Adrenaline (Epinephrine)

Adrenaline: Uses, Dosage and Side Effects

Overview

• Adrenaline exerts its effects via alpha-1, -2 and beta-1 and -2 adrenoreceptors.
• The duration of action of adrenaline is short (2–5 min).
• Adrenaline’s effects change depending on the dose. Low-dose infusions mostly have beta-adrenergic effects (increases in cardiac output, myocardial oxygen consumption, decreased threshold for arrhythmias, peripheral vasodilation, and a decrease in diastolic blood pressure).
• At high doses alpha-1 effects predominate, causing a rise in systemic vascular resistance, diverting blood to the central organs; however, this may improve cardiac output and blood flow.
• Respiratory effects include bronchodilation and an increase in pulmonary vascular resistance. Renal blood flow is moderately decreased.

Uses of Adrenaline (Epinephrine)

• Status asthmaticus, cardiac resuscitation, and mitigating the consequences of histamine release in severe anaphylactoid reactions.
• The ophthalmic preparation is used in open-angle glaucoma.

Dose of Adrenaline (Epinephrine) in Dogs and Cats

Dogs, Cats:

• Cardiopulmonary arrest (CPA):
  10 μg (micrograms)/kg of a 1:1000 solution (1000 μg/ml) given i.v. or intraosseously every 3–5 min.  High dose epinephrine (0.1 mg/kg i.v.) maybe considered after prolonged CPA.
• Bronchoconstriction and anaphylaxis:
  • 10 μg (micrograms)/kg of a 1:1000 solution (1000 μg/ml) i.v. or i.m. The i.v. route is preferred if hypotension accompanies an anaphylactoid reaction.

Side Effects of Adrenaline (Epinephrine) in Dogs and Cats

• Produces arrhythmias including ventricular fibrillation because it increases myocardial oxygen demand.
• Other adverse effects include tachycardia, dry mouth and cold extremities.
• Repeated injections can cause necrosis at the injection site.

Contraindications of Adrenaline (Epinephrine) in Dogs and Cats

• The use of human adrenaline pen injections is not recommended (doses in such pens are usually too small to be effective).
• Do not administer adrenaline directly into the myocardium because of the risk of arrhythmias.

Some Notes:

• Beware of using in animals with diabetes mellitus (monitor blood glucose concentration),
  hypertension or hyperthyroidism.
• Use with caution in hypovolaemic animals.
• Overdosage can be fatal so check dose, particularly in small patients.
• Intracardiac injection is not recommended.
• The effects of adrenaline may be potentiated by antihistamines and thyroxine.
• Propranolol may block the beta effects of adrenaline, thus facilitating an increase in blood pressure.
• When adrenaline is used with drugs that sensitize the myocardium (e.g. halothane, high doses of digoxin) monitor for signs of arrhythmias.
• Hypertension may result if adrenaline is used with oxytocic agents.