Table of Contents

History:
Stability & preparation:
Pharmacokinetics:
Pharmacodynamics:
Side effects:
Toxic effects:
Contraindications:
Major interactions:

dopamine

see also:

History:

The naturally occurring immediate precursor of noradrenaline;
was once used for cardiogenic shock with renal hypoperfusion;
was once used to counteract renal & mesenteric vasoconstriction with alpha-adrenergic doses adrenaline & noradrenaline;

Stability & preparation:

40mg/ml 5ml; dilute by addition to saline &/or dextrose fluids;

Pharmacokinetics:

Routes of Administration:

Infusion as short T½
central line preferred
Monitor: blood volume; contractility; periph.perfusion;

Distribution:

Does not readily cross BBB → little effect on CNS receptors

Metabolism:

mainly by monoamine oxidase & COMT;

Excretion:

97% in urine as metabolites; inhib. by probenecid; T½ 2min;

Pharmacodynamics:

<2µg/kg/min:

mainly acts on dopamine DA1 receptors:
- ⇒ renal & mesenteric vasodilation
NB. “renal dose” dopamine does not effect clinical outcomes in pts with ARF (Ann Int Med April 2005)

2-5µg/kg/min:

dose-dep. beta (muscle vasodil.) & decr. NA release:
- ⇒ unchanged total periph. resistance
- ⇒ inc. CO; inc. SV; inc. contractility; inc.P initial only;
NB. HR depends on beta1→SAnode, DA2 →decr.NA rel.; vagal & symp.tone;

5-10µg/kg/min:

alpha effects as well (vasoconst.; inc. BP; inc. ven.press.;)

>20µg/kg/min:

mainly alpha → vasoconstriction mainly → resist.inc.;
- ⇒ decr. renal & mesenteric blood flow & decr. urine output;
- ⇒ risk of tachyarrythmias increases;

Bolus in arrest:

2.5mg/kg approx = 45µg/kg adrenaline;

Side effects:

extravasation necrosis → large V; Rx with S/C local phentolamine;
ectopics; tachycardia; anginal pain; hypotension; vasoconstriction;
aberrant conduction; bradycardia; widened QRS; HT; gangrene;
N/V; headache; piloerection; SOB; azotaemia;

Toxic effects:

HT; marked decrease in pulse pressure;

Contraindications:

phaeochromocytoma; hyperthyroidism;
atrial/ventricular arrythmias;
cyclopropane/halthane anaesth;
hypovolaemia (ensure CVP 10-15cm or PWP 14-18mmHg)
care in peripheral vascular disease (PVD or PAD) (diabetes/Raynaud's/arteriosclerosis) or IHD;

Major interactions:

incompatible with alkali & ? as for adrenaline / epinephrine;
MAOI ⇒ reduce starting dose to 1/10th;
alpha-beta blockers, etc. may cause complex interactions;
Probenecid ⇒ decr. excretion;
? butyrophenones ⇒ block renal vasodilatation;