Chapter 12 CNS Depressant and Muscle Relaxants PDF

Chapter 12 Central Nervous System Depressants and Muscle Relaxants  CNS Depressants Sedatives Drugs that have an inhibitory effect on the CNS to the degree that they reduce: Nervousness Excitability Irritability...

Chapter 12 Central Nervous System Depressants and Muscle Relaxants  CNS Depressants Sedatives Drugs that have an inhibitory effect on the CNS to the degree that they reduce: Nervousness Excitability Irritability 2  CNS Depressants (Cont.) Hypnotics Cause sleep Much more potent effect on CNS than sedatives A sedative can become a hypnotic if it is given in large enough doses. 3  CNS Depressants (Cont.) Sedative-hypnotics: dose dependent At low doses, calm the CNS without inducing sleep. At high doses, calm the CNS to the point of causing sleep. Classified into three main groups: Barbiturates Benzodiazepines Miscellaneous drugs 4  Sleep Transient, reversible, and periodic state of rest Decrease in physical activity and consciousness Normal sleep is cyclic and repetitive. A sleeping person is unaware of sensory stimuli within the immediate environment. Sleep architecture Rapid eye movement (REM) sleep Non-REM sleep REM interference REM rebound 5  CNS Depressants: Benzodiazepines (Cont.) Classified as either: Sedative-hypnotic Anxiolytic (medication that relieves anxiety) Five benzodiazepines commonly used as sedative-hypnotic drugs 6  Benzodiazepines: Mechanism of Action Depress CNS activity Affect hypothalamic, thalamic, and limbic systems of the brain Benzodiazepine receptors Gamma-aminobutyric acid (GABA) Do not suppress rapid eye movement (REM) sleep as much as barbiturates do Do not increase metabolism of other drugs 7  Benzodiazepines: Drug Effects Calming effect on the CNS Useful in controlling agitation and anxiety Reduce excessive sensory stimulation, inducing sleep Induce skeletal muscle relaxation 8  Benzodiazepines: Indications Sedation Sleep induction Skeletal muscle relaxation Anxiety relief Anxiety-related depression 9  Benzodiazepines: Indications (Cont.) Treatment of acute seizure disorders Treatment of alcohol withdrawal Agitation relief Balanced anesthesia Moderate or conscious sedation 10  Benzodiazepines: Contraindications Drug allergy Narrow-angle glaucoma Pregnancy 11  Benzodiazepines: Adverse Effects Mild and infrequent: Headache Drowsiness Dizziness Cognitive impairment Vertigo Lethargy Fall hazard for older adults “Hangover” effect or daytime sleepiness 12  Audience Response System Question #1 When providing education to the patient on the use of a benzodiazepine medication, the nurse will include which information? A. These medications have little effect on the normal sleep cycle. B. Using this medication may cause drowsiness the next day. C. It is safe to drive while taking this medication. D. These drugs are safe to use with alcohol. NOTE: No input is required to proceed. 13  Benzodiazepines: Toxicity and Overdose Somnolence Confusion Coma Diminished reflexes Do not cause hypotension and respiratory depression unless taken with other CNS depressants Treatment symptomatic and supportive Flumazenil as an antidote 14  Diazepam (Valium) First clinically available benzodiazepine drug. It has varied uses Treatment of anxiety Procedural sedation and anesthesia adjunct Anticonvulsant therapy Skeletal muscle relaxation Available in multiple forms: Oral Rectal Injectable 15  Midazolam (Versed) Used preoperatively and for moderate sedation Causes amnesia and anxiolysis (reduced anxiety) as well as sedation Normally administered by injection in adults Liquid oral dosage form is also available for children. High-alert medication 16  Temazepam (Restoril) Intermediate-acting benzodiazepine One of the metabolites of diazepam Normally induces sleep within 20 to 40 minutes Long onset of action, so it is recommended that patients take it about 1 hour prior to going to bed Still an effective hypnotic; however, it has been replaced by newer drugs 17  Nonbenzodiazepine: Eszopiclone First hypnotic to be FDA (Lunesta) approved for long- term use Designed to provide a full 8 hours of sleep Considered a short- to intermediate-acting agent Patients should allot 8 hours of sleep time and should avoid taking hypnotics when they must awaken in less than 6 to 8 hours. 