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What is the primary mechanism by which barbiturates exert their CNS depressant effects?
Which of the following is NOT a clinical application of barbiturates?
What is the primary effect of sedative-hypnotic drugs on the central nervous system (CNS)?
What adverse effect is associated with high tolerance levels to barbiturates?
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Which of the following terms describes the phenomenon where a drug's removal evokes unpleasant symptoms?
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What is the primary pharmacokinetic characteristic of most sedative-hypnotic drugs like barbiturates?
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Which type of neurotransmitter is GABA classified as?
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What makes barbiturate withdrawal symptoms particularly dangerous?
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What is the primary mechanism of action by which barbiturates produce their effects?
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Which of the following is NOT classified as a type of sedative-hypnotic drug?
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Study Notes
Sedative-Hypnotic Drugs
- Sedative-hypnotic drugs are a group of drugs that depress the central nervous system (CNS).
- They produce dose-dependent effects, meaning the effects increase with the amount of drug taken.
- Sedatives reduce excitement and calm the person.
- Hypnotics produce sleep resembling normal sleep.
Benzodiazepines
- Benzodiazepines are a major subgroup of sedative-hypnotic drugs.
- Other sedative-hypnotic drugs include barbiturates and miscellaneous agents.
Key Terms
- Addiction: A state where the drug user feels compelled to use the drug and experiences anxiety without it.
- Anesthesia: Loss of consciousness with no response to pain.
- Anxiolytic: A drug that reduces anxiety, a type of sedative.
- Dependence: A state where removing the drug causes unpleasant, potentially life-threatening symptoms, often the opposite of the drug's effects.
- REM Sleep: Phase of sleep with rapid eye movements; most dreaming takes place during REM sleep.
- Tolerance: A decrease in drug effect requiring an increase in dosage to maintain the same response.
Neurotransmitters
-
Excitatory Neurotransmitters: Activate nerve cells.
- Acetylcholine
- Glutamate
-
Inhibitory Neurotransmitters: Inhibit nerve cell activity.
- GABA (Gamma-Aminobutyric Acid)
- Glycine
Barbiturates
- Barbiturates are a class of sedative-hypnotic drugs.
- Different types of barbiturates have varying durations of action:
- Phenobarbital: Long-acting
- Secobarbital: Short-acting
- Thiopental: Ultra-short-acting
Mechanism of Action (Barbiturates)
- Barbiturates depress neuronal activity in the midbrain reticular formation, enhancing and prolonging the inhibitory effects of GABA receptors.
- They bind to multiple isoforms of the GABA A receptor.
- Barbiturates increase the duration of GABA-mediated chloride (Cl-) channel opening (hyperpolarization).
- They may also block the excitatory neurotransmitter glutamic acid and, at high concentrations, sodium channels.
GABA Receptor
- Barbiturates activate GABA receptors.
- Activation of GABA receptors opens chloride channels.
- Increased duration of GABA-gated channel opening leads to hyperpolarization of cells.
- Hyperpolarization of cells results in CNS depression.
Clinical Applications (Barbiturates)
- Anesthesia (Thiopental).
- Insomnia and sedation (Secobarbital).
- Seizure disorders (Phenobarbital).
Pharmacokinetics (Sedative-Hypnotics)
- Most sedative-hypnotic drugs are lipid-soluble and well absorbed from the gastrointestinal tract.
- They distribute well to the brain.
- The CNS effects of thiopental are terminated by rapid redistribution of the drug from the brain to other highly perfused tissues.
- Renal excretion eliminates the drug from the body.
Adverse Effects (Barbiturates)
- Drowsiness, severe respiratory and cardiovascular depression.
- Tolerance: The body needs more of the drug to have the same effect.
- Dependence liability: Higher than benzodiazepines.
- Enzyme induction: Can lead to multiple drug interactions.
- Withdrawal symptoms are more severe than opioid withdrawal and can be fatal (no antidote).
- Contraindicated in pregnancy.
Experimental Methods (Sedative-Hypnotic Drug Effects)
-
Mouse/Rat Experiment:
- Weigh two mice or rats.
- Inject one animal with normal saline (control) and the other with Phenobarbital (50 mg/kg) or Thiopental (30 mg/kg).
- Record the observations and time of occurrence in a table.
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Description
This quiz covers the essential concepts related to sedative-hypnotic drugs, including their effects on the central nervous system. It explores different types of these drugs such as benzodiazepines, their uses, and key terms associated with them like addiction and dependence. Test your knowledge on sedative-hypnotic agents and their implications.
