Pharm Test 3
8. The nurse is evaluating the teaching done with a patient who has a new prescription for transdermal clonidine [Catapres-TTS]. Which statement by the patient indicates understanding of the nurse's teaching? "I will apply the patch to a hairless, intact skin area on my upper arm." "I need to apply the patch before my evening meal." "The patch will not cause any skin reaction." "I will need to apply a new patch once every 3 to 4 days."
"I will apply the patch to a hairless, intact skin area on my upper arm."
3. The nurse is teaching a patient with a history of anaphylaxis how to use an EpiPen. Which statement made by the patient indicates that he understands the proper use of this drug? "I will keep my medication in the refrigerator when I'm not using it." "I should take this medication within 30 minutes of the onset of symptoms." "I must remove my pants before injecting the medication into the leg." "I will jab this medication firmly into my outer thigh if needed."
"I will jab this medication firmly into my outer thigh if needed."
7. The nurse is teaching the patient about atenolol [Tenormin]. Which statement by the patient indicates a correct understanding of the nurse's instruction? "I will need to wait for 6 months and then stop this medication." "One missed dose will not affect my blood pressure." "I may experience occasional chest pain and discomfort." "I will not stop taking this drug without the approval of my healthcare provider."
"I will not stop taking this drug without the approval of my healthcare provider."
6. Which statement made by the patient indicates understanding of teaching related to a new prescription for atenolol [Tenormin]? "I will increase my fluids to prevent constipation." "I will not stop taking this medication abruptly." "I will take the first dose of this medicine at night." "I will wear sunscreen and a hat when I work in the sun."
"I will not stop taking this medication abruptly."
5. Which statement is most appropriate for the nurse to include in the discharge teaching plan for a 30-year-old woman beginning a new prescription of clonidine [Catapres]? "If you stop taking this drug abruptly, your blood pressure might go up very high." "You will need to have your blood drawn regularly to check for anemia." "Take this medication first thing in the morning to reduce nighttime wakefulness." "This medication often is used to manage hypertension during pregnancy."
"If you stop taking this drug abruptly, your blood pressure might go up very high."
7. The nurse is caring for a 60-year-old woman who has been prescribed oxybutynin [Ditropan] for the treatment of overactive bladder (OAB). Which statement by the nurse will be the most helpful to include in the teaching plan? "You may experience a slower heart rate. Call your doctor if it is below 60." "Ditropan is very effective. Most patients experience significant relief." "Sip on water and suck on hard candy to help with the problem of dry mouth." "Antihistamines, such as Benadryl, can help with some of the side effects of Ditropan."
"Sip on water and suck on hard candy to help with the problem of dry mouth."
1. A patient is to be discharged home with a new prescription for prazosin [Minipress]. Which statement is most important for the nurse to include in the teaching plan? "You should increase your intake of fresh fruits and vegetables." "You should move slowly from a sitting to a standing position." "Be sure to wear a Medic Alert bracelet while taking this medication." "Take your first dose of this medication first thing in the morning."
"You should move slowly from a sitting to a standing position."
6. The nurse is caring for a group of patients who are all receiving anticholinergic drugs. In which patient is an anticholinergic drug contraindicated? A 60-year-old woman with an overactive bladder (OAB) A 72-year-old man with glaucoma A 45-year-old woman with peptic ulcer disease (PUD) A 26-year-old man being prepared for surgery today
A 72-year-old man with glaucoma
10. Which statements about the anticholinergic drug scopolamine are true? (Select all that apply.) A side effect is sedation. It is used for motion sickness. A side effect is nausea and vomiting. It is used for preanesthetic sedation. It causes CNS excitation.
A side effect is sedation. It is used for motion sickness. It is used for preanesthetic sedation.
