Core pharmacology

Class Group

ADRENERGIC

Legacy Cicm Level

Level 3

Introduction

natural catecholamine released in certain cells in the brain and interneurons of the autonomic ganglia, dopamine is not converted to noradrenaline and is released as a neurotransmitter

Indications Uses

primarily for improving haemodynamic parameters and increasing urine output

Presentation

Inj-clear liquid 40mg/mL in 5 mL vials. CVC only(necrosis). Not with alk solns such as NaHCO3

Main Action

acts centrally as a neurotransmitter and peripherally it has natriuretic and diuretic properties.

Mechanism of action

α, β + dopamine (D1 and D2) receptors via Gs and Gi coupled adenylyl cyclase leading to
increased or decreased levels of cAMP.

1. Low doses (1-5mcg/kg/min) dopamine acts on dopamine receptors. D1 increases cAMP.
2. At moderate doses (5-10mcg/kg/min) acts via direct and indirect stimulation of alpha and beta receptors- beta predominates
3. High doses (>15mcg/kg/min) alpha effects predominate

Physiological effects

1. CVS
- At lower doses it primarily acts on beta1 receptors to increase HR and contractility. Acts indirectly to increase endogenous noradrenaline release.
- At higher doses alpha effects predominate which increases SVR
- Less arrhythmogenic than adrenaline

2. Resp
- Attenuates carotid bulb chemo-R to hypoxia
- Increased PVR

3. GIT
- Vasodilates mesenteric vessels via D1-R
- Increased GIT transit time

4. Renal
- Increased RBF
- Inhibits proximal sodium reabsorption leading to increased UO

5. CNS
- Modulates EPS and inhibits prolactin secretion from pituitary. Cannot cross BBB

6. Miscellaneous
- CTZ stimulation leads to N/V

Adverse Effects Toxicity

Needs adequate fi-lling prior to initiation of therapy. At very high doses it may cause peripheral tissue necrosis due to vasoconstriction. May cause
vomiting CTZ activation. Caution with MAO inhibitors

Absorption

IV. BA 100%. commence @ 2.5 mcg/kg/min-max 60mcg/kg/min onset / dur 5 min/10min

Distribution

does not cross the BBB

Metabolism

Renal, hepatic, plasma by COMT and MAO; 75% to inactive metab and 25% to norad

Excretion

Urine (as metabolites)

Half-life

2 minutes

Route And Dose

IV Infusion
As above