McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 3 1 Adrenergic blocking antagonists

tolerance (individuals often report that their “get up and go” is gone), hypoglycaemia or hyperglycaemia and liver changes. If these drugs are stopped abruptly after long- term use, there is a risk of angina, MI, hypertension and stroke because the receptor sites become hypersensitive to catecholamines after being blocked by the drugs. Clinically important drug–drug interactions A paradoxical hypertension occurs when beta-blockers are given with clonidine, and an increased rebound hypertension with clonidine withdrawal may also occur. It is best to avoid this combination. A decreased antihypertensive effect occurs when beta-blockers are given with non-steroidal anti- inflammatory drugs (NSAIDs); if this combination is used, the person should be monitored closely and dose adjustment should be made to achieve the desired control of blood pressure. An initial hypertensive episode followed by brady­ cardia may occur if these drugs are given with adrenaline. Peripheral ischaemia may occur if the beta-blockers are taken in combination with ergot alkaloids. When these drugs are given with insulin or other oral hypoglycaemic agents, there is a potential for change in blood glucose levels. The person will also not display the usual signs and symptoms of hypoglycaemia or hyper- glycaemia, which are caused by activation of the SNS. Because these effects are blocked, the person will need Prototype summary: Propranolol Indications: Treatment of hypertension, angina pectoris, idiopathic hypertrophic subaortic stenosis (IHSS), supraventricular tachycardia, tremor; prevention of reinfarction after MI; adjunctive therapy in phaeochromocytoma; prophylaxis of migraine headache; management of situational anxiety. Actions: Competitively blocks beta-adrenergic receptors in the heart and juxtaglomerular apparatus; reduces vascular tone in the CNS. Pharmacokinetics: Route Onset Peak Duration Oral 20–30 mins 60–90 mins 6–12 hours IV Immediate 1 min 4–6 hours T 1/2 : 3 to 5 hours with hepatic metabolism and excretion in the urine. Adverse effects: Allergic reaction, bradycardia, HF, cardiac arrhythmias, cerebrovascular accident, pulmonary oedema, gastric pain, flatulence, impotence, decreased exercise tolerance, bronchospasm.

new indications to alert them to potential problems. If this combination is used, the person should monitor blood glucose levels frequently throughout the day and should be alert to new manifestations indicating glucose imbalance.

Care considerations for people receiving non-selective beta-adrenergic blocking agents

Assessment: History and examination

■ ■ Assess for contraindications or cautions: known allergy to any drug or to any components of the drug to avoid hypersensitivity reactions ; bradycardia or heart blocks, shock or HF, which could be exacerbated by the cardiac-suppressing effects of these drugs ; bronchospasm, COPD or acute asthma, which could worsen with blocking of the sympathetic bronchodilation ; diabetes or hypoglycaemia, which could lead to altered blood glucose levels ; thyrotoxicosis because of adrenergic blocking effects on the thyroid gland ; renal or hepatic dysfunction, which could interfere with the excretion or metabolism of these drugs ; and status of pregnancy and breastfeeding because of the potential effects on the fetus or neonate. ■ ■ Perform a physical assessment to establish baseline data for determining the effectiveness of the drug and the occurrence of any adverse effects. ■ ■ Assess level of orientation and sensory function to evaluate for possible CNS effects. ■ ■ Monitor cardiopulmonary status, including pulse, blood pressure and respiratory rate; auscultate lungs for adventitious breath sounds; obtain an ECG as ordered to evaluate for changes in heart rate or rhythm ; check colour, sensation, and capillary refill of extremities to evaluate for possible peripheral vascular insufficiency. ■ ■ Assess abdomen, including auscultating bowel sounds, to monitor for GI effects. ■ ■ Monitor the results of laboratory tests, such as electrolyte levels, to monitor for risk of arrhythmias , adrenal and hepatic function studies, to determine the need for possible dose adjustment. ■ ■ Refer to the Critical thinking scenario for a full discussion of care for a person who is receiving

beta-adrenergic blocking agents. Implementation with rationale

■ ■ Do not stop these drugs abruptly after chronic therapy, but taper gradually over 2 weeks because long-term use of these drugs can sensitise the