1. A nurse is preparing to give bethanechol [Urecholine]. What is an expected outcome of this drug? A. Nondistended bladder B. Increased heart rate and blood pressure C. Improved pulse oximetry reading D. Relief of cardiac rhythm problems
A. Nondistended bladder
Pharmacokinetics of Epinephrine
Absorption. Epinephrine may be administered topically or by injection. The drug cannot be given orally because epinephrine and other catecholamines undergo destruction by MAO and COMT before reaching the systemic circulation. Following subQ injection, absorption is slow owing to epinephrine-induced local vasoconstriction. Absorption is more rapid following IM injection and is immediate with IV administration. Inactivation. Epinephrine has a short half-life because of two processes: enzymatic inactivation and uptake into adrenergic nerves. The enzymes that inactivate epinephrine and other catecholamines are MAO and COMT. (Burchum 149)
Adrenergic Agonist - Sympathomimetics
Adrenergic agonists produce their effects by activating adrenergic receptors. Since the sympathetic nervous system acts through these same receptors, responses to adrenergic agonists and responses to stimulation of the sympathetic nervous system are very similar. Because of this similarity, adrenergic agonists are often referred to as sympathomimetics. Adrenergic agonists have a broad spectrum of indications, ranging from heart failure to asthma to preterm labor. (Burchum 143) Drugs can activate adrenergic receptors by four basic mechanisms: (1) direct receptor binding, (2) promotion of norepinephrine (NE) release, (3) blockade of NE reuptake, and (4) inhibition of NE inactivation. Note that only the first mechanism is direct. With the other three, receptor activation occurs by an indirect process. Examples of drugs that act by these four mechanisms are presented in Table 17-1. (Burchum 143)
Therapeutic Uses of Bethanechol
Although bethanechol can produce a broad spectrum of pharmacologic effects, the drug is approved only for urinary retention. 117 Urinary Retention. Bethanechol relieves urinary retention by activating muscarinic receptors of the urinary tract. Muscarinic activation relaxes the trigone and sphincter muscles and increases voiding pressure (by contracting the detrusor muscle, which composes the bladder wall). Bethanechol is used to treat urinary retention in postoperative and postpartum patients. The drug should not be used to treat urinary retention caused by physical obstruction of the urinary tract because increased pressure in the tract in the presence of blockage could cause injury. When patients are treated with bethanechol, a bedpan or urinal should be readily available. Investigational GI Uses. Bethanechol has been used on an investigational basis to treat gastroesophageal reflux. Benefits may result from increased esophageal motility and increased pressure in the lower esophageal sphincter. Bethanechol can help treat disorders associated with GI paralysis. Benefits derive from increased tone and motility of GI smooth muscle. Specific applications are adynamic ileus, gastric atony, and postoperative abdominal distention. Bethanechol should not be given if physical obstruction of the GI tract is present because, in the presence of blockage, increased propulsive contractions might result in damage to the intestinal wall. (Burchum 116-117)
Safety Alert - BEERS Criteria for Anticholinergics
Anticholinergic drugs have been designated as potentially inappropriate for use in geriatric patients (Burchum 118)
Common anticholinergic side effects for oxybutynin
Anticholinergic side effects are common. The incidence of dry mouth is very high, in part because of muscarinic blockade by oxybutynin itself, and in part because of blockade by N-desethyloxybutynin. Other common side effects include constipation, tachycardia, urinary hesitancy, urinary retention, mydriasis, blurred vision, and dry eyes. In the CNS, cholinergic blockade can result in confusion, hallucinations, insomnia, and nervousness. In postmarketing reports of CNS effects, hallucinations and agitation were prominent among reports involving pediatric patients, while hallucinations, confusion, and sedation were prominent among reports involving older-adult patients. Combined use of oxybutynin with other anticholinergic agents (eg, antihistamines, tricyclic antidepressants, phenothiazine antipsychotics) can intensify all anticholinergic side effects. 123 (Burchum 122-123)
MOA for Competitive (Nondepolarizing) NMBA -
As their name implies, the competitive neuromuscular blockers compete with acetylcholine for binding to nicotinicM receptors on the motor end-plate (Fig. 16-4). However, unlike acetylcholine, these drugs do not cause receptor activation. When they bind to nicotinicM receptors, they block receptor activation by acetylcholine, causing the muscle to relax. Muscle relaxation persists as long as the amount of competitive neuromuscular blocker at the neuromuscular junction is sufficient to prevent receptor occupation by acetylcholine. Muscle function can be restored by eliminating the drug from the body or by increasing the amount of acetylcholine at the neuromuscular junction. (Burchum 136)
9. The nurse is preparing to administer diltiazem and atenolol. What is the priority nursing intervention before administering these two medications to the patient? Obtain blood glucose Observe for lower leg edema Assess the heart rate Apply a pulse oximeter
Assess the heart rate
5. The nurse is preparing to give epinephrine by the IV push route. Which actions are essential before giving this drug? (Select all that apply.) Check the blood urea nitrogen (BUN) and creatinine levels. Obtain insulin from the medication cart. Assess the patency of the IV line. Review the allergy history. Assess the vital signs.
Assess the patency of the IV line. Review the allergy history. Assess the vital signs.
5. The nurse is caring for a patient with myasthenia gravis who is beginning a new prescription of neostigmine [Prostigmin], 75 mg PO twice daily. What is the most important initial nursing action? Obtain a measurement of the plasma level of neostigmine. Teach the patient to wear a Medic Alert bracelet. Assess the patient's ability to swallow. Check the patient's deep tendon reflexes (DTRs).
Assess the patient's ability to swallow.
