Central Nervous System Regulation, Mood, and Cognition
8.5 CNS Depressants
Open Resources for Nursing (Open RN)
CNS depressants can slow brain activity, making them useful for conditions related to seizures and anxiety. Barbiturates and benzodiazepines are examples of CNS depressants.
Barbiturates
Phenobarbital is an example of a barbiturate primarily used as a sedative and to treat seizure disorders. In high doses, it can be used to induce anesthesia, and overdosage can cause death. In the 1960s and 1970s, barbiturates were used to treat anxiety and insomnia, but are no longer used for these purposes due to their serious adverse effects. Barbiturates are controlled substances under the Pharmacy Operations and Drug Scheduling Act. However, the misuse of barbiturates continues to occur with street use as a “downer” to counteract the effect of cocaine and methamphetamine.
Mechanism of Action
Barbiturates produce sedation and drowsiness by altering cerebellar function and depressing the actions of the brain and sensory cortex.
Indications for Use
Primarily used as an anticonvulsant. Also used as a sedative and may also be used as a pre-anesthetic agent.
Nursing Considerations Across the Lifespan
Do not use it for children less than 1 month of age. Barbiturates may harm the fetus during pregnancy. Avoid use in geriatric clients.
Adverse/Side Effects
Clients may experience CNS depression, suicidal thoughts or behaviors, GI disturbances, rashes, or some blood disorders that can be fatal. The concomitant use of alcohol or other CNS depressants may produce additive CNS depressant effects that can cause death. Barbiturates can be habit-forming.
Contraindicated for use in clients with severe renal and hepatic disorders, severe respiratory depression, dyspnea or airway obstruction, and porphyria.
Client Teaching & Education
The client should be advised to take the prescribed medication as directed. Clients who undergo prolonged therapy should not discontinue treatment abruptly as this may cause the onset of seizure activity. These medications may cause drowsiness and should not be taken with alcohol or other CNS depressants. Female clients using oral contraceptives should also use non-hormonal-based contraceptives during therapy involving barbiturate use.
Overdosage
The onset of symptoms following a toxic oral exposure to phenobarbital may not occur until several hours following ingestion. If an overdose occurs, consult with a Poison Information Center (1-800-567-8911).[1],[2]
Now let’s take a closer look at the medication grid for phenobarbital in Table 8.5a.[3]
Medication cards like this are intended to assist students to learn key points about each medication. Because information about medication is constantly changing, nurses should always consult evidence-based resources to review current recommendations before administering specific medication. Basic information related to each class of medication is outlined below. Prototype or generic medication examples are also hyperlinked to a free resource at Daily Med. On the home page, enter the drug name in the search bar to read more about the medication.
Table 8.5a Phenobarbital Medication Card [4][5][6][7]
Benzodiazepines
Lorazepam, a benzodiazepine with antianxiety, sedative, and anticonvulsant effects, is available for oral, intramuscular, or intravenous routes of administration. Benzodiazepines are controlled substances because they have a potential for abuse and may lead to dependence.
Mechanism of Action
Benzodiazepines bind to specific GABA receptors to potentiate the effects of GABA.
Indications for Use
Benzodiazepines are used for sedation, anti-anxiety, and anticonvulsant effects. Lorazepam injection is indicated for the treatment of status epilepticus. It may also be used in adult clients for pre-anesthetic medication to produce sedation (sleepiness or drowsiness), relieve anxiety, and decrease the ability to recall events related to the day of surgery. Oral lorazepam is used to treat anxiety disorders.
Nursing Considerations Across the Lifespan
Benzodiazepines may cause fetal harm when administered to pregnant women. Children and the elderly are more likely to experience paradoxical reactions to benzodiazepines such as tremors, agitation, or visual hallucinations. Elderly or debilitated clients may be more susceptible to the sedative and respiratory depressive effects of lorazepam. Therefore, these clients should be monitored frequently and have their dosage adjusted carefully according to the client’s response; the initial dosage should not exceed 2 mg. Dosage for clients with severe hepatic insufficiency should be adjusted carefully according to client response.
