Chapter 18 - Adrenergic Drugs

A patient in the intensive care unit has received too high a dose of epinephrine. The nurse will monitor for what effects? What will the nurse expect to do for this patient?

The toxic effects of adrenergic drugs are mainly an extension of their common adverse effects, such as seizures, hypotension or hypertension, dysrhythmias, and other effects, but the two most life-threatening toxic effects involve the central nervous system and cardiovascular system. Seizures can be managed effectively with diazepam. An extreme elevation in blood pressure poses the risk for hemorrhage in the brain and elsewhere in the body. To lower the blood pressure quickly, a rapid-acting beta-adrenergic blocking drug can be used to reverse the adrenergic effects. Most of the adrenergic drugs have very short half-lives; therefore their effects are relatively short-lived. Stopping the drug should quickly cause the toxic symptoms to subside. The treatment of over-doses often focuses on treating the symptoms and supporting the patient's respiratory and cardiac functions.

Adverse Effects:

Unwanted CNS effects of the alpha-adrenergic drugs include headache, restlessness, excitement, insomnia, and euphoria. Possible cardiovascular adverse effects of the alpha-adrenergic drugs include chest pain, vasoconstriction, hypertension, tachycardia, and palpitations or dysrhythmias. Effects on other body systems include anorexia (loss of appetite), dry mouth, nausea, vomiting, and, rarely, taste changes. The beta-adrenergic drugs can adversely stimulate the CNS, causing mild tremors, headache, nervousness, and dizziness, or the cardiovascular system, including increased heart rate (positive chronotropy), palpitations (dysrhythmias), and fluctuations in blood pressure. The toxic effects of adrenergic drugs are an extension of their common adverse effects, such as seizures from excessive CNS stimulation, hypotension or hypertension, dysrhythmias, palpitations, nervousness, dizziness, fatigue, malaise, insomnia, headache, tremor, dry mouth, and nausea. The two most life-threatening effects involve the CNS and cardiovascular system.

Nursing Process:

Use of adrenergic agonists requires careful patient assessment and monitoring to maximize therapeutic effects and minimize possible adverse effects. Focus assessment on a comprehensive health history with past and present medical history, and obtain a past/present medication history. Also include specific system-based questions and identify cautions, contraindications, and drug interactions. Perform a thorough head-to-toe physical assessment and thoroughly assess baseline vital signs, including breath sounds, heart sounds, peripheral pulses, skin color, and capillary refill. There are several nursing interventions that may maximize the therapeutic effects of adrenergic drugs and minimize their adverse effects, such as checking package inserts for the types and amounts of dilutional solutions to use with parenteral dosage forms. When these drugs are given via an inhaler or nebulizer, provide the patient with complete, thorough, and age-appropriate instructions about correct use, storage, and care of equipment. Patients with chronic lung disease who are receiving adrenergic drugs need to avoid anything that may exacerbate their respiratory condition (e.g., food or other allergens, cigarette smoking). If the patient has a chronic respiratory disease, such as emphysema or chronic asthma or bronchitis, it is important for the patient to avoid contact with individuals who may have infections to help minimize situations that would exacerbate the original problem. Respiratory irritants must be avoided. With nasal preparations, rebound nasal congestion or ulcerations of the nasal mucosa may occur if drugs are overused; therefore, educate patients to use these products only as directed. Midodrine use requires careful blood pressure monitoring, so patient education about supine blood pressure measurement and journaling of measured blood pressure values is very important to the effective use of the drug. Myrbetriq, a newer drug for overactive bladder, is associated with dizziness and so encourage the patient to avoid hazardous activities if this occurs. As with any patient with overactive bladder, avoid liquids before bedtime. Inhaled forms of beta2 agonists are used for their bronchodilating action and must be taken only as prescribed, with caution to avoid any overuse of the drug. Overdosage of these drugs may lead to severe cardiovascular, CNS, and cerebrovascular adverse effects and stimulation. Monitor for therapeutic effects of the adrenergic drugs. To evaluate for the occurrence of adverse effects with adrenergic drugs, monitor for stimulation of the systems that are affected, such as the cardiac system and the CNS.

Mr. D., who has had a history of problems with a hormonal imbalance, has been admitted for septic shock, and the physician prescribes dopamine. However, the nurse double-checks the patient's history before administering the drug. What condition may be a contraindication to dopamine?