6. The nurse prepares to administer the antidote to a patient in cholinergic crisis. What medication does the nurse anticipate the healthcare provider to order? Neostigmine [Prostigmin] Atropine Pralidoxime [DuoDote] Dobutamine [Dobutrex]
Atropine
Therapeutic Uses of Atropine - Bradycardia
Atropine can accelerate heart rate in certain patients with bradycardia. Heart rate is increased because blockade of cardiac muscarinic receptors reverses parasympathetic slowing of the heart. (Burchum 119)
Mechanism of Action for Muscarinic Antagonist - Atropine
Atropine produces its effects through competitive blockade at muscarinic receptors. Like all other receptor antagonists, atropine has no direct effects of its own. Rather, all responses to atropine result from preventing receptor activation by endogenous acetylcholine (or by drugs that act as muscarinic agonists). At therapeutic doses, atropine produces selective blockade of muscarinic cholinergic receptors. However, if the dosage is sufficiently high, the drug will produce some blockade of nicotinic receptors too. (Burchum 119)
Mechanism of Action for Muscarinic Agonist - Bethanechol
Bethanechol is a direct-acting muscarinic agonist. The drug binds reversibly to muscarinic cholinergic receptors to cause activation. At therapeutic doses, bethanechol acts selectively at muscarinic receptors, having little or no effect on nicotinic receptors, either in ganglia or in skeletal muscle. (Burchum 116)
Adverse Effects of Prazosin
Blockade of alpha1 receptors can cause orthostatic hypotension, reflex tachycardia, and nasal congestion. The most serious of these is hypotension. Patients should be educated about the symptoms of orthostatic hypotension and be advised to sit or lie down if they occur. Also, patients should be informed that orthostatic hypotension can be minimized by moving slowly when changing from a supine or sitting position to an upright position. About 1% of patients lose consciousness 30 to 60 minutes after receiving their initial prazosin dose. This "first-dose" effect is the result of severe postural hypotension. To minimize the first-dose effect, the initial dose should be small (1 mg or less). Subsequent doses can be gradually increased with little risk of fainting. Patients who are starting treatment should be forewarned about the first-dose effect and advised to avoid driving and other hazardous activities for 12 to 24 hours. Administering the initial dose immediately before going to bed eliminates the risk of a first-dose effect. (Burchum 158)
1. The nurse is monitoring a patient prescribed reserpine for the treatment of hypertension. Which assessment parameter indicates that this medication is effective? Decrease in diarrhea Blood pressure of 118/72 mm Hg Absence of bladder distention Improved symptoms of depression
Blood pressure of 118/72 mm Hg
3. Which symptom is the most indicative of muscarinic poisoning? Constipation Heart rate of 140 beats per minute Blood pressure of 180/110 mm Hg Blurred vision
Blurred vision
2. The nurse in the cardiac care unit is caring for a patient receiving epinephrine. Which assessment criterion takes priority in the monitoring for adverse effects of this drug? Cardiac rhythm Blood urea nitrogen Central nervous system (CNS) tremor Lung sounds
Cardiac rhythm
Safety Alert - Acute Toxicity - Cholinergic Crisis
Cholinesterase inhibitor toxicity can cause a life-threatening cholinergic crisis. Some common mnemonics can help you to identify these potentially dangerous conditions. • Mnemonic 1: SLUDGE and the Killer Bs: S alivation, L acrimation, U rination, D iaphoresis/D iarrhea, G astrointestinal cramping, E mesis; B radycardia, B ronchospasm, B ronchorrhea • Mnemonic #2: DUMBELS: D iaphoresis/D iarrhea; U rination; M iosis; B radycardia, B ronchospasm, B ronchorrhea; E mesis (vomiting); L acrimation (tears); S alivation (Burchum 129)
9. A patient who abuses cocaine, opioids, and other drugs frequently abuses which drug? Guanfacine Reserpine Methyldopa Clonidine
Clonidine
MOA and therapeutic uses for Clonidine
Clonidine has three approved applications: treatment of hypertension (its main use), relief of severe pain, and management of ADHD. Investigational uses include managing opioid withdrawal, facilitating smoking cessation, and treating Tourette's syndrome, a CNS disease characterized by uncontrollable tics and verbal outbursts that are frequently obscene. (Burchum 169)
Neuromuscular Blocking Agents (NMBA)
Competitive neuromuscular blocking agents are drugs that compete with acetylcholine for binding to nicotinicM receptors. These drugs are also known as nondepolarizing neuromuscular blockers, because, unlike depolarizing neuromuscular blockers, they do not depolarize the motor end-plate. The powers of tubocurarine, the oldest competitive neuromuscular blocker, were known to primitive hunters long before coming to the attention of modern scientists. Tubocurarine is one of several active principles found in curare, an arrow poison used for hunting by South American Indians. When shot into a small animal, curare-tipped arrows cause relaxation (paralysis) of skeletal muscles. Death results from paralyzing the muscles of respiration. The clinical utility of the neuromuscular blockers is based on the same action that is useful in hunting: production of skeletal muscle relaxation. Relaxation of skeletal muscles is helpful in patients undergoing surgery, endotracheal intubation, mechanical ventilation, and other procedures. (Burchum 136)
2. A nurse prepares to administer a new prescription for bethanechol [Urecholine]. Which information in the patient's history should prompt the nurse to consult with the prescriber before giving the drug? A. Constipation B. Hypertension C. Psoriasis D. Asthma
D. Asthma
