NORADRENALINE

“NOREPHEDRINE; LEVOPHED”

1) Therapeutic drug action & mechanism(pharmacology)

• Sympathomimetic

• Acts on both a and b₁- receptors but has relatively little effect on b₂-receptors

• Like adrenaline: low dose predominantly beta effect; higher dose alpha

• Causes i) vasoconstriction [a-receptor]

ii) Inotrope [b₁-receptors]

iii) Chronotrope [b₁-receptors]

• Consequently increases systemic BP and coronary artery blood flow

2) Indications

• Beta effects: ventricular dysfunction;shock

• Alpha effects: vasodilation; anaphylaxis

3) Effects on organs—side effects

• May see reflex bradycardias

4) Toxic effects/ precautions with administration

• Should not be given to hypovolaemic patients except in emergencies

• Avoid in patients with peripheral vascular thrombosis (may exacerbate ischaemia)

• May precipitate arrhythmias in irritable heart (eg hypoxia, hypercapnia)

• vasoconstriction (splanchnic, renal)

5) Contraindications

• MI [increased afterload]

• 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

• Very short half life

• If an adverse effect requires immediate reversal use adrenoreceptor antagonist

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

• 1:1000 (1mg/ml) in 2 ml ampoule

• May be made up: 2mg/500 ml

• Continuous infusion of 8—16 mg/min

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

• Parenterally administered adrenaline has a rapid onset and short duration of action

• See adrenaline

9) Important drug interactions

• Bicarbonate, barbiturates

• Should not be mixed in saline alone [water O.K.]

• Risk of arrhythmias with volatile anaesthetics

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