CNS 3 Flashcards
- Were formerly the mainstay of treatment to sedate the patient or to induce and maintain sleep.
- Today, they are largely replaced by the benzodiazepines, primarily because it induce tolerance, drug-metabolizing enzymes, physical dependence, and are associated with very severe withdrawal symptoms. Foremost is their ability to cause coma in toxic doses.
- Certain drugs, such as the very short-acting thiopental, are still used to induce anesthesia.
Barbiturates
- Interaction with GABAA receptors → enhances ____ transmission
- The binding site is distinct from that of the _____.
- Potentiate GABA action on chloride entry into the neuron by prolonging the duration of the ____ channel openings.
- Can block excitatory ____ receptors
- Anesthetic concentrations of pentobarbital also block high-frequency ____ channels.
- All of these molecular actions lead to ____ neuronal activity
- GABAergic
- benzodiazepines
- chloride
- glutamate
- sodium
- decreased
– acts within seconds
– duration of action of about 30 minutes
– used in the intravenous induction of anesthesia
Thiopental
– duration of action greater than a day
– useful in the treatment of seizures
Phenobarbital
– short-acting barbiturates
– effective as sedative and hypnotic (but not antianxiety) agents
Pentobarbital, secobarbital, and amobarbital
Barbiturates suppress the hypoxic and chemoreceptor response to ___, and overdosage is followed by respiratory depression and death.
CO2
– Barbiturates induce ____ microsomal enzymes in the liver. Therefore, chronic barbiturate administration diminishes the action of many drugs that are dependent on this enzyme metabolism to reduce their concentration.
- P450
the ultrashort-acting barbiturates, such as ____, are used intravenously to induce anesthesia.
thiopental
When used as hypnotics, barbiturates suppress _____ more than other stages.
However, most have been replaced by the benzodiazepines.
REM sleep
Is used in long-term management of tonic-clonic seizures, status epilepticus, and eclampsia.
Phenobarbital
Has been regarded as the drug of choice for treatment of young children with
recurrent febrile seizures. However, it can depress cognitive performance in children, and the drug should be used cautiously.
Phenobarbital
– drowsiness, impaired concentration, and mental and physical sluggishness
– the CNS depressant effects of barbiturates synergize with those of ethanol
- drug hangover
- nausea and dizzeness occasionlly
barbiturates
– increase porphyrin synthesis → contraindicated in patients with acute intermittent porphyria.
– Abrupt withdrawal from barbiturates may cause tremors, anxiety, weakness, restlessness, nausea and vomiting, seizures, delirium, and cardiac arrest.
– Withdrawal is much more severe than that associated with opiates and can result in death
- poisoning
barbiturates
- it acts on a subset of the benzodiazepine receptor family, BZ1.
- has no anticonvulsant or muscle-relaxing properties.
- It shows few withdrawal effects, and exhibits minimal rebound insomnia, and little or no tolerance occurs with prolonged use.
- is rapidly absorbed from the gastrointestinal tract, and it has a rapid onset of action and short elimination half-life (about 2 to 3 hours).
Zolpidem
Adverse effects of this include nightmares, agitation, headache, gastrointestinal upset,
dizziness, and daytime drowsiness
Zolpidem
- is very similar to zolpidem in its hypnotic actions, but it causes fewer residual effects on psychomotor and cognitive functions compared to zolpidem or the benzodiazepines.
- This may be due to its rapid elimination, with a half-life that approximately 1 hour.
Zaleplon
- is an oral nonbenzodiazepine hypnotic (also utilizing the BZ1 receptor similar to zolpidem and zaleplon)
- Also used for treating insomnia
- Effective for up to 6 months of use
- Rapidly absorbed (time to peak, 1 hour)
- Adverse events reported with eszopiclone include anxiety, dry mouth, headache, peripheral edema, somnolence, and unpleasant taste.
Eszopiclone
This novel hypnotic drug that activates melatonin receptors in the suprachiasmatic nuclei of the CNS decreases the latency of sleep onset with minimal rebound insomnia or withdrawal symptoms.
• has no direct effects on GABA-ergic neurotransmission in the CNS.
• Unlike conventional hypnotics, it appears to have minimal abuse liability, and it is not a controlled substance.
•The adverse effects of the drug include dizziness, fatigue, and endocrine changes including decreased testosterone and increased prolactin.
Ramelteon