4. The nurse is caring for several patients prescribed propranolol [Inderal]. In which patient condition is propranolol [Inderal] contraindicated? Cardiac dysrhythmias Hypertension Diabetes Angina
Diabetes
3. The nurse is assessing a patient in a clinic who has been taking clonidine [Catapres] for hypertension. Which clinical findings are most indicative of an adverse effect of this drug? Cough and wheezing Epigastric pain and diarrhea Drowsiness and dry mouth Positive Coombs' test result and anemia
Drowsiness and dry mouth
8. The provider elects to administer a medication to distinguish myasthenic crisis from cholinergic crisis. What medication would the nurse anticipate giving? Neostigmine [Prostigmin] Edrophonium Pralidoxime [DuoDote] Dobutamine [Dobutrex]
Edrophonium
Therapeutic Uses of Epinephrine - Adrenergic Agonist
Epinephrine can activate all four subtypes of adrenergic receptors. As a consequence, the drug can produce a broad spectrum of beneficial sympathomimetic effects: • Because it can cause alpha1-mediated vasoconstriction, epinephrine is used to (1) delay absorption of local anesthetics, (2) control superficial bleeding, and (3) elevate blood pressure. In the past, epinephrine-induced vasoconstriction was also used for nasal decongestion. • Because it can activate beta1 receptors, epinephrine may be used to (1) overcome AV heart block and (2) restore cardiac function in patients in cardiac arrest experiencing ventricular fibrillation, pulseless ventricular tachycardia, pulseless electrical activity, or asystole. • Activation of beta2 receptors in the lung promotes bronchodilation, which can be useful in patients with asthma (although other drugs are preferred). • Because it can activate a combination of alpha and beta receptors, epinephrine is the treatment of choice for anaphylactic shock. (Burchum 149)
9. Overdose of cholinesterase inhibitors causes which of the following? (Select all that apply.) Xerostomia Excessive muscarinic stimulation Constipation Respiratory depression Cholinergic crisis
Excessive muscarinic stimulation Respiratory depression (hypoventilation) Cholinergic crisis
10. Prior to discharge, the nurse provides teaching related to adverse effects of terazosin [Hytrin] to the patient and caregivers. Which adverse effects should the nurse include in the teaching of this drug? (Select all that apply.) Headache Hypoglycemia Nasal congestion Erectile dysfunction Orthostatic hypotension
Headache Nasal congestion Erectile dysfunction Orthostatic hypotension
4. The nurse is caring for a patient prescribed methyldopa [Aldomet]. Which laboratory test is most important to obtain before treatment? Creatinine level Serum glucose level White blood cell count Hematocrit
Hematocrit
Adverse Effects of Bethanechol - Contraindications
Hypotension and Heart Failure (low cardiac output) Urinary tract obstruction Weakness of bladder wall Intestinal obstruction Recent bowel surgery Latent or Active Asthma Hyperthyroidism Cardiovascular System. Bethanechol can cause hypotension (secondary to vasodilation) and bradycardia. Accordingly, the drug is contraindicated for patients with low blood pressure or low cardiac output. Gastrointestinal System. At usual therapeutic doses, bethanechol can cause excessive salivation, increased secretion of gastric acid, abdominal cramps, and diarrhea. Higher doses can cause involuntary defecation. Bethanechol is contraindicated in patients with gastric ulcers because stimulation of acid secretion could intensify gastric erosion, causing bleeding and possibly perforation. The drug is also contraindicated for patients with intestinal obstruction and for those recovering from recent surgery of the bowel. In both cases, the ability of bethanechol to increase the tone and motility of intestinal smooth muscle could result in rupture of the bowel wall. Urinary Tract. Because of its ability to contract the bladder detrusor, and thereby increase pressure within the urinary tract, bethanechol can be hazardous to patients with urinary tract obstruction or weakness of the bladder wall. In both groups, elevation of pressure within the urinary tract could rupture the bladder. Accordingly, bethanechol is contraindicated for patients with either disorder. Exacerbation of Asthma. By activating muscarinic receptors in the lungs, bethanechol can cause bronchoconstriction. Accordingly, the drug is contraindicated for patients with latent or active asthma. Dysrhythmias in Hyperthyroid Patients. Bethanechol can cause dysrhythmias in hyperthyroid patients, so it is contraindicated for people with this condition. The mechanism of dysrhythmia induction is explained below. (Burchum 117)
7. What is the pathophysiology for a myasthenic crisis? Insufficient ACh at the NMJ Excessive ACh at the NMJ Overdose with a cholinesterase inhibitor None of the above
Insufficient ACh at the NMJ
Treatment for toxicity of reversible cholinesterase inhibitors
Intravenous atropine can alleviate the muscarinic effects of cholinesterase inhibition. Respiratory depression from cholinesterase inhibitors cannot be managed with drugs. Rather, treatment consists of mechanical ventilation with oxygen. Suctioning may be necessary if atropine fails to suppress bronchial secretions. (Burchum 129)
1. The nurse is reviewing drugs on the emergency cart with regard to their therapeutic action. Which medications can help initiate heart contraction during a cardiac arrest? Topical phenylephrine Subcutaneous terbutaline Intravenous epinephrine Inhaled albuterol
Intravenous epinephrine
2. What best describes the rationale for using neostigmine [Prostigmin] in the treatment of myasthenia gravis? It promotes neuromuscular blockade in the periphery. It promotes emptying of the bladder and sphincter relaxation. It reduces intraocular pressure and protects the optic nerve. It increases the force of skeletal muscle contraction.
