Sympathomimetics Flashcards
Phenylephrine (Neosynephrine)
MOA
&
Receptors
Direct agonist to α1 adrenergic receptors - GCPRs
Primarily only effects venous & arterial vasoconstriction
Indirectly evokes release of NE from postganglionic sympathetic nerve endings
Phenylephrine (Neosynephrine)
Indications
&
CV Effects
Hypotension;
Useful in CAD & aortic stenosis
Intense vasoconstriction (venous/arterial) may cause reflex bradycardia
α1 - ↑↑↑
β1 - N/A
β2 - N/A
CO - ↓
HR - ↓
SVR - ↑↑↑
Phenylephrine (Neosynephrine)
Dosing
IV: 50-100 mcg
Q 1 min
Infusion:
40-200 mcg/min
Typical: 100 mcg/min
Phenylephrine (Neosynephrine)
Onset
Duration
1/2 Time
Onset
Rapid
Duration
1 min
1/2 Time
2.5 hrs
Phenylephrine (Neosynephrine)
Side Effects
&
Considerations
Transient HTN; Reflex bradycardia
No significant prolongation of LAs
Used to counteract SNS depression of
inhaled VA & injected Anesthetics
Preferred sympathomimetic for pregnancy hypotension associated w/ SAB;
no effect on uterine blood flow
Ephedrine (Akovaz & Corphedra)
MOA
&
Receptors
Indirect: Evokes release of NE from postganglionic sympathetic nerve endings Released NE agonizes α1 adrenergic receptors
- GCPRs
Arteriole vasoconstriction & agonizes
β1 receptors which ↑ cAMP production,
↑ intracellular Ca++; enables intense actin/myosin cross bridging
↑ inotropy
α1 effects > β effects;
Ephedrine (Akovaz & Corphedra)
Indications
&
Effects
Hypotension;
Bradycardia;
Bronchoconstriction
BP response less intense than EPI/Neo
however, duration is 10X longer than EPI
Ephedrine DOC if NOT β blocked
α1 - ↑↑
β1 - ↑
β2 - ↑
CO - ↑↑
HR - ↑↑
SVR - ↑
Ephedrine (Akovaz & Corphedra)
Dosing
IV: 5-10 mg;
Tachyphylaxis after 2-3 doses
IM: 50 mg
Ephedrine (Akovaz & Corphedra)
Onset
Duration
1/2 Time
Onset
Rapid
Duration
60 min
1/2 Time
5 hrs
Ephedrine (Akovaz & Corphedra)
Side Effects
&
Considerations
↑HR; transient HTN; does not cause hyperglycemia
Concurrent MAOI use can prolong effects
Agonizes respiratory
β2 adrenergic receptors causes bronchiole smooth muscle dilation/relaxation
No significant prolongation of LAs
Used to counteract SNS depression of inhaled VA & injected anesthetics
No longer preferred sympathomimetic for pregnancy hypotension associated w/ SAB;
can cause fetal acidosis; no effect on uterine blood flow
Vasopressin (ADH & Arginine Vasopressin)
MOA
&
Receptors
AVP binds to V1 receptors on vascular smooth muscle to cause vasoconstriction thru the IP3 signal transduction pathway & Rho-kinase pathway resulting in ↑ arterial pressure
Activates V2 receptors in renal collecting tubule to ↑ H2O reabsorption
Vasopressin (ADH & Arginine Vasopressin)
Indications
&
Effects
Hypotension; Hypovolemia
Especially effective in ACE-I
induced hypotension
α1 - N/A
β1 - N/A
β2 - N/A
V1 - ↑↑
CO - ↑↑
HR - ↓
SVR - ↑↑
Vasopressin (ADH & Arginine Vasopressin)
Dosing
IV: 1-2 units
Infusion:
0.01-0.04 units/min
Vasopressin (ADH & Arginine Vasopressin)
Onset
Duration
1/2 Time
Onset
Rapid; peaks in 15 min
Duration
20 min
1/2 Time
10-20 min
Vasopressin (ADH & Arginine Vasopressin)
Side Effects
&
Considerations
Possible coronary artery vasoconstriction w/ high doses; Stimulates GI smooth muscles; abd pain & N/V; ↓ PLT count & AB formation
Maintenance of hemodynamics;
may ↓ effectiveness of sedation d/t ↑ metabolic activity & CO
Significant prolongation of LAs activity;
Used to counteract SNS depression of
inhaled VA & injected anesthetics