McKenna's Pharmacology for Nursing, 2e

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

Drug therapy across the lifespan

BOX 31.1

Adrenergic blocking agents CHILDREN

(MI). Table 31.1 shows usual indications for each of these agents. Pharmacokinetics These drugs are well absorbed when given orally and are distributed throughout the body when given IV or orally. They are metabolised in the liver and excreted in faeces and urine. The half-life varies with the particular drug and preparation. Contraindications and cautions The non-selective adrenergic blocking agents are contraindicated in individuals with known hypersensi- tivity to any component of the drug to avoid potentially serious hypersensitivity reactions ; with bradycardia or heart blocks, which could be worsened by the slowed heart rate and conduction ; with asthma, which could be exacerbated by the loss of noradrenaline’s effect of bronchodilation ; with shock or heart failure (HF), which could become worse with the loss of the sympathetic more central nervous system (CNS) adverse effects than other adrenergic blockers, and people who have CNS complications already or who develop CNS problems while taking an adrenergic blocker might do better with a different agent. PREGNANCY AND BREASTFEEDING In general, there are no adequate studies about the effects of adrenergic blockers during pregnancy and breastfeeding, and they should be used only in those situations in which the benefit to the mother is greater than the risk to the fetus or neonate. Adrenergic blockers can affect labour, and babies born to mothers taking these drugs may exhibit adverse cardiovascular, respiratory and CNS effects. Many of these drugs were teratogenic in animal studies. Because of a similar risk of adverse reactions on the baby, breastfeeding mothers should find another way to feed the baby if an adrenergic blocking drug is needed. OLDER ADULTS Older people are more likely to experience the adverse effects associated with these drugs—CNS, cardiovascular, GI and respiratory effects. Because older people often also have renal or hepatic impairment, they are more likely to have toxic levels of the drug related to changes in metabolism and excretion.The older person should be started on lower doses of the drugs and should be monitored very closely for potentially serious arrhythmias or blood pressure changes. Bisoprolol is often a drug of choice for older people who require an adrenergic blocker for hypertension because it is not associated with as many problems in the elderly and regular dosing profiles can be used.

Children are at greater risk for complications associated with the use of adrenergic blocking agents, including bradycardia, difficulty breathing and changes in glucose metabolism.The safety and efficacy for use of these drugs has not been established for children younger than 18 years of age. If one of these drugs is used, the dose for these agents needs to be calculated from the child’s body weight and age. It is good practice to have a second person check the dose calculation before administering the drug to avoid potential toxic effects.Two adrenergic blocking agents have established paediatric doses, and they might be the drugs to consider when one is needed: prazosin is used to treat hypertension, and phentolamine, which is used during surgery for phaeochromocytoma. Children should be carefully monitored and supported when these drugs are given. ADULTS Adults being treated with adrenergic blocking agents should be cautioned about the many adverse effects associated with the drugs. People with diabetes need to be re-educated about ways to monitor themselves for hyperglycaemia and hypoglycaemia because the sympathetic reaction (sweating, feeling tense, increased heart rate, rapid breathing) usually alerts people that there is a problem with their glucose levels. People with severe thyroid disease are also at high risk for serious adverse effects when taking these drugs, and if one of them is needed, the person should be monitored very closely. Propranolol and metoprolol are associated with People who use alternative therapies as part of their daily regimen should be cautioned about potential increased adrenergic blocking effects if the following alternative therapies are combined with adrenergic blocking agents: • Ginseng, sage—increased antihypertensive effects (risk of hypotension and increased CNS effects) • Xuan shen, nightshade—slow heart rate (risk of severe bradycardia and reflex arrhythmias) • Celery, coriander, Di huang, fenugreek, goldenseal, Java plum, xuan seng—lower blood glucose (increased risk of severe hypoglycaemia) • Saw palmetto—increased urinary tract complications People who are prescribed an adrenergic blocking drug should be cautioned about the use of herbs, teas and alternative medicines. If a person feels that one of these agents is needed, the healthcare provider should be consulted and appropriate precautions should be taken to ensure that the person is able to achieve the most therapeutic effects with the least adverse effects while taking the drug. Herbal and alternative therapies BOX 31.2