Use of the drug is contraindicated in patients who have a tumor that secretes catecholamines, such as a pheochromocytoma.

A woman who is allergic to bees has just been stung while out in her garden. She reaches for her bee-sting kit, which would most likely contain which drug? a. Epinephrine b. Phenylephrine c. Formoterol d. Norepinephrine

a

The nurse is aware that adrenergic drugs may be used to treat which conditions? (Select all that apply.) a. Asthma b. Open-angle glaucoma c. Hypertension d. Nasal congestion e. Seizures f. Nausea and vomiting

a, b, d

The nurse is reviewing the medication orders of a newly admitted patient who has an infusion of the adrenergic drug dopamine. Which of these drugs or drug classes, if also given to the patient, may cause an interaction? (Select all that apply.) a. Tricyclic antidepressants b. Monoamine oxidase inhibitors (MAOIs) c. Anticoagulants d. Corticosteroids e. Antihistamines

a, b, e

The nurse is administering dopamine to the patient in cardiogenic shock after a motor vehicle accident. Which assessment finding indicates the dopamine is achieving its desired effect? (Select all that apply.) a. Blood pressure of 90/60 mm Hg b. Hyperactive bowel sounds c. Decreased in heart rate to 100 beats/min d. Presence of adventitious lung sounds e. Increase in urine output to 30 mL/hr

a, c, e

Mr. G. and Mr. C. are both on dopamine infusions. Mr. G.'s infusion is being administered at a low rate, and Mr. C.'s at a high rate. Why might these infusion rates be different?

The action of dopamine depends on the dosage. At low dosages, it can dilate blood vessels in the brain, heart, kidneys, and mesentery, increasing blood flow to these areas. Increased renal flow may help remove excess fluid volume. At higher infusion rates, dopamine can improve contractility and cardiac output.

Anatomy, Physiology, and Pathophysiology Overview:

The body's nervous system is divided into two major branches: the central nervous system (CNS) and the peripheral nervous system. The central nervous system contains the brain and the spinal cord. The peripheral nervous system is subdivided into somatic and autonomic nervous systems, and the autonomic nervous system is further subdivided into the parasympathetic (cholinergic) and the sympathetic (adrenergic) nervous systems. Adrenergic compounds include several exogenous (synthetic) and endogenous (produced in the body naturally) substances. They have a wide variety of therapeutic uses depending on their site of action and their effect on different types of adrenergic receptors. Catecholamines are substances that produce a sympathomimetic response (stimulate the SNS). The naturally occurring or endogenous catecholamines include epinephrine, norepinephrine, and dopamine. An example of an exogenous catecholamine is dobutamine. There are receptor sites for the catecholamines norepinephrine and epinephrine throughout the body referred to as adrenergic receptors. At these receptors, adrenergic drugs bind and produce effects. The beta-adrenergic receptors are all located on postsynaptic effector cells. The beta1-adrenergic receptors are primarily located in the heart, whereas the beta2-adrenergic receptors are located in the smooth muscle fibers of the bronchioles, arterioles, and visceral organs. Another type of adrenergic receptor is the dopaminergic receptor. When stimulated by dopamine (only), these receptors cause the vessels of the renal, mesenteric, coronary, and cerebral arteries to dilate, which increases blood flow to these tissues.

The nurse is to administer epinephrine 0.5 mg subcutaneously. The ampule contains 1 mL of medication and is labeled "Epinephrine 1:1000—1 mg." How many milliliters of epinephrine will the nurse give?

0.5 mL

CASE STUDY: Sixteen-year-old Maureen, who plays soccer on her high school team, has been treated for asthma for 1 year. Her symptoms have been controlled with an inhaled steroid and occasional use of an albuterol metered-dose inhaler. This afternoon, though, her mother brings her into the urgent care center because Maureen has had trouble "getting her breath" after a particularly rough game. Maureen complains of a feeling of "tightness" in her chest and wants to sit up. She appears anxious and has a nonproductive cough. Her respiratory rate is 28 breaths/min, and her peak expiratory flow is 70% of normal. Chest auscultation reveals a short inspiratory period with prolonged expiratory wheezes in both lungs. 1. The physician orders albuterol to be given through a nebulizer. What should you assess before giving this medication? During and after administration? 2. Why is the albuterol given via inhalation rather than orally? 3. After the nebulizer medication treatment is completed, Maureen complains of feeling "shaky and jittery." What do you tell her? 4. The physician gives Maureen a prescription for a salmeterol inhaler. What is important to teach Maureen and her mother about this medication?

