Metaraminol
Chemical
Synthetic non-catecholamine with direct & indirect sympathomimetic effects but predominant α-adrenoreceptor activity
Use
Hypotension
Presentation
Clear solution 10mg/mL
Dose
0.5 – 1mg bolus or as an infusion 1 – 10mg/hr
Route
IV
Onset
1-2mins
MoA
Indirect: taken up by postganglionic symp. nerve endings
Displaces NA
NA released
Mostly affects α1 adrenoreceptors
α1 → Gq → stimulates Phospholipase C → ↑IP3 & DAG → open Ca2+ channel → VC of smooth m. of vessels
Direct
CVS – ↑SVR
Regional BF – ↓CBF & ↓renal BF
PD
CVS
Increased SBP & DBP, reflex bradycardia, increase CA blood flow
PK
(limited data)
D
Doesn’t cross BBB. 45% PPB
M
Not a MAO/COMT substitute
E
Adverse Effects
Reflex ↓HR
Headache
Dizziness
Tremor
Nausea &vomiting
LV failure