbiturate.

Methohexital sodium.

What is the primary indication for phenobarbital use?

Anticonvulsant to prevent epileptic seizures.

What DEA schedule is phenobarbital?

IV.

How is phenobarbital administered?

Orally.

What is the primary indication for pentobarbital use?

Euthanasia agent.

What DEA schedule is pentobarbital?

II.

How is pentobarbital administered?

IV or IP.

Why must thiobarbiturates be administered IV?

To avoid necrosis and tissue sloughing.

Why should thiobarbiturates be used cautiously in thin animals?

Redistributes to fat stores in the body.

What may happen if a thiobarbiturate is administered too rapidly through the IV route?

Apnea.

What may happen if a thiobarbiturate is administered too slowly through the IV route?

CNS excitement.

What adverse side effects may occur with the use of barbiturates?

Excessive CNS depression, paradoxical CNS excitement, severe respiratory depression, cardiovascular depression, tissue perfusion.

What is the main component of most euthanasia agents?

Pentobarbital.

What DEA schedule is pentobarbital alone?

Class II.

What DEA schedule is pentobarbital sodium?

Class III.

What are potential adverse side effects of euthanasia agents?

Muscle twitching, death may be delayed, perivascular irritation.

What type of barbiturate is methohexital sodium?

Ultrasort-acting oxybarbiturate.

How does the potency of methohexital compare to thiopental?

Twice as potent.

What DEA schedule is methohexital?

IV.