18  Nonbenzodiazepine: Ramelteon (Rozerem) Structurally similar to the hormone melatonin: works as an agonist at melatonin receptors in the CNS Technically, it is not a CNS depressant; used as hypnotic Not classified as a controlled substance Indicated for patients who have difficulty with sleep onset rather than sleep maintenance 19  Nonbenzodiazepine: Zolpidem (Ambien) Short-acting nonbenzodiazepine hypnotic Lower incidence of daytime sleepiness compared with benzodiazepine hypnotics Ambien CR is a longer acting form with two separate drug reservoirs. Concerns about somnambulation (sleep- walking) 20  Barbiturates First introduced in 1903; were the standard drugs for insomnia and sedation Habit forming; low therapeutic index Only a few are commonly used today partly because of the safety and efficacy of benzodiazepines 21  Audience Response System Question #2 Barbiturates have a low therapeutic index. How does the nurse interpret this? A. Low doses are not therapeutic. B. The toxic range is narrow. C. They are habit forming. D. The effective, safe dosage range is narrow. NOTE: No input is required to proceed. 22  Barbiturates: Mechanism of Action Site of action: brainstem (reticular formation) By potentiating the action of GABA, nerve impulses traveling in the cerebral cortex are inhibited. 23  Barbiturates: Indications Ultrashort acting Anesthesia for short surgical procedures Anesthesia induction Control of convulsions Reduction of intracranial pressure in neurologic patients Short acting Sedation and control of convulsive conditions Intermediate acting Sedation and control of convulsive conditions Long acting Epileptic seizure prophylaxis 24  Barbiturates: Contraindications Drug allergy Pregnancy Significant respiratory difficulties Severe kidney or liver disease Caution in older adults 25  Barbiturates: Adverse Effects Body system Adverse effects Cardiovascular Vasodilation, hypertension CNS Drowsiness, lethargy, vertigo Respiratory Respiratory depression, cough 26  Barbiturates: Adverse Effects (Cont.) Body system Adverse effects GI Nausea, vomiting, diarrhea, constipation Hematologic Agranulocytosis, thrombocytopenia Other Hypersensitivity reactions, Stevens-Johnson syndrome 27  Barbiturates: Adverse Effects (Cont.) Reduced REM sleep, resulting in: Agitation 28  Quiz Quick Question #3 An older adult patient taking multiple medications has a barbiturate added to his medication regimen. When administering a barbiturate to an older adult, what should the nurse expect? A. A decrease in dosages of the other medications B. The patient will experience increased amounts of REM sleep C. To administer half of the usual dose of the barbiturate D. Total relief of anxiety NOTE: No input is required to proceed. 29  Barbiturates: Toxicity and Overdose Overdose frequently leads to respiratory depression and subsequent respiratory arrest. Overdose produces CNS depression (sleep to coma and death). Can be therapeutic Anesthesia induction Uncontrollable seizures: “phenobarbital coma” 30  Barbiturates: Toxicity and Overdose (Cont.) Treatment of overdose Symptomatic and supportive Maintain adequate airway Assisted ventilation and oxygen therapy Fluids Pressor support Urine alkalization (raising urine pH) to hasten elimination 31  Barbiturates: Drug Interactions Additive effects Alcohol, antihistamines, benzodiazepines, opioids, tranquilizers Inhibited metabolism MAOIs prolong the effects of barbiturates. Increased metabolism (enzyme inducers) Reduces anticoagulant response, leading to possible clot formation 32  Pentobarbital (Nembutal) Long-acting drug Uses: preoperatively to relieve anxiety and provide sedation. Occasionally to control status epilepticus No longer used as a sedative hypnotic drug for insomnia 33  Phenobarbital Prototypical barbiturate Long-acting Uses: Prevention of generalized tonic-clonic seizures and febrile convulsions Hyperbilirubinemia in neonates Rarely used as sedative No longer recommended as a hypnotic 34  Nonprescription Over-the-Counter Hypnotics sleeping aids often contain antihistamines, which have CNS depressant effect. Doxylamine (Unisom) and diphenhydramine (Sominex), acetaminophen/diphenhydramine (Extra Strength Tylenol PM); melatonin As with other CNS depressants, concurrent use of alcohol can cause respiratory depression or arrest. 