Dopamine
Chemical
An endogenous catecholamine neurotransmitter of CNS & PNS with direct activity at DA, β1 & α1 receptors
Use
Inotrope
Renal protection
Presentation
Clear colourless solution for injection
40mg/mL
Diluted in D5W to avoid catecholamine oxidation in alkaline solution (pH D5W = 4)
Dose
IV infusion of 1 – 20mcg/kg/min
1 – 5 mcg/kg/min → D1 receptors of renal vasculature
5 – 10 mcg/kg/min → β1 receptors
>10 mcg/kg/min → α1 receptors
Route
Central vein
Onset
5 mins
MoA
D1 receptors → GS → activates AC → ↑cAMP → smooth m. relaxation in Renal A.
β1 receptors → GS → activates AC → ↑cAMP → ↑Ca2+
Heart: +ve inotropy, +ve chronotropy, +ve dromotropy
Metabolic: lipolysis, ↑FFA
Renal: ↑renin, ↑AII
β2 receptors → GS → activates AC → ↑cAMP
Heart: ↑Ca2+
Smooth m.: inhibits MLCK
Liver: activates glycogen phosphorelase
PD
CVS
+ve INOTROPY
+ve CHRONOTROPY
+ve DROMOTROPY
↑Renal BF
↑SVR
RESP
Dopamine is an inhibitory NT
At carotid body, may depress hypoxic drive
RENAL
↑Renal perfusion
↑GFR
Diuresis
PK
A
IV central vein
M
By plasma, liver, renal MAO & COMT to homovanillic acid & 3,4, dihydroxyphenylacetic acid
25% dose is converted to NA by adrenergic nerves
E
Metabolites conjugated to glucuronic acid for excretion
Adverse Effects
Dilates cerebral vessels
Oxygen responsiveness of carotid body attenuated
Pulmonary shunting
Arrhythmias
Mucosal ischaemia
Immune suppression
Needs CVC
Emesis → stimulates D2 receptors @ CTZ
Drug Interactions
MAOI
Inactivated by alkaline solutions