It increases the force of skeletal muscle contraction.
10. Which of the following statements about Pralidoxime are true? (Select all that apply.) It is an antidote to organophosphate poisoning. It is an antidote to reversible cholinesterase inhibitors. It cannot cross the blood-brain barrier. It reverses cholinesterase inhibition in the CNS. Doses should be infused slowly.
It is an antidote to organophosphate poisoning. It cannot cross the blood-brain barrier. Doses should be infused slowly.
1. The nurse is preparing to give neostigmine [Prostigmin]. What best describes the action of this drug? It inhibits acetylcholine at all cholinergic synapses. It prevents inactivation of acetylcholine. It prevents activation of muscarinic receptors. It stimulates activation of adrenergic receptors.
It prevents inactivation of acetylcholine.
2. The nurse is preparing to administer a dose of clonidine [Catapres]. Which is the best description of the action of this drug? It selectively activates alpha2 receptors in the central nervous system (CNS). It causes peripheral activation of alpha1 and alpha2 receptors. It depletes sympathetic neurons of norepinephrine. It directly blocks alpha and beta receptors in the periphery.
It selectively activates alpha2 receptors in the central nervous system (CNS).
Adverse Effect of Succinylcholine - Malignant Hyperthermia
Malignant hyperthermia is a rare and potentially fatal condition that can be triggered by succinylcholine. The condition is characterized by muscle rigidity associated with a profound elevation of body temperature—sometimes as high as 43°C. Temperature becomes elevated owing to excessive and uncontrolled metabolic activity in muscle, secondary to increased release of calcium from the SR. Other manifestations include cardiac dysrhythmias, unstable blood pressure, electrolyte derangements, and metabolic acidosis. Left untreated, the condition can rapidly prove fatal. Malignant hyperthermia is a genetically determined reaction that has an incidence of about 1 in 25,000. Individuals with a family history of the reaction should not receive succinylcholine. Treatment of malignant hyperthermia includes (1) immediate discontinuation of succinylcholine, (2) cooling the patient with external ice packs and IV infusion of cold saline, and (3) administering IV dantrolene, a drug that stops heat generation by acting directly on skeletal muscle to reduce its metabolic activity. The pharmacology of dantrolene is discussed in Chapter 25. (Burchum 139)
Treatment for Muscarinic Poisoning
Management is direct and specific: administer atropine (a selective muscarinic blocking agent) and provide supportive therapy. By blocking access of muscarinic agonists to their receptors, atropine can reverse most signs of toxicity. (Burchum 118)
Therapeutic Uses for neostigmine - Two Uses
Myasthenia Gravis. Myasthenia gravis is a major indication for neostigmine and several other reversible cholinesterase inhibitors. Treatment of myasthenia gravis is discussed separately later. Reversal of Competitive (Nondepolarizing) Neuromuscular Blockade. By causing accumulation of acetylcholine at the NMJ, cholinesterase inhibitors can reverse the effects of competitive neuromuscular blocking agents (eg, pancuronium). This ability has two clinical applications: (1) reversal of neuromuscular blockade in postoperative patients and (2) treatment of overdose with a competitive neuromuscular blocker. When neostigmine is used to treat neuromuscular blocker overdose, artificial respiration must be maintained until muscle function has fully recovered. At the doses employed to reverse neuromuscular blockade, neostigmine is likely to elicit substantial muscarinic responses. If necessary, these can be reduced with atropine. It is important to note that cholinesterase inhibitors cannot be employed to counteract the effects of succinylcholine, a depolarizing neuromuscular blocker. (Burchum 128)
Cholinesterase Inhibitors for Myasthenia Gravis
Myasthenia gravis (MG) is a neuromuscular disorder characterized by fluctuating muscle weakness and a predisposition to rapid fatigue. Common symptoms include ptosis (drooping eyelids), difficulty swallowing, and weakness of skeletal muscles. Patients with severe MG may have difficulty breathing owing to weakness of the muscles of respiration. Symptoms of MG result from an autoimmune process in which the patient's immune system produces antibodies that attack nicotinicM receptors on skeletal muscle. As a result, the number of functional receptors at the NMJ is reduced by 70% to 90%, causing muscle weakness. (Burchum 131) Beneficial Effects. Reversible cholinesterase inhibitors (eg, neostigmine) are the mainstay of therapy. By preventing acetylcholine inactivation, anticholinesterase agents can intensify the effects of acetylcholine released from motor neurons, increasing muscle strength. Cholinesterase inhibitors do not cure MG. Rather, they only produce symptomatic relief, so patients usually need therapy lifelong. When working with a hospitalized patient with MG, keep in mind that muscle strength may be insufficient to permit swallowing. Accordingly, you should assess the ability to swallow before giving oral medications. Assessment is accomplished by giving the patient a few sips of water. If the patient is unable to swallow the water, parenteral medication must be substituted for oral