Adrenergic Mechanisms

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• Pharmaceutical Benefits Scheme Therapeutic Goods Administration MIMS Medicines Database

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• Consists of 2 Subtypes Alpha and Beta Adrenaline VS Noradrenaline Receptor subtype subtype 1 favours noradrenaline over adrenaline Receptors subtype subtype 2 favours adrenaline over noradrenaline Receptors subtype subtype 3 does not care at all.

1. Alpha

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   • Normally alpha 1 is constriction of muscles. I.e abdominal
2. Beta

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   •  B1 in kidneys increased in renin B1 in heart, increase heart rate, contractility and conduction velocity. b2: Lungs dilation 
3. CVS

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   • Increased BP and increased in heart rate, conduction velocity and contractility.
4. Respiratory System
5. Eye

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   • Alpha 1: Contraction of radial muscle B2: Relaxation of ciliary muscle.
6. Energy Metabolism

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   • a1b2: Gluconeogenesis and glycogenlysis Pancreas: a2 decrease insulin secretion b2: increase insulin secretion a.b2: Increase glucagon b3: lipolysis, thermogenesis.
7. GI and Renal systems

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   • Upper GI: a1: Sphincter contraction b2: decreased tone and motility Bladded: a1; sphincter contraction b2: detrusor relaxation prostrate: a1 Prostrate contraction.

Nota:

• It also can affect the CNS by reduce the sympathetic output from the brain.

1. Isoprenaline

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   • Beta-non selective: Increase strength and rate of heart contraction a1, relaxes bronchi and skeletal musculature and gi tract b2. Adverse effects include, palpitations, increased HR, headaches and flushing, mild tremors, hypotension. Delivered via IV
2. Dobutamine

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   • Specific and selective Increase strength of heart contraction b1 Adverse effects is increased HR or increased or decreased BP Adminstered via IV or subcutaneous.
3. Ventolin/Terbutaline

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   • B2: Bronchodilation. Side effects included ciliary muscle relaxation Increase in salivary glands secretion Increase in b1 heart if the concentration is high enough. Increase in insulin secretion decrease in tone and motility of the upper GI tract Increased in glycogenlysis and gluconeogenesis Increased in dilation of abdominal blood vessels Relaxes detrusor in bladder. Route of administration: Inhalation limits systemic effects, oral or IV. Decreases MAO metabolism.
4. Phenylephrine

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   • Reduces the buildup of the fluids of nasal mucosa, improving ventilation, drainage and nasal stuffiness Adverse effects include hypertension, tachycardia, arrhythmia CNS stimulation. elderly are more likely to experience adverse effects. It is metabolized by MAO.
5. Clonidine

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   • It acts on the a2 receptor to reduce release of noradrenaline It decreases BP and HR and decrease aqueous humor production. Adverse effects includes dizziness, sedation, orthostatic hypotension, dry mouth, depression, sleep disorders, GI upset, headache, erectile dysfunction, fatigue.

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• It blocks effects by blocking the sensors. For example, normal people has no effects. For the hypertensive patient, who has overly stimulated renin levels, it reduces the blood pressure. It reduces maximal exercise tolerance in normal patients Decreases in glycogen synthase and increases in phosphorylase, and increase lipase activity

1. Hypoglycemia

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   • Inhibits increase in HR and mask the signs of hypoglycaemia Increase likelihood of excercise induced hypoglycemia in diabetic patients.
2. Propranolol

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   • it is non selective, it acts on B1 and b2, it decrease heart rate, suppress renin, reduce cardiac output, oxygenation of myocardium improved. B2 effect is decreased insulin levels, decreased serum FFA conc, increased triglyceride levels, reduce intraocular pressure of the eye by reduce humor production It may also cause Cardiac failure, bradycardia, bronchospasm, hypoglycaemia, cold extremities fatigue.
3. Metoprolol

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   • Decrease in HR, suppress Renin, reduce cardiac output, increased oxygenation of myocardium. Adverse effects include cardiac failure, brady cardia, cold extremeities, hypoglycaemia and brochospasm (those 2 at high dosages), dizziness, headache, dyspoea on exertion. B1 selectivity reduces pulmonary and glucose metabolism side effects.
4. Prazosin

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   • Prostatic Hyperplasia, increased in prostate size and the activation of A1A leads to contraction of muscle. Usage of Prazosin inhibits vasoconstriction causing a decrease of total peripheral resistance, inhibits smooth muscle contraction. Adverse effects include stimulation of A1 receptors.
5. Tamsulosin

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   • Really really selective A1A adrenergic selective antagonist. It inhinits smooth muscle contraction and the binding to the specific receptors results in relaxation of prostate smooth muscle with improvement in urodynamics.