5 Friends (or 2) Dosages

Question 1

Phenylephrine alternate name:

Answer 1

Neosynephrine

Question 2

Phenylephrine structure:

Answer 2

Synthetic non-catecholamine sympathomimetic

Question 3

Phenylephrine MOA:

Answer 3

1. Alpha 1 stimulation (Gq)
2. Vasoconstriction arterial/venous
3. Stimulation of phospholipase C → hydrolyzes PIP2 to IP3 and DAG which both release intracellular Ca → vasoconstriction

Question 4

Phenylephrine Onset:

Answer 4

Immediate

Question 5

Phenylephrine duration of action:

Answer 5

5-20 min

Question 6

Phenylephrine PB:

Answer 6

95%

Question 7

Phenylephrine Metabolism:

Answer 7

Monamine Oxidase

Question 8

Phenylephrine IV bolus dose:

Answer 8

50-200 mcg

Question 9

Phenylephrine IV infusion dose:

Answer 9

20-200 mcg/min

Question 10

Phenylephrine IV / Kg infusion dose:

Answer 10

0.05-1 mcg/kg/min

Question 11

Phenylephrine side effects:

Answer 11

1. Increased SVR
2. Increased BP
3. Increased ICP
4. Increased CVP
5. *Decreased CO

Question 12

Phenylephrine contraindications / cautions:

Answer 12

1. Reflex Bradycardia
2. Do not give if low HR
3. Do not give to peds (rate dependent)
4. Use with MAOIs can lead to severe hypertensive crisis
5. Pheochromocytoma

Question 13

Ephedrine alternate name:

Answer 13

Corphedra

Question 14

Ephedrine Structure:

Answer 14

Synthetic non-catecholamine sympathomimetic

Question 15

Ephedrine MOA:

Answer 15

1. A1, B1 & B2 stimulation (Gq/Gs) more beta than alpha
2. Directly stimulates A1 & B2 receptors
3. Indirectly taken up by sympathetic nerve endings & displaces noradrenaline from storage in synapse → produces indirect A1 & B1 effects
4. Indirectly inhibits the intraneuronal metabolism of NE by mitochondrial MAO = more NE

Question 16

Ephedrine Onset:

Answer 16

Immediate

Question 17

Ephedrine duration of action:

Answer 17

15-90 min

Question 18

Ephedrine PB:

Answer 18

30%

Question 19

Ephedrine metabolism:

Answer 19

Minimal hepatic, Primarily excreted unchanged Renally

Question 20

Ephedrine IV dose:

Answer 20

5-25 mg

Question 21

Ephedrine side effects:

Answer 21

1. Increase BP
2. Increase HR
3. Increase CO
4. Increased ICP
5. Bronchodilation

Question 22

Ephedrine Contraindications / cautions

Answer 22

1. Can cause MI
2. Not a substitute for adequate fluid management
3. Crosses the placenta
4. Use with MAOIs can lead to severe hypertensive crisis
5. Pheochromocytoma