Phenylehrine
Chemical
Direct acting synthetic non-catecholamine with α1 activity
Use
↑SVR
Nasal decongestant
Mydriatic to facilitate retinal exam
Presentation
Clear solution 10mg/mL
Dose
(IV) 50 – 100mcg
(SC/IM) 2 – 5mg
Route
IV, IM, SC
Onset
Immediate
DoA
5 mins
MoA
α1 agonist
α1 → Gq → stimulates Phospholipase C → ↑IP3 & DAG → opens Ca2+ channel
Effects of Ca2+
Smooth m.: VC
Cardiac: weak +ve inotropy
Metabolism: ↑BSL
PD
CVS
↑SVR
Reflex ↓HR
CNS
Mydriasis
Genitourinary
↓uterine artery BF
↓renal a. BF
GI
↑BSL
PK
A
IM/SC takes 15 mins to work
D
M
MAO of liver
E
Products of metabolism & route of elimination not identified
Adverse Effects
- Only metabolised by MAO → C/I with MAOI
- Headache
- Sweating
- Urinary retention
- Tissue necrosis
Everything else
- Favourable cord gas profile → ∴used in obstetrics