Promethazine

Question 1

Brand Name

Answer 1

Phenergan

Question 2

Broad Category

Answer 2

Antiemetic / Antihistamine / Sedative

Question 3

Pharmacological Class

Answer 3

Phenothiazine derivative
First gen H1-receptor antagonist

Question 4

MOA

Answer 4

H1 Receptor: competetive antagonist

D2 Receptors: receptor antagonist centrally in CTZ

Antimuscarinic activity which treats motion sickness

Alpha-adrenergic blocking properties

Question 5

Uses

Answer 5

N/v
Anxiety
analgesic adjunct (historically d/t potentiation)

Question 6

IV dosing

Answer 6

12.5-25 mg IV (Dilute and give slow

Question 7

Onset

Answer 7

3-5 mins

Question 8

duration

Answer 8

4-6 hours

Question 9

Why must be diluted and given slow?

Answer 9

Extravasation or intra-arterial injection can cause severe, irreversible tissue necrosis and gangrene (often resulting in amputation)

Question 10

CV effects

Answer 10

May cause hypotention due to alpha antagonism

Question 11

CNS effects

Answer 11

Sedation
EPS due to D2 antagonization (Akathisia)
Delirium
confusion
vision changes

Question 12

Contraindications

Answer 12

EPS
Parkinsons
Tardive dyskinesia

Question 13

Drug - Drug interactions?

Answer 13

potentiates sedative effects of benzos and opioids (C-section)

Question 14

Metabolism

Answer 14

Extensive Hepatic
- CYP2D6
- CYP2B6
- CYP2C19

Question 15

Elimination

Answer 15

Renal

Question 16

Vd

Answer 16

Very large
- High lipophilicity
- very extensive tissue distribution

Question 17

Clearance Considerations

Answer 17

Flow limited

Reduced clearance with:
- hepatic disease
- CYP inhibition

Question 18

Protein Binding

Answer 18

High
90-95%