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Chapter 14: Benzodiazepines

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Which of the following is NOT a pharmacologic property of benzodiazepines?

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(A) sedation

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(B) muscle relaxation

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(C) amnesia

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(D) analgesia

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(E) anticonvulsant

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The answer is D. Although there is some experimental evidence regarding benzodiazepines' ability to modify pain transmission in the spinal cord, benzodiazepines are clinically not considered to have analgesic properties. Benzodiazepines have all of the following properties:

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  • Sedation

  • Hypnosis

  • Anxiolysis

  • Amnesia

  • Anticonvulsant

  • Muscle relaxant

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Ref: Miller RD. Miller's Anesthesia. 8th ed. Philadelphia, PA: Elsevier; 2015.

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What is the mechanism of action of midazolam at the GABAA receptor?

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(A) direct activation of the GABAA receptor and increased chloride conductance

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(B) direct activation of the GABAA receptor and increased potassium conductance

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(C) competitive inhibition at the acetylcholine binding site

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(D) allosteric modulation of GABA binding to GABAA receptor

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(E) increased transmembrane sodium conductance

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The answer is D. Midazolam (and other benzodiazepines) act at the benzodiazepine receptor on the GABAA receptor complex. The binding of midazolam results in increased binding affinity of GABA for the GABAA receptor (allosteric modulation). GABAA activation causes influx of chloride ions and hyperpolarization of the cell membrane. Direct activation of the GABAA receptor can occur with barbiturates and etomidate. NMDA receptor activation alters sodium and potassium conductance. Barbiturates such as thiopental are also thought to act as a competitive inhibitors at CNS acetylcholine (and glutamate) receptors.

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Ref: Miller RD. Miller's Anesthesia. 8th ed. Philadelphia, PA: Elsevier; 2015.

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Which of the following benzodiazepines is considered long-lasting?

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(A) midazolam

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(B) lorazepam

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(C) diazepam

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(D) triazolam

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(E) temazepam

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The answer is C. Diazepam is considered long-lasting as its elimination half-life is 20–50 hours. Midazolam and triazolam are short-acting (midazolam elimination half-life = 1.7–2.6 hours). Lorazepam and temazepam are intermediate-acting (lorazepam elimination half-life = 11–22 hours).

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Ref: Miller RD. Miller's Anesthesia. 8th ed. Philadelphia, PA: Elsevier; 2015.

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Why is midazolam prepared in a solution with the pH adjusted to <4?

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