DOPAMINE

“INTROPIN”

1) Therapeutic drug action & mechanism(pharmacology)

• Sympathomimetic

• Only catecholamine that is capable (in a dose related fashion) of stimulating all types of adrenergic receptors

• Effects are dose dependent:

i) inotrope [b₁-receptors]

ii) Vasopressor [a-receptors]; effect at higher dosages

iii) Renal vasodilator [dopaminergic-receptors]

iv) Chronotrope [b₁-receptors]

2) Indications

• Ventricular dysfunction

• Vasodilation

• renal dysfunction/oliguria

3) Effects on organs—side effects

4) Toxic effects/ precautions with administration

• Tachycardia, peripheral vasoconstriction, arrythmias

• Avoid extravasation

• Use with caution in hypovolaemic patients

5) Contraindications

• Tachyarrythmias

• Idiopathic hypertrophic subaortic stenosis

• Tetralogy of Fallot with RV outflow tract obstruction (as may constrict pulmonary vasculature exacerbating preexisting pulmonary hypertension or right ventricular dysfunction

6) Reversal, antagonism or antidote

• Short half life

• Antagonist is phentolamine [short acting alpha blocker]

7) Loading dose, maintenance dose, frequency & method of administration

• 1 ampule=400mg/5 ml: add to 100ml D5W

• Continuous infusion into large vein

• Renal effects at: 1-2mg/Kg/min

Beta effects at: 2-5 mg/Kg/min

Alpha effects at: >5 mg/Kg/min

8) Drug’s metabolism—Drug’s excretion—Half life (pharmacokinetics)

• Dopamine is distributed to all tissues except CNS

• Is metabolised in liver by monoamine oxidase

• Excreted by kidneys as metabolites

9) Important drug interactions

• Give with caution to patients on MAO or tricyclics as will prolong action

• Interact with bicarbonate