Mosby items and derived items © 2005, 2002 by Mosby, Inc. CHAPTER 12 Central Nervous System Depressants and Muscle Relaxants

Mosby items and derived items © 2005, 2002 by Mosby, Inc. CNS Depressants Sedatives or Hypnotics

Mosby items and derived items © 2005, 2002 by Mosby, Inc. CNS Depressants Sedatives Drugs that have an inhibitory effect on the CNS to the degree that they reduce: –Nervousness –Excitability –Irritability without causing sleep

Mosby items and derived items © 2005, 2002 by Mosby, Inc. CNS Depressants (cont'd) Hypnotics Calm or soothe the CNS to the point that they cause sleep A sedative can become a hypnotic if it is given in large enough doses

Mosby items and derived items © 2005, 2002 by Mosby, Inc. CNS Depressants (cont'd) Sedative-hypnotics—dose dependent At low doses, calm or soothe the CNS without inducing sleep At high doses, calm or soothe the CNS to the point of causing sleep

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Sleep Normal sleep is cyclic and repetitive A sleeping person is unaware of sensory stimuli within the immediate environment Rapid eye movement (REM) Non–rapid eye movement (non-REM) Sleep stages

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Table 12-2 Stages of Sleep

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Sedative-Hypnotics: Barbiturates First introduced in 1903; standard agents for insomnia and sedation Habit forming Only a handful commonly used today due in part to the safety and efficacy of benzodiazepines

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Barbiturates: Four Categories Ultrashort –mephobexital, thiamylal, thiopental Short –pentobarbital, secobarbital Intermediate –butabarbital Long –phenobarbital, mephobarbital

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Therapeutic Index Dosage range within which the drug is effective but above which is rapidly toxic Barbiturates have a very narrow therapeutic index

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Table 12-3 Barbiturates: Onset and Duration

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Barbiturates: Mechanism of Action Site of action –Brainstem (reticular formation) By inhibiting GABA, nerve impulses traveling in the cerebral cortex are also inhibited

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Barbiturates: Drug Effects Low doses: sedative effects High doses: hypnotic effects (also lowers respiratory rate) Notorious enzyme inducers – Stimulate liver enzymes that cause the metabolism or breakdown of many drugs

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Barbiturates: Indications Hypnotic Sedative Anticonvulsant Anesthesia for surgical procedures

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Barbiturates: Side Effects Body SystemEffects CNSDrowsiness, lethargy, vertigo, mental depression, coma RespiratoryRespiratory depression, apnea, bronchospasms, cough

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Barbiturates: Side Effects (cont'd) Body SystemEffects GINausea, vomiting, diarrhea constipation OtherAgranulocytosis, vasodilation, hypotension, Stevens-Johnson syndrome

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Barbiturates: Side Effects (cont'd) Reduce REM sleep, resulting in: –Agitation –Inability to deal with normal stress

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Barbiturates: Toxicity and Overdose Overdose frequently leads to respiratory depression, and subsequently, respiratory arrest Overdose produces CNS depression (sleep to coma and death) Can be therapeutic –Anesthesia induction –Uncontrollable seizures: “phenobarbital coma”

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Barbiturates: Drug Interactions Additive effects –ETOH, antihistamines, benzodiazepines, narcotics, tranquilizers Inhibited metabolism –MAOIs will prolong effects of barbiturates Increased metabolism –Reduces anticoagulant response, leading to possible clot formation

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Common Barbiturates butabarbital (Butisol) pentobarbital (Nembutol) phenobarbital (Luminal) secobarbital (Seconal)

Mosby items and derived items © 2005, 2002 by Mosby, Inc. CNS Depressants: Benzodiazepines Most frequently prescribed sedative- hypnotics Most commonly prescribed drug classes Favorable side effect profiles Efficacy Safety

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Benzodiazepines: Classification Classified as either: –Sedative-hypnotic –anxiolytic (medication that relieves anxiety)

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Benzodiazepines: Sedative-Hypnotic Types Long acting –estazolam (Prosom), quazepam (Doral) Short acting –flurazepam (Dalmane), temazepam (Restoril) –triazolam (Halcion)

Mosby items and derived items © 2005, 2002 by Mosby, Inc. CNS Depressants: Nonbenzodiazepine Hypnotics Zalepion (Sonata) and zolpidem (Ambien) Share many characteristics of benzodiazepines

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Benzodiazepines: Mechanism of Action Depress CNS activity Affect hypothalamic, thalamic, and limbic systems of the brain Benzodiazepine receptors Do not suppress REM sleep as much as barbiturates do Do not increase metabolism of other drugs

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Benzodiazepines: Drug Effects Calming effect on the CNS Useful in controlling agitation and anxiety Reduce excessive sensory stimulation, inducing sleep Induce skeletal muscle relaxation

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Benzodiazepines: Indications Sedation Sleep induction Skeletal muscle relaxation Anxiety relief Treatment of alcohol withdrawal

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Benzodiazepines: Indications (cont'd) Agitation Depression Epilepsy Balanced anesthesia

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Benzodiazepines: Side Effects Mild and infrequent Headache Drowsiness Dizziness Vertigo Lethargy Paradoxical excitement (nervousness) “Hangover effect”

Mosby items and derived items © 2005, 2002 by Mosby, Inc. CNS Depressants: Nursing Implications Before beginning therapy, perform 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 BPs Assess for potential disorders or conditions that may be contraindications, and for potential drug interactions

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications Give 15 to 30 minutes before bedtime for maximum effectiveness in inducing sleep Most benzodiazepines (except flurazepam) cause REM rebound and a tired feeling the next day; use with caution in the elderly Patients should be instructed to avoid alcohol and other CNS depressants

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications Check with physician before taking any other medications, including OTC medications It may take 2 to 3 weeks to notice improved sleep when taking barbiturates Rebound insomnia may occur for a few nights after a 3- to 4-week regimen has been discontinued

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications Safety is important –Keep side rails up or use bed alarms –Do not permit smoking –Assist patient with ambulation (especially the elderly) –Keep call light within reach Monitor for side effects

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications Monitor for therapeutic effects –Increased ability to sleep at night –Fewer awakenings –Shorter sleep-induction time –Few side effects, such as hangover effects –Improved sense of well-being because of improved sleep

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Muscle Relaxants Act to relieve pain associated with skeletal muscle spasms Majority are central acting –CNS is the site of action –Similar in structure and action to other CNS depressants Direct acting –Acts directly on skeletal muscle –Closely resembles GABA

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Muscle Relaxants: Indications Relief of painful musculoskeletal conditions –Muscle spasms –Management of spasticity of severe chronic disorders –Multiple sclerosis, cerebral palsy Work best when used along with physical therapy

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Muscle Relaxants: Indications (cont'd) dantrolene –Malignant hyperthermia crisis

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Muscle Relaxants: Side Effects Extension of effects on CNS and skeletal muscles –Euphoria –Lightheadedness –Dizziness –Drowsiness –Fatigue –Muscle weakness

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Common Muscle Relaxants baclofen (Lioresal) cyclobenzaprine (Flexeril) dantrolene (Dantrium) metaxalone (Skelaxin) tizanidine (Zanaflex)

Mosby items and derived items © 2005, 2002 by Mosby, Inc. Muscle Relaxants: Nursing Implications See others listed for CNS depressants