medication. Side Effects. Because cholinesterase inhibitors can inhibit acetylcholinesterase at any location, these drugs will cause acetylcholine to accumulate at muscarinic junctions as well as at NMJs. If muscarinic responses are excessive, atropine may be given to suppress them. However, atropine should not be employed routinely because the drug can mask the early signs (eg, excessive salivation) of overdose with anticholinesterase agents. Dosage Adjustment. In the treatment of MG, establishing an optimal dosage for cholinesterase inhibitors can be a challenge. Dosage determination is accomplished by administering a small initial dose followed by additional small doses until an optimal level of muscle function has been achieved. Important signs of improvement include increased ease of swallowing and increased ability to raise the eyelids. You can help establish a correct dosage by keeping records of (1) times of drug administration, (2) times at which fatigue occurs, (3) the state of muscle strength before and after drug administration, and (4) signs of excessive muscarinic stimulation. To maintain optimal responses, patients must occasionally modify dosage themselves. To do this, they must be taught to recognize signs of undermedication (ptosis, difficulty in swallowing) and signs of overmedication (excessive salivation and other muscarinic responses). Patients may also need to modify dosage in anticipation of exertion. For example, they may find it necessary to take supplementary medication 30 to 60 minutes before activities such as eating or shopping. Usual adult dosages for the agents used to treat myasthenia gravis are • Neostigmine—15 to 375 mg/day in divided doses • Pyridostigmine—60 to 1500 mg/day in divided doses (Burchum 131)
3. The nurse is caring for a patient with a suspected overdose of pancuronium, which was used during surgery. Which drug does the nurse anticipate will be used as a reversal agent? Neostigmine [Prostigmin] Atropine Pralidoxime [DuoDote] Dobutamine [Dobutrex]
Neostigmine [Prostigmin]
Pharmacokinetics of neostigmine (Prostigmin)
Neostigmine may be administered orally or by injection (IM, IV, subQ). Because neostigmine carries a positive charge, the drug is poorly absorbed following oral administration. Once absorbed, neostigmine can reach sites of action at the NMJ and peripheral muscarinic receptors, but cannot cross the blood-brain barrier to affect the CNS. Duration of action is 2 to 4 hours. Neostigmine is eliminated by enzymatic degradation by cholinesterase. (Burchum 128)
8. A nurse is caring for a patient prescribed doxazosin [Cardura] for hypertension. Safety is a priority because of which associated adverse effect? Reflex tachycardia Heart palpitations Cardiac dysrhythmias Orthostatic hypotension
Orthostatic hypotension
Mechanism of Action for Muscarinic Antagonist for OAB (Anticholinergic Therapy) - oxybutynin (Ditropan XL)
Oxybutynin [Ditropan XL, Gelnique, Oxytrol] is an anticholinergic agent that acts primarily at M3 muscarinic receptors. The drug is approved only for OAB. Benefits derive from blocking M3 receptors on the bladder detrusor. Oxybutynin is rapidly absorbed from the GI tract, achieving peak plasma levels about 1 hour after dosing. However, despite rapid absorption, absolute bioavailability is low (about 6%) because oxybutynin undergoes extensive first-pass metabolism—both in the gut wall and liver—primarily by CYP3A4, the 3A4 isoenzyme of cytochrome P450. One metabolite—N-desethyloxybutynin—is highly active, especially against muscarinic receptors in the salivary glands. Oxybutynin is very lipid soluble; therefore, it can penetrate the blood-brain barrier. The drug has a short half-life (2 to 3 hours), and hence multiple daily doses are required. (Burchum 122)
4. Which label most aptly describes the drug atropine [Sal-Tropine]? Cholinergic Parasympatholytic Muscarinic agonist Parasympathomimetic
Parasympatholytic
Therapeutic Uses for Propranolol & Metoprolol - Beta Blockers
Practically all of the applications of propranolol are based on blockade of beta1 receptors in the heart. The most important indications are hypertension, angina pectoris, cardiac dysrhythmias, and myocardial infarction. The role of propranolol and other beta blockers in these disorders is discussed in Chapters 47, 49, 51, and 53. Additional indications include prevention of migraine headache and "stage fright." (Burchum 161) The primary indication for metoprolol is hypertension. The drug is also approved for angina pectoris, heart failure, and myocardial infarction. (Burchum 164)
Actions and Uses for Prazosin - Alpha Blocker
Prazosin [Minipress], our prototype, is a competitive antagonist that produces selective blockade of alpha1-adrenergic receptors. The result is dilation of arterioles and veins, and relaxation of smooth muscle in the bladder neck (trigone and sphincter) and prostatic capsule. Prazosin is approved only for hypertension, but it can also benefit men with BPH. (Burchum 158)
2. The nurse notices significant edema surrounding and proximal to the peripheral intravenous (IV) site where epinephrine is being infused. Which action would the nurse anticipate first? Prepare to administer phentolamine [Regitine]. Ensure that naloxone [Narcan] is available. Institute the protocol for congestive heart failure (CHF). Monitor the blood urea nitrogen (BUN), creatinine, and potassium levels.
