PreOperative Medications - Lecture 1/29/24

Question 1

If histamine is released what receptor/receptors do we target with antagonists?

Answer 1

Both the H1 and H2 receptors

Question 2

What drugs induce histamine release?

Answer 2

Morphine
Mivacurium (not available in USA)
Pancuron - in high doses
Protamine (heparin)
Atracurium (Tracrium)

Question 3

What happens when histamine activates H1?

Answer 3

Hyperalgesia & inflammatory pain.

Question 4

What happens when histamine activates H2?

Answer 4

Elevates CAMP (B1-like stimulation)
Increases acid/volume production in stomach

Question 5

What does H1 activate?

Answer 5

Muscarinic, cholinergic, 5-HT3, & Alpha adrenergic receptors

Question 6

What does H2 activate?

Answer 6

5-HT3 and B1

Question 7

What are the signs of H1 & H2 activation by histamine?

Answer 7

Hypotension d/t release of NO
Capillary permeability
Flushing
Prostacyclin release
Tachycardia

Question 8

How does an anti-histamine work? Does it prevent histamine release?

Answer 8

No, works by preventing or limiting the responses to the histamine release. Prevents reactions/effects of histamine on the receptor - has to compete with the inverse agonists.

Question 9

What is Benadryl mainly used for?

Answer 9

Antipruritic

Question 10

What is the E 1/2 time of Benadryl?

Answer 10

7-12 hours

Question 11

What is the Oculo-emetic reflex? What H1 receptor antagonist is used to prevent this reflex? How does the drug prevent the reflex?

Answer 11

The oculo-emetic reflex causes increased nausea and vomiting due to extensive manipulation of extraocular muscles
Prevent with Benadryl
Inhibits the afferent arc of the oculo-emetic reflex.

Question 12

What are the black box warnings for Phenergan? What years did they come out?

Answer 12

2005 - Respiratory arrest in children under 2
2009- Infiltration causing serious necrosis

Question 13

What diseases are H2 antagonists primarily used in?

Answer 13

Duodenal Ulcers
GERD

Question 14

What is the major side effect of H2 antagonist?

Answer 14

Weakend gastric mucosa d/t bacteria b/c stomach not acidic enough to kill off bacteria leading to increased pulmonary infections and candida albicans overgrowth. Usually seen with chronic OTC use.

Question 15

By how much can a H2 antagonist increase serum creatinine? Why does this happen?

Answer 15

Increases by 15% b/c there is competition for tubular secretion

Question 16

Name examples of H2 antagonists

Answer 16

Cimetidine (Tagamet)
Ranitidine (Zantac)
Famotidine (Pecid)

Question 17

Which H2 antagonist STRONGLY inhibits CYP450? What drugs last longer because of this?

Answer 17

Cimetidine
Warfarin, Phenytoin, Lidocaine, TCAs, Propranolol, Nifedipine, Meperidine, Diazepam

Question 18

Name the 2 major adverse effects of Tagamet

Answer 18

Increased levels of prolactin (men develop boobs)
Inhibits dihydrotestosterone binding to androgen receptors causing impotence

Question 19

Which H2 antagonist has a weaker binding to CYP enzymes & no significant interactions with other drugs?

Answer 19

Zantac

Question 20

Which H2 antagonist has no interference with inhibition of other CYP450s, but is the most potent d/t longest E 1/2 time. What is this drug’s E 1/2 time?

Answer 20

Pepcid
E 1/2 time is 2.5-4 hrs; great for longer surgical cases.

Question 21

What is the downside of using Pecid?

Answer 21

Interferes with phosphate absorption

Question 22

What is the dose for Pepcid?

Answer 22

20 mg IV

Question 23

How are H2 antagonists dosed for renal impairment?

Answer 23

1/2 of the normal dose

Question 24

How is Zantac dosed?

Answer 24

50mg diluted to 20mL given over 2 mins

Question 25

What drug's metabolism do PPI's inhibit? How do they block activation of Plavix?

Answer 25

Warfarin Block the enzymes that activate Plavix

Question 26

Which PPI is a prodrug?

Answer 26

Prilosec

Question 27

Where does Prilosec protonate to become the active form?

Answer 27

In parietal cells

Question 28

Can Prilosec cause confusion?

Answer 28

Yes; it crosses the BBB - don't give to patients with neuro issues

Question 29

Which PPI has greater bioavaibility and a longer E 1/2 time than Prilosec?

Answer 29

Protonix

Question 30

What drug do you give for NSAID ulcerations?

Answer 30

Prilosec

Question 31

Name the PPIs mentioned in class

Answer 31

Protonix Prevacid Prilosec Dexilent (newer)

Question 32

What can a Mg+ based antacid cause?

Answer 32

Neurologic and neuromuscular impairment

Question 33

What does a dopamine blocker do?

Answer 33

Stimulates gastric motility (prokinetic). Increases lower esophageal sphincter tone (constricts), stimulates peristalsis, and relaxes pylorus & duodenum sphincter

Question 34

Name the dopamine blockers mentioned in class

Answer 34

Reglan Domperidone (new FDA not approved; can get in Mexico/Canada/Switzerland) Droperidol

Question 35

What is the #1 drug for diabetic gastroparesis?

Answer 35

Reglan

Question 36

What syndrome can Reglan cause? What are the s/s of this syndrome?

Answer 36

Neuroleptic Malignant Syndrome High temp, muscle rigidity, tachycardia, confusion

Question 37

What enzyme do dopamine antagonists decrease

Answer 37

Plasma Cholinesterase- leading to slow metabolism of succs, mivacurium, ester LAs This is a theoretical argument - not significant - still okay to give.

Question 38

What drug is just as effective as 4mg of Zofran but is cheaper?

Answer 38

Droperidol

Question 39

Side effects of Droperidol? What is the black box warning for this drug?

Answer 39

Extrapyramidal symptoms, Neuroleptic Malignant Syndrome, FDA black box warning in 2001 for prolonged QT/torsades with higher doses.

Question 40

What other drugs have the same black box warning as Droperidol?

Answer 40

Phenergan & Zofran

Question 41

List the drug interactions Droperidol has

Answer 41

Amiodarone, diuretics, Sotalol, mineralcocorticoids, CCBs

Question 42

How does Serotonin cause vomiting

Answer 42

It is released from the chromaffin cell of the small intestine and then stimulates the vagal afferent thru the 5HT3 receptors

Question 43

Where are the 5HT3 receptors located?

Answer 43

Everywhere, ubiquitous (we are never getting away from this word). But highly concentrated in the GI tract and brain

Question 44

Name the drugs mentioned in class that are %HT3 antagonists. Do they have an effect on motion sickness/vestibular stimulation?

Answer 44

Zofran Kytril Anzemet No they do not have an effect on motion sickness/vestibular stimulation

Question 45

What drug only works on the 5HT receptors?

Answer 45

Zofran

Question 46

How is Decadron dosed based on surgery length time?

Answer 46

2 hr surgery give with induction 4 hr surgery give halfway through surgery Can redose if needed

Question 47

What is the big side effect of Decadron that you need to tell your patient's about?

Answer 47

Perineal burning/itching

Question 48

What is SABA?

Answer 48

Short Acting Beta Agonist