Adverse/Side Effects
A Black Box Warning states that concomitant use of benzodiazepines and opioids may result in profound sedation, respiratory depression, coma, and death.
The most important risk associated with the intravenous use of lorazepam injection is respiratory depression. Accordingly, airway patency must be assured and respiration monitored closely. Ventilatory support should be given as required. The additive central nervous system effects of other drugs, such as phenothiazines, narcotic analgesics, barbiturates, antidepressants, scopolamine, and monoamine-oxidase inhibitors should be considered when these other drugs are used concomitantly with, or during the period of recovery from, lorazepam injection. Sedation, drowsiness, respiratory depression (dose dependant), hypotension, and unsteadiness may occur with oral dosages as well. The use of benzodiazepines may lead to physical and psychological dependence. Abrupt termination of treatment may be accompanied by withdrawal symptoms. Benzodiazepines should be prescribed for short periods only (e.g., 2 to 4 weeks). Treatment period should not be extended without reevaluation of the need for continued therapy.
Overdosage
Overdosage of benzodiazepines is usually manifested by varying degrees of central nervous system depression, ranging from drowsiness to coma. Treatment of overdosage is mainly supportive until the drug is eliminated from the body. Vital signs and fluid balance should be carefully monitored in conjunction with close observation of the client. An adequate airway should be maintained and assisted respiration used as needed. The benzodiazepine antagonist flumazenil may be used for hospitalized clients in the management of benzodiazepine overdose. There is a risk of seizure in association with flumazenil treatment, particularly in long-term benzodiazepine users. If an overdose occurs, consult with a Poison Information Center (1-800-567-8911).[8]
Client Teaching & Education
Clients who receive lorazepam should be cautioned that driving a motor vehicle, operating machinery, or engaging in hazardous or other activities requiring attention and coordination should be delayed for 24 to 48 hours following administration or until the effects of the drug, such as drowsiness, have subsided. Clients should be advised that if they get out of bed unassisted within 8 hours of receiving lorazepam, they risk falling and potentially sustaining injury. Alcoholic beverages should not be consumed for at least 24 to 48 hours after receiving lorazepam injectable due to the additive effects on central nervous system depression seen with benzodiazepines in general. Elderly clients should be instructed that lorazepam injection may make them very sleepy for a period longer than 6 to 8 hours following surgery.
Now let’s take a closer look at the medication grid for lorazepam in Table 8.5b.[9]
Clinical Reasoning and Decision-Making Activity 8.5
A client who has been experiencing panic attacks is prescribed lorazepam. Upon further discussion with the client, the nurse discovers that the client is planning to go on a cruise with her husband next week and plans to use a scopolamine patch to control nausea. The client states, “I can’t wait to relax on the cruise ship and have a margarita as we leave port!”
What important client education should the nurse provide to the client about the new prescription for lorazepam?
Note: Answers to the Critical Thinking activities can be found in the “Answer Key” sections at the end of the book.
Media Attributions
- phenobarbital
- lorazepam
- This work is a derivative of Daily Med by U.S. National Library of Medicine in the public domain. ↵
- Drugs.com (2019, February 5). Barbiturates. https://www.drugs.com/drug-class/barbiturates.html ↵
- This work is a derivative of Daily Med by U.S. National Library of Medicine in the public domain. ↵
- This work is a derivative of Daily Med by U.S. National Library of Medicine in the public domain. ↵
- RNPedia. (2021). https://www.rnpedia.com ↵
- OpenMD.Com at www.openmd.com ↵
- uCentral from Unbound Medicine. https://www.unboundmedicine.com/ucentral ↵
- This work is a derivative of Daily Med by U.S. National Library of Medicine in the public domain. ↵
- This work is a derivative of Daily Med by U.S. National Library of Medicine in the public domain. ↵
- This work is a derivative of Daily Med by U.S. National Library of Medicine in the public domain. ↵