1. Before giving this medication, you should assess for hypersensitivity to albuterol and assess breath sounds and vital signs (blood pressure, pulse rate, respiratory rate) to obtain a baseline for comparative purposes. Because this medication may cause tachycardia and cardiac dysrhythmias, the patient's pulse rate and rhythm should be monitored during the treatment. Afterward, you should assess the patient's vital signs and breath sounds again and assess for therapeutic response to the medication. 2. The onset of inhaled albuterol is almost immediate; it would take more time for orally administered albuterol to be absorbed and to become effective. Therefore the inhaled form will take effect faster than the oral form. 3. These are expected side effects of the albuterol and will soon wear off. 4. Salmeterol is indicated for asthma and prevention of bronchospasms in patients who may need long-term maintenance therapy for their asthma. Patients should be taught that salmeterol is not to be used for relief of acute symptoms, and education about its dosing is important. Dosing of salmeterol is usually 1 puff twice daily 12 hours apart for maintenance. For prevention of exercise-induced asthma, the recommendation is 2 puffs 1/2 to 1 hour before exercise and no additional dosing for 12 hours. If Maureen is still taking the inhaled steroid, then the bronchodilator should be taken first, and she should wait approximately 5 minutes before using the steroid inhaler. She will need to rinse her mouth with warm water after taking the inhaled corticosteroid. All equipment should be cleaned regularly.

An infant is having an allergic reaction and is to receive two doses of epinephrine 10 mcg/kg subcutaneously. The infant weighs 11 lb. How many micrograms of medication will the infant receive with each dose?

50 mcg/dose

Mechanism of Action and Drug Effects:

A direct-acting sympathomimetic, such as epinephrine, binds directly to the receptor and causes a physiologic response. An indirect-acting sympathomimetic causes the release of the catecholamine from the storage sites (vesicles) in the nerve endings; it then binds to the receptors and causes a physiologic response. Adrenergic agents can also be classified as either selective or nonselective in their actions, meaning they affect only one receptor subtype. Although adrenergics work primarily at postganglionic receptors peripherally, they may also work more centrally in the nervous system at the preganglionic sympathetic nerve trunks. When beta1-adrenergic receptors, located on the myocardium and in the conduction system of the heart, are stimulated by an adrenergic drug, three things result: 1. An increase in the force of contraction (positive inotropic effect) 2. An increase in heart rate (positive chronotropic effect) and 3. An increase in the conduction of cardiac electrical nerve impulses through the atrioventricular node (positive dromotropic effect) In addition, stimulation of beta1 receptors in the kidney causes an increase in renin secretion. Activation of beta2-adrenergic receptors produces relaxation of the bronchi (bronchodilation) and uterus and also causes increased glycogenolysis (glucose release) from the liver. Epinephrine is available in two strengths for IV use and was historically labeled as a ratio, which led to many medication errors. Starting in May 2016, epinephrine injections are labeled like all other injectable drugs in a mg/ml concentration, as 1 mg/mL or 0.1 mg/mL.

Adrenergic Drugs:

Adrenergics are drugs with effects that are similar to or mimic the effects of the SNS neurotransmitters norepinephrine, epinephrine, and dopamine. They are either endogenous substances such as epinephrine, norepinephrine, and dopamine, or synthetic substances such as dobutamine and phenylephrine. The three endogenous catecholamines are also available in synthetic drug form. Non-catecholamine adrenergic drugs, such as phenylephrine, metaproterenol, and albuterol, are structurally dissimilar to the endogenous catecholamines and have a longer duration of action than either the endogenous or synthetic catecholamines. Epinephrine is available in two strengths for IV use, and was historically labeled as a ratio, which led to many medication errors. It is available as 1 : 1000 (1 mg/mL) and also as 1 : 10,000 (0.1 mg/mL). Starting May 2016, epinephrine injections will no longer be labeled with the ratios, instead will be labeled like all other injectable drugs in a mg/ml concentration, as 1 mg/mL or 0.1 mg/mL.

