Chapter 15, Cholinesterase Inhibitors and Their Use in Myasthenia Gravis
A nurse is teaching a group of nursing students about irreversible cholinesterase inhibitors. Which statement by a student indicates understanding of the teaching? "Diazepam is given to reverse inhibition of cholinesterase when overdose occurs." "Irreversible cholinesterase inhibitors are rapidly absorbed by all routes." "These agents are often used to treat glaucoma." "Toxic doses of these agents produce an anticholinergic crisis."
ANS: B Almost all of these agents are highly lipid soluble, making them readily absorbed from all routes of administration. Diazepam is used during overdose but only to control seizures and not to reverse effects. The only clinical use for these agents is to treat glaucoma, but this use is limited. Toxic doses of these agents produce a cholinergic, not an anticholinergic, crisis.
A nurse is helping a nursing student who is administering a medication to a patient with myasthenia gravis. Which statement by the student indicates the need for further teaching? "I will ask the patient to sip some water before giving the medication." "I will let the patient sleep after giving the medication, because rest is important." "I will record muscle strength assessments before and after I give the medication." "I will report excessive salivation to the patient's prescriber."
ANS: B An important assessment indicating the medication's effectiveness is evaluating a patient'sability to raise the eyelids. Letting the patient sleep, even though rest is important, would prevent the nurse from making this assessment. To make sure the patient can safely swallow a pill, the nurse must evaluate swallowing ability by asking the patient to take a sip of water. Muscle strength assessments before and after medication administration help the nurse evaluate themedication's effectiveness. Excessive salivation may be a sign of drug toxicity and should bereported.
A patient with myasthenia gravis who is taking a cholinesterase inhibitor is being admitted to the intensive care unit and is on mechanical ventilation. The prescriber has ordered a challenge dose of edrophonium to distinguish between a myasthenic crisis and a medication overdose. The nurse will expect to do what? Administer neostigmine if muscle strength decreases. Be prepared to administer atropine if muscle weakness increases. Give a second dose of edrophonium if no improvement is seen. Give pralidoxime (Protopam) if cholinergic symptoms worsen.
ANS: B Edrophonium is an ultra-short-acting cholinesterase inhibitor used to distinguish between a myasthenic crisis and a cholinesterase inhibitor overdose, because weakness or paralysis can occur with both. If the symptoms are intensified and muscle weakness increases, the crisis is cholinergic, meaning that the patient is having toxic effects from the cholinesterase inhibitor and needs atropine as an antidote. Neostigmine would be given if the patient shows improved muscle strength, because that would indicate that the patient's symptoms are the result of a myastheniccrisis. A second dose of edrophonium would only worsen the symptoms. Pralidoxime is used to treat poisoning caused by irreversible cholinesterase inhibitors.
A patient who has myasthenia gravis will be taking neostigmine (Prostigmin). What will the nurse emphasize when teaching this patient about the medication? "Stop taking the drug if you have diarrhea." "Take a supplementary dose before exercise." "Use atropine if you have excessive salivation." "Withhold the dose if ptosis occurs."
ANS: B Neostigmine doses must be adjusted continually, and patients usually need supplemental doses before exertion; therefore, patients must be taught how to modify doses as needed. Increased gastrointestinal (GI) secretions can cause loose stools; this is a known adverse effect that does not warrant stopping the drug. Atropine will help with excessive salivation but should not be used routinely, because it can mask the early signs of anticholinesterase overdose. Ptosis is one of the symptoms of myasthenia gravis and is an indication for taking neostigmine.
Two nurses are discussing the major differences between physostigmine (Antilirium) and neostigmine (Prostigmin). One nurse correctly makes which statement about physostigmine (Antilirium)? "It is not effective for treating poisoning by muscarinic blocking drugs." "It can readily cross the blood-brain barrier." "It does not cause any side effects." "It can be given by all routes."
ANS: B The basic pharmacology of physostigmine is nearly identical to that of neostigmine, except that physostigmine readily crosses membranes, including the blood-brain barrier; neostigmine does not. Physostigmine and neostigmine are both effective for treating poisoning by muscarinic blocking drugs. Neither physostigmine nor neostigmine is devoid of side effects. Physostigmine can be given only intramuscularly (IM) or intravenously (IV); neostigmine is given orally (PO), IM, IV, and subcutaneously (subQ).
A nurse working in the emergency department is assigned to a child who is arriving by ambulance after being involved in a spill of organophosphate insecticides. What will the nurse expect to be the initial priority for treating this child? Administering diphenhydramine to control secretions Giving diazepam to control seizures Providing mechanical ventilation and oxygen Reporting the spill to the Environmental Protection Agency
ANS: C All of these courses of action may be part of the treatment. However, the initial concern is to prevent death from apnea caused by laryngospasm, bronchoconstriction, and paralysis leading to apnea; therefore, maintaining an airway is the most important consideration. Pralidoxime is the specific antidote and should be given next. Atropine is used to control secretions. Diazepam is given when seizures occur. Reporting the accident to the proper authorities is not a priority during a life-threatening emergency.
A nurse is teaching a new emergency department nurse about emergency medications. When asked to describe the uses of pralidoxime (Protopam), the new nurse makes which correct statement? "It exerts its greatest effects at muscarinic and ganglionic sites." "It is used to treat poisoning by reversible cholinesterase inhibitors." "It may not be effective if not given immediately." "It reverses the effects of organophosphate insecticides in the central nervous system."
ANS: C Pralidoxime must be given soon after organophosphate poisoning has occurred because of a process called aging, in which the bond between the organophosphate inhibitor and cholinesterase increases in strength, making pralidoxime ineffective. For some of these poisons, aging can occur within minutes. Pralidoxime has its greatest effects at the neuromuscular junction, not the muscarinic and ganglionic sites. It is used to treat poisoning by irreversiblecholinesterase inhibitors. It does not cross the blood-brain barrier and thus does not have effects in the CNS.
A nurse is caring for a patient who has myasthenia gravis. The prescriber has ordered neostigmine (Prostigmin). An important initial nursing action before administration of the medication includes assessing: the ability to raise the eyelids. level of fatigue. skeletal muscle strength. swallowing ability.
ANS: D Many patients hospitalized for myasthenia gravis do not have the muscle strength to swallowwell and need a parenteral form of the medication; therefore, assessing the patient's ability toswallow is an important initial safety measure. Evaluating the patient's ability to raise theeyelids, level of fatigue, and skeletal muscle strength are all important assessments both before drug administration and during drug treatment, because they indicate the effectiveness of the drug and help determine subsequent doses.
A patient is experiencing toxic side effects from atropine, including delirium and hallucinations. Which medication will the nurse expect to administer? Donepezil (Aricept) Edrophonium (Reversol) Neostigmine (Prostigmin) Physostigmine
ANS: D Physostigmine is the drug of choice for treating poisoning from atropine and other drugs thatcause muscarinic blockade. Donepezil is used to treat Alzheimer's disease. Edrophonium is usedto distinguish between a myasthenic crisis and a cholinesterase inhibitor overdose. Neostigmine does not cross the blood-brain barrier and would not effectively treat this patient's CNSsymptoms.
