CNS Depressants and Muscle Relaxants

Question 1

What is the mechanism of action and drug effect of Benzodiazepines when used as a sedative-hypnotic drug?

Answer 1

Benzodiazepines depress CNS activity by binding to GABA receptors in the brain. GABA is the primary inhibitory neurotransmitter of the brain and serves to modulate CNS activity by inhibiting overstimulation.

Question 2

What are the 7 indications of Benzodiazepines?

Answer 2

1) Sedation and sleep induction
2) Skeletal muscle relaxation
3) Seizure disorders
4) Relief of agitation
5) Anxiety
6) Depression
7) Alcohol withdrawal symptoms

Question 3

What are the two contraindications to the use of Benzodiazepines?

Answer 3

1) Narrow-angle glaucoma

2) Pregancy

Question 4

What are the 6 most common adverse effects associated with Benzodiazepines?

Answer 4

1) Headache
2) Drowsiness
3) Paradoxical excitement or nervousness
4) Dizziness or vertigo
5) Cognitive impairment
6) Lethargy

Question 5

Describe the treatment regimen for a person with Benzodiazepine intoxication.

Answer 5

If ingestion is recent, gastric lavage is generally is the most effective means of gastric decontamination. Activated charcoal and a saline cathartic may be administered after gastric lavage to remove any remaining drug. Flumazenil, a Benzodiazepine antidote, can be used to acutely reverse the sedative effects of Benzodiazapines in cases of excessive oral overdose or IV sedation.

Question 6

What is the antidote for Benzodiazapines? How does it work?

Answer 6

Flumazenil is the antidote for Benzodiazepines and it works by competing with Benzodiazepines for binding at the receptors in the CNS.

Question 7

Name two herbal remedies that interact with Benzodiazepines and lead to further CNS depression.

Answer 7

1) Kava root

2) Valerian root

Question 8

What are the four non-Bezodiazepine drugs used as hypnotics and what are their defining characteristics?

Answer 8

1) Zaleplon(Sonata) - Short acting; has a very short half-life.
2) Zolpidem (Ambien) - The CR dosage form causes somnabulation (sleepwalking).
3) Eszoplicone ( Lunesta) - Designed to provide a full 8 hours of sleep.
4) Ramelteon (Rozerem) - Works as an agonists on the body’s melatonin receptors in the CNS.

Question 9

What are the only two non-Benzodiazepine hypnotics that are FDA approved for longterm use in PTs over 18 years old only?

Answer 9

1) Zolpidem (Ambien)

2) Eszopiclone (Lunesta)

Question 10

Even though there are almost 50 different barbiturates approved for clinical use in the US, why are only a handful in common clinical use today?

Answer 10

1) Barbiturates have a low therapeutic index
2) Barbiturates are habit-forming
3) Benodiazepines have a more favorable safety profile and proven efficacy

Question 11

What is the mechanism of action of Barbiturates?

Answer 11

Barbiturates act as CNS depressants by inhibiting nerve impulse transmission to the cerebral cortex. They do this by potentiating GABA.

Question 12

What are the 4 categories of Bartbiurates and what are their indications?

Answer 12

1) Ultrashort Acting - Anesthesia for short surgical procedures, convulsions, IC pressure in neurosurgical PTs.
2) Short Acting - Sedation/Sleep induction and convulsions.
3) Intermediate Acting - Sedation/Sleep induction and convulsions.
4) Long Acting - Sleep Induction, epileptic seizure prophylaxis.

Question 13

What are the 4 contraindications to the use of Barbiturates?

Answer 13

1) Pregnancy
2) Significant respiratory difficulties
3) Severe liver or kidney disease
4) Porphyria

Question 14

What are the adverse effects of Barbiturates?

Answer 14

1) Enzyme inducing
2) Drowsiness
3) Lethargy
4) Dizziness
5) Hangover
6) Paradoxical restlessness or excitement

Question 15

What is used to remedy a case of barbiturate overdose?

Answer 15

Activated charcoal

Question 16

What is enzyme induction and what class of drugs causes it?

Answer 16

An increase in the activity of the hepatic microsomal cytochrome P-450 enzymes resulting in increased drug metabolism and breakdown. Barbituates as a class are notorious enzyme inducers.

Question 17

What are the mechanism of action of Muscle relaxants?

Answer 17

The majority of muscle relaxants work via their sedative effects on the CNS. Dantrolene is the only MR that has direct effects on skeletal muscles and Baclofen is the only one that is a derivative of GABA.

Question 18

What are the indications of Muscle Relaxants?

Answer 18

1) Muscle spasms

2) Relief of pain associated with trigeminal neuralgia

Question 19

What are the specific indications of Baclofen and Intravenous dantrolene?

Answer 19

1) Baclofen - Hiccups

2) IV Dantrlene - Hypermetabolic muscle spasms caused by hyperthermia

Question 20

What is the only contraindication to the use of muscle relaxants?

Answer 20

Severe renal impairment

Question 21

What are the 6 adverse effects that are usually experienced early in muscle relaxant treatment?

Answer 21

1) Muscle weaknes
2) Dizziness
3) Fatigue
4) Lightheadedness
5) Euphoria
6) Drowsiness

Question 22

Which non-Benzodiazepine drug, used as a hypnotic/sedative, is not associated with CNS depression, does not carry the potential for abuse of dependence and does not lead to withdrawal symptoms when treatment stops?

Answer 22

Ramelteon

Question 23

Which class of drugs, indicated as CNS depressants, are able to cross the placenta and be present in milk and are therefore contraindicated in pregnant and lactating women?

Answer 23

Barbiturates - Can cause respiratory depression in the fetus o r neonate.

Question 24

What is the therapeutic range of phenobarbitol? What is the toxic limit and what symptoms would the patient show if over this limit?

Answer 24

Phenobarbitol Therapeutic Range - 10 to 30 mcg/mL
Toxic Level - greater than 40mcg/mL
Symptoms - Cold and clammy skin and RR < 10 bpm