Indications:

Adrenergics, or sympathomimetics, are used in the treatment of a wide variety of illnesses and conditions. Bronchodilators are drugs that have an affinity for the adrenergic receptors in the respiratory system, preferentially stimulating the beta2-adrenergic receptors and causing bronchodilation. The intranasal application of certain adrenergics can cause the constriction of dilated arterioles and a reduction in nasal blood flow, which thus decreases congestion. Some adrenergics, called ophthalmics, are applied to the surface of the eye. They work in much the same way as nasal decongestants except that they affect the vasculature of the eye. Adrenergics can also be used to reduce intraocular pressure, which makes them useful in the treatment of open-angle glaucoma. They can also dilate the pupils (mydriasis), which makes them useful for diagnostic eye examinations. They produce these effects by stimulating alpha- or beta2-adrenergic receptors, or both. Adrenergic agents are also used to support the cardiovascular system during cardiac failure or shock and are referred to as vasoactive sympathomimetics, vasoconstrictive drugs (known as vasopressive drugs, pressor drugs, or pressors), inotropes, or cardioselective sympathomimetics. Adrenergics that have primarily cardioselective effects are referred to as vasoactive adrenergics and are used to support a failing heart or treat shock or orthostatic hypotension. The beta3 agonist, mirabegron (Myrbetriq), relaxes the detrusor muscle during the storage phase of the bladder fill cycle which leads to an increase in bladder storage capacity. This new mechanism of action is an improvement over other drugs for overactive bladder. Mirabegron should not be used with silodosin, thioridazine, and certain chemotherapeutic agents. It can increase the effects of desipramine, digoxin, aripiprazole, colchicine, and others. It may decrease the effects of metoprolol, tamoxifen, tramadol, and codeine. In 2014, a new oral drug called droxidopa (Northera) was approved for the treatment of neurogenic orthostatic hypotension. Droxidopa is converted to norepinephrine in the body. The most common adverse events are headache, dizziness, nausea, hypertension, and fatigue.

Interactions:

Numerous drug interactions can occur and although many of the interactions result only in a diminished effect because of direct antagonism at and competition for receptor sites, some reactions can be life threatening.

Greg, a 49-year-old construction worker, is in the urgent care center for treatment of a leg laceration. Just after a dose of intravenous penicillin is started, he begins to wheeze and says, "Oh, I just remem-bered. I'm allergic to penicillin!" a. What is happening? b. What will the nurse do first? c. What drug will be given in this situation?

a. He is probably having an anaphylactic reaction to the penicillin. b. First, the nurse must stop the medication! Then she will have someone else notify the physician while she stays with the patient to monitor and support the ABCs (airway, breathing, and circulation). c. Epinephrine is the drug of choice for anaphylactic reactions.

The mother of 3-year-old Kyle is giving him phenylephrine drops as a nasal decongestant. a. How does this medication help with nasal congestion? b. Kyle's mother comes back to the clinic and complains that after 1 week, his congestion is worse, not better. What possible explanation can the nurse offer?

a. The alpha-adrenergic activity of this drug causes vasoconstriction in the nasal mucosa. This pro-duces shrinkage of the mucosa and promotes easier nasal breathing. b. Perhaps she administered the spray too often. Excessive use of nasal decongestants can lead to greater congestion because of a rebound phenomenon.

The nurse is administering an adrenergic drug and will monitor for which possible effect? a. Hypotension b. Tachycardia c. Decreased respiratory rate d. Diarrhea

b

Which instruction should the nurse provide to the patient taking salmeterol by inhaler? a. Increase fluid intake. b. Rinse mouth after use. c. Monitor heart rate. d. Remain upright for 30 minutes.

b

A 13-year-old girl was diagnosed with asthma 2 years ago. Today her physician wants to start her on salmeterol administered via inhaler. The nurse needs to remember to include which statement when teaching the girl and her family about this drug? a. "It should be taken at the first sign of an asthma attack." b. "The dosage is two puffs every 4 hours or any time needed for asthma attacks." c. "This inhaler is for prevention of asthma attacks, not for an acute attack." d. "Be sure to take your steroid inhaler first."

c

During pharmacology class, a nursing student asks about the use of beta2 agonists in pregnancy. The most appropriate response by the nursing faculty member would be which of the following? a. They lower blood pressure in pregnancy-induced hypertension. b. They increase milk production during lactation. c. They interrupt premature labor contractions. d. They facilitate uterine involution.

c

What is another name for an adrenergic drug? a. Anticholinergic drug b. Parasympathetic drug c. Central nervous system drug d. Sympathomimetic drug

d