Epinephrine (Adrenaline): Uses, Dosage and Side Effects
Overview
Epinephrine (adrenaline) exerts its effects via alpha-1, alpha-2, beta-1, and beta-2 adrenergic receptors. The duration of action is short, typically 2โ5 minutes. Its effects vary depending on the dose:
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- Low-dose infusions: Primarily exhibit beta-adrenergic effects, such as increased cardiac output, myocardial oxygen consumption, decreased arrhythmia threshold, peripheral vasodilation, and a reduction in diastolic blood pressure.
- High-dose infusions: Alpha-1 effects dominate, resulting in an increase in systemic vascular resistance and diversion of blood to central organs. This can improve cardiac output and blood flow.
- Respiratory Effects: Includes bronchodilation and an increase in pulmonary vascular resistance. Renal blood flow is moderately decreased.
Uses of Epinephrine in Dogs, Cats, Horses and All Animals
- Status Asthmaticus: Used in emergencies to alleviate severe asthma symptoms.
- Cardiac Resuscitation: Employed during cardiac arrest to stimulate the heart.
- Anaphylactoid Reactions: Administered to mitigate the effects of histamine release in severe allergic reactions.
- Ophthalmic Use: The ophthalmic preparation is used in the management of open-angle glaucoma to decrease intraocular pressure.
- Other Animals:
- Horses: Used in emergencies such as anaphylaxis, cardiac arrest, and acute asthma.
- Livestock (e.g., cattle, sheep): Sometimes used in emergencies for anaphylactic reactions.
Dose of Epinephrine in Dogs, Cats, Horses and All Animals
Dose of Epinephrine in Dogs and Cats:
- Cardiopulmonary Arrest (CPA): 10 ฮผg (micrograms)/kg of a 1:1000 solution (1000 ฮผg/ml) administered i.v. or intraosseously every 3โ5 minutes. High-dose epinephrine (0.1 mg/kg i.v.) may be considered in cases of prolonged CPA.
- Bronchoconstriction and Anaphylaxis: 10 ฮผg (micrograms)/kg of a 1:1000 solution (1000 ฮผg/ml) i.v. or i.m. The i.v. route is preferred if hypotension accompanies the anaphylactoid reaction.
Dose of Epinephrine in Horses:
Typically administered at 0.01โ0.02 mg/kg i.v. for emergency situations like anaphylaxis or cardiac arrest.
Dose of Epinephrine in Cattle, Sheep and Goats:
Emergency dosages vary but are generally within the range of 0.01โ0.02 mg/kg i.v. or i.m., adjusted based on the severity of the situation and the animalโs size.
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Side Effects of Epinephrine in Dogs, Cats, Horses and All Animals
- Arrhythmias: May cause arrhythmias, including ventricular fibrillation, due to increased myocardial oxygen demand.
- Tachycardia: Can induce rapid heart rates.
- Other Adverse Effects: Include dry mouth, cold extremities, and repeated injections potentially leading to necrosis at the injection site.
- Horses: Use cautiously as it may cause excessive sweating, excitement, and arrhythmias.
- Livestock: May exhibit similar cardiovascular effects as dogs and cats, including increased heart rate and arrhythmias.
Contraindications of Epinephrine in Dogs, Cats, Horses and All Animals
- Human Adrenaline Pen Injections: Not recommended for veterinary use as the doses are often too small to be effective.
- Direct Myocardial Administration: Avoid administering adrenaline directly into the myocardium due to the high risk of inducing arrhythmias.
- In Horses: Use with caution in cases of pre-existing heart conditions or severe hypovolemia.
- In Livestock: Avoid in animals with cardiac abnormalities unless in emergency situations.
Some Notes:
- Diabetes Mellitus: Use with caution and monitor blood glucose levels in diabetic animals.
- Hypertension/Hyperthyroidism: Avoid in animals with hypertension or hyperthyroidism due to the risk of exacerbating these conditions.
- Hypovolemic Animals: Exercise caution as epinephrine can worsen hypovolemia.
- Overdosage: Can be fatal, especially in small animals; dose must be checked meticulously.
- Drug Interactions:
- Antihistamines and Thyroxine: May potentiate the effects of adrenaline.
- Propranolol: May block beta effects of adrenaline, potentially increasing blood pressure.
- Myocardium-sensitizing Drugs: When used with drugs such as halothane or high doses of digoxin, monitor for signs of arrhythmias.
- Oxytocic Agents: Concurrent use may result in hypertension.
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