35  Muscle Relaxants Act to relieve pain associated with skeletal muscle spasms Majority are centrally acting. CNS is the site of action. Similar in structure and action to other CNS depressants Direct acting Act directly on skeletal muscle Closely resemble GABA 36  Muscle Relaxants: Indications Relief of painful musculoskeletal conditions Muscle spasms Management of spasticity of severe chronic disorders (multiple sclerosis, cerebral palsy) IV dantrolene used for malignant hyperthermia Work best when used along with physical therapy 37  Muscle Relaxants: Adverse Effects Extension of effects on CNS and skeletal muscles Euphoria Lightheadedness Dizziness Drowsiness Fatigue Muscle weakness 38  Toxicity and Management of Overdose Primarily involve the CNS No specific antidote or reversal Best treated with conservative supportive measures If taken along with other CNS depressants Adequate airway must be maintained EKG monitoring Administer fluids to avoid crystalluria 39  Interactions Caution with other CNS depressants Benzodiazepines Alcohol 40  Common Muscle Relaxants Baclofen (Lioresal) Cyclobenzaprine (Flexeril) Dantrolene (Dantrium) Metaxalone (Skelaxin) Tizanidine (Zanaflex) Carisoprodol (Soma) Chlorzoxazone (Paraflex) Methocarbamol (Robaxin) 41  Quiz Quick Question #4 Which statement regarding muscle relaxants does the nurse identify as being accurate? A. Baclofen (Lioresal) is available as an injectable form for use with an implantable pump device. B. Cyclobenzaprine (Flexeril) produces little sedation. C. Patients taking muscle relaxants are at high risk of developing hypertension. D. Patients taking muscle relaxants should be told to stop taking the medication if they feel sleepy. NOTE: No input is required to proceed. 42  Baclofen (Lioresal) Oral and injectable forms Treat chronic spastic muscular conditions Implantable baclofen pump device; a test dose is given to confirm a positive response 43  Cyclobenzaprine (Flexeril) Oral and extended release oral form (Amrix) Centrally acting muscle relaxer Most common used muscle relaxer Can cause marked sedation 44  Nursing Implications Before beginning therapy, obtain a thorough history regarding allergies, use of other medications, health history, and medical history. Obtain baseline vital signs and I&O, including supine and erect blood pressure. Assess for potential disorders and conditions that may be contraindications and for potential drug interactions. 45  Nursing Implications (Cont.) Give hypnotics 30 to 60 minutes before bedtime for maximum effectiveness in inducing sleep (depends on drug’s onset). Most benzodiazepines cause REM rebound and a tired feeling the next day; use with caution in older adults. Instruct patients to avoid alcohol and other CNS depressants. 46  Nursing Implications (Cont.) Check with the prescriber before taking any other medications, including over-the- counter medications. Rebound insomnia may occur for a few nights after a 3- to 4-week regimen has been discontinued. 47  Nursing Implications (Cont.) Safety is important: Keep side rails up or use bed alarms. Do not permit smoking. Assist patient with ambulation (especially older adults). Keep call light within reach. Monitor for adverse effects. Age-appropriate considerations 48  Nursing Implications (Cont.) Monitor for therapeutic effects: Increased ability to sleep at night Fewer awakenings Shorter sleep-induction time Few adverse effects, such as “hangover” effects Improved sense of well-being because of improved sleep For muscle relaxants: decreased spasticity, decreased rigidity 49