Prepare to administer phentolamine [Regitine].
Adverse Effects for Propranolol & Metoprolol - Beta Blockers
Propranolol Bradycardia. Beta1 blockade in the heart can cause bradycardia. Heart rate should be assessed before each dose. 163If the heart rate is below normal, the drug should be held and the prescriber should be notified. If necessary, heart rate can be increased by administering atropine and isoproterenol. AV Heart Block. By slowing conduction of impulses through the AV node, propranolol can cause AV heart block. The drug is contraindicated for patients with preexisting AV block (if the block is greater than first degree). Heart Failure. In patients with heart disease, suppression of myocardial contractility by propranolol can result in heart failure. Patients should be informed about the early signs of heart failure (shortness of breath on mild exertion or when lying supine, night coughs, swelling of the extremities, weight gain from fluid retention) and instructed to notify the prescriber if these occur. Propranolol is generally contraindicated for patients with preexisting heart failure (although other beta blockers are used to treat heart failure). Rebound Cardiac Excitation. Abrupt withdrawal of propranolol can cause rebound excitation of the heart, resulting in tachycardia and ventricular dysrhythmias. This problem is especially dangerous for patients with preexisting cardiac ischemia. To avoid rebound excitation, propranolol should be withdrawn slowly by giving progressively smaller doses over 1 to 2 weeks. Patients should be warned against abrupt cessation of treatment. In addition, they should be advised to carry an adequate supply of propranolol when traveling. Bronchoconstriction. Blockade of beta2 receptors in the lungs can cause bronchoconstriction. As a rule, increased airway resistance is hazardous only to patients with asthma and other obstructive pulmonary disorders. Inhibition of Glycogenolysis. Blockade of beta2 receptors in skeletal muscle and the liver can inhibit glycogenolysis. This effect can be dangerous for people with diabetes (see below). CNS Effects. Because of its lipid solubility, propranolol can readily cross the blood-brain barrier, and hence has ready access sites in the CNS. However, although propranolol is reputed to cause a variety of CNS reactions—depression, insomnia, nightmares, and hallucinations—these reactions are, in fact, very rare. Because of the possible risk of depression, prudence dictates avoiding propranolol in patients who already have this disorder. Effects in Neonates. Propranolol crosses the placental barrier. Using propranolol and other beta blockers during pregnancy may put the neonate at risk of bradycardia, respiratory distress, and hypoglycemia. Neonates should be closely monitored for these effects. (Burchum 161-163) Metoprolol Major adverse effects involve the heart. Like propranolol, metoprolol can cause bradycardia, reduced cardiac output, AV heart block, and rebound cardiac excitation following abrupt withdrawal. Also, even though metoprolol is approved for treating heart failure, it can cause heart failure if used incautiously. In contrast to propranolol, metoprolol causes minimal bronchoconstriction and does not interfere with beta2-mediated glycogenolysis. (Burchum 164)
5. Why does the nurse anticipate administering metoprolol [Lopressor] rather than propranolol [Inderal] for diabetic patients who need a beta-blocking agent? Metoprolol is less likely to cause diabetic nephropathy. Propranolol causes both beta1 and beta2 blockade. Metoprolol helps prevent retinopathy in individuals with diabetes. Propranolol is associated with a higher incidence of foot ulcers.
Propranolol causes both beta1 and beta2 blockade.
8. Antimuscarinic poisoning can result from overdose of antihistamines, phenothiazines, and tricyclic antidepressants. Differential diagnosis is important, because antimuscarinic poisoning resembles which other condition? Epilepsy Diabetic coma Meningitis Psychosis
Psychosis
7. The nurse is preparing to administer medication to the following patients. Which medication should the nurse question before administering? Clonidine [Duraclon] to a patient with severe pain Guanfacine [Intuniv] to a patient with attention-deficit/hyperactivity disorder (ADHD) Reserpine to a patient with a history of depression Methyldopa [Aldomet] to a patient with a diagnosis of hypertension
Reserpine to a patient with a history of depression
6. Following the administration of guanfacine [Tenex], the nurse should assess for which effects? Constipation and tachycardia Sweating and vivid dreams Skin rash and headache Sedation and dry mouth
Sedation and dry mouth
4. A patient goes to the emergency department after using organophosphate insecticides improperly. What assessment finding would the nurse expect? Urinary retention Stool incontinence Mydriasis Flushed, dry skin
Stool incontinence
Therapeutic Uses of Succinylcholine - Depolarizing NMBA
Succinylcholine is used primarily for muscle relaxation during endotracheal intubation. Additionally, it is sometimes used off-label to decrease the strength of muscle contraction during electroconvulsive therapy. Because of its brief duration, succinylcholine is poorly suited for use in prolonged procedures, such as surgery, although it is approved for use in these situations. (Burchum 139)
Adrenergic Antagonist
The adrenergic antagonists cause direct blockade of adrenergic receptors. With one exception, all of the adrenergic antagonists produce reversible (competitive) blockade. Unlike many adrenergic agonists, which act at alpha- and beta-adrenergic receptors, most adrenergic antagonists are more selective. As a result, the adrenergic antagonists can be neatly divided into two major groups (Table 18-1): (1) alpha-adrenergic blocking agents (drugs that produce selective blockade of alpha-adrenergic receptors); and (2) beta-adrenergic blocking agents (drugs that produce selective blockade of beta receptors).* (Burchum 156)
Muscarinic Agonists (mimic) and Antagonists (block)
The muscarinic agonists bind to muscarinic receptors and thereby cause receptor activation. Since nearly all muscarinic receptors are associated with the parasympathetic nervous system, responses to muscarinic agonists closely resemble those produced by stimulation of parasympathetic nerves. Accordingly, muscarinic agonists are also known as parasympathomimetic agents. (Burchum 116) Muscarinic antagonists competitively block the actions of acetylcholine at muscarinic receptors. Because the majority of muscarinic receptors are located on structures innervated by parasympathetic nerves, the muscarinic antagonists are also known as parasympatholytic drugs. Additional names for these agents are antimuscarinic drugs, muscarinic blockers, and anticholinergic drugs. (Burchum 118)
4. The nurse is preparing to give terbutaline [Brethine] to prevent preterm labor. Which concepts are important to keep in mind when working with this drug? (Select all that apply.) Terbutaline must be given by a parenteral route. The selectivity of terbutaline is dose dependent. The patient may experience tremor with terbutaline. Terbutaline is a sympathomimetic drug. Bronchoconstriction is a potential adverse effect of terbutaline.
The selectivity of terbutaline is dose dependent. The patient may experience tremor with terbutaline. Terbutaline is a sympathomimetic drug.
Treatment for toxicity of irreversible cholinesterase inhibitors
Treatment involves the following: (1) mechanical ventilation using oxygen, (2) giving atropine to reduce muscarinic stimulation, (3) giving pralidoxime to reverse inhibition of cholinesterase (primarily at the NMJ), and (4) giving a benzodiazepine such as diazepam to suppress convulsions. (Burchum 131)
5. The nurse is caring for a patient receiving atropine. Which is a therapeutic indication for giving this drug? Use as a preanesthesia medication Treatment of tachycardias Prevention of urinary retention Reduction of intraocular pressure in glaucoma
Use as a preanesthesia medication
3. The nurse is caring for a patient receiving propranolol [Inderal]. Which clinical finding is most indicative of an adverse effect of this drug? A heart rate of 100 beats per minute Wheezing A glucose level of 180 mg/dL Urinary urgency
Wheezing
9. Antimuscarinic adverse effects include which of the following? (Select all that apply.) Xerostomia Blurred vision Diarrhea Decrease in intraocular pressure Anhidrosis
Xerostomia Blurred vision Anhidrosis - inability to sweat normally
Patient teaching for minimizing adverse effects of anticholinergics
Xerostomia (Dry Mouth). Decreased salivation can dry the mouth. Teach patients that xerostomia can be relieved by sipping fluids, chewing sugar-free gum, treating the mouth with a saliva substitute, and using an alcohol-free mouthwash. Owing to increased risk of tooth decay, advise patients to avoid sugared gum, hard candy, and cough drops. Blurred Vision. Paralysis of the ciliary muscle may reduce visual acuity. Warn patients to avoid hazardous activities if vision is impaired. Photophobia. Muscarinic blockade prevents the pupil from constricting in response to bright light. Keep hospital room lighting low to reduce visual discomfort. Advise patients to wear sunglasses outdoors. Urinary Retention. Muscarinic blockade in the urinary tract can cause urinary hesitancy or retention. Advise patients that urinary retention can be minimized by voiding just before taking anticholinergic medication. If urinary retention is severe, catheterization or treatment with bethanechol (a muscarinic agonist) may be required. Constipation. Reduced tone and motility of the gut may cause constipation. Advise patients that constipation can be reduced by increasing dietary fiber and fluids, and treated with a laxative if severe. Hyperthermia. Suppression of sweating may result in hyperthermia. Advise patients to avoid vigorous exercise in warm environments. Tachycardia. Blockade of cardiac muscarinic receptors can accelerate heart rate. Monitor pulse and report significant increases. (Burchum 126)
