Transcript Chapter 22
Chapter 22 Drugs Affecting the Central Nervous System Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Neurotransmitters Cause electrical depolarization and passage of signal to next neuron Most are returned to releasing nerve terminal and “recycled” Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Neurotransmitters (cont’d) Factors impacting effect: Amount released Type/quantity of transport proteins Previous release Modifiers present Reuptake process Modulating interneurons Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Psychiatric Medications Antidepressants Selective serotonin reuptake inhibitors (SSRIs) are first-line treatment Newer: Serotonin norepinephrine reuptake inhibitors Depression Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Psychiatric medications (cont’d) Mood stabilizers Used primarily for bipolar disorder • Alternating depression/mania (or hypomania) Drugs: lithium, valproic acid, carbamazepine, gabapentin, lamotrigine, and antipsychotics Main side effect is sedation Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Psychiatric medications (cont’d) Antipsychotics Increase dopamine levels in brain Psychotic disorders • Impaired reality • Schizophrenia • Psychosis associated with depression or mania Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Psychiatric medications (cont’d) Antipsychotics (cont’d) Newer agents more tolerable • Risperidone • Olanzapine • Quetiapine Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Psychiatric medications (cont’d) Drugs for Alzheimer’s dementia: cholinesterase inhibitors Increase acetylcholine levels in brain Drugs: • Donepezil • Tacrine • Galantamine • Rivastigmine May cause gastrointestinal (GI) side effects Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Psychiatric medications (cont’d) Anxiolytics Also used as amnesics May augment opioid respiratory depression Benzodiazepines • Hyperpolarize neurons • Good for anesthesia induction • Prevent “unpleasant recall” • Terminate seizures/increase threshold Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Psychiatric Medications (cont’d) Barbiturates Toxic potential and rapid tolerance • Depress neuron activity • High risk of addiction and abuse Used for • Anesthesia induction • Hypnotics • seizures Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Psychiatric Medications (cont’d) Other hypnotics Often used to induce sleep Hypnotics to induce sleep are generally recommended for 1 to 2 weeks Eszopiclone • New drug • Approved for long-term use Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Ethyl Alcohol Socially acceptable nonprescription sedativehypnotic Also has disinhibiting effect In excess = general anesthetic 400 to 600 mg/dl = respiratory arrest Delirium tremens CNS hyperactivity on withdrawal Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Pain Treatment Pain is now the fifth vital sign The pain experience Pain • Input from CNS pain receptors Suffering • Emotional response to pain experience Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Pain Treatment (cont’d) Nonsteroidal antiinflammatory drugs (NSAIDs) Affect hypothalamus and inhibit production of inflammatory mediators at pain site Some may cause gastric irritation/ulceration Salicylates are oldest (aspirin) Acetaminophen (Tylenol) Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Pain Treatment (cont’d) Opioid analgesics Derivatives of naturally occurring opium Used to treat moderate to severe pain Exert effect by binding to receptors for endogenous opioids (endorphins and enkephalins) Popular drugs of abuse Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Pain Treatment (cont’d) Routes of opioid administration As needed (by nurse) Patient-controlled analgesia (PCA) pumps • Better to keep control of pain than regain control Opioid inhalation • Decreases dyspnea in advanced respiratory failure • Has shown good clinical effect on cancer patients without lung disease Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Pain Treatment (cont’d) Local anesthetics Interrupt nerve signals (pain) from damaged area • Block Na channels along nerve cells Also useful as analgesia and for terminating cardiac conduction abnormalities Can suppress irritant tracheal cough response Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Pain Treatment (cont’d) Epidural analgesia Infusions of local anesthetics/opioids improve postoperative pain therapy and outcome Provides better pain control versus systemic analgesics Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Pain Treatment (cont’d) Combinations of analgesic classes Prescription combinations of NSAIDs and opioids are widely available Separate dosing may prove better with various side effects, toxicities, and half-lives • More troublesome for patients to take independently Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Chronic Pain Syndromes Central sensitization can occur secondary to acute pain from surgery or trauma Hyperesthesia, hyperpathia, and allodynia Treatment during acute phase may reduce likelihood of neuropathic problem later Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Chronic Pain Syndromes (cont’d) Characteristics of neuropathic pain Evidence of primary injury Pain involving body area with sensory loss Pain characterized as burning, electric, or shooting Dysesthesias in the area Sympathetic hyperactivity Hyperalgesia, hyperpathia, and allodynia Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Anesthesia Drug-induced absence of perception Usually inhaled or IV Gases and volatile liquids Depth is determined by response to painful stimuli Change in heart rate or blood pressure Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Anesthesia (cont’d) Conscious sedation Patient remains conscious • Able to communicate and protect airway • Ability may be lost during procedure Goal is improved patient comfort and outcome Conscious sedation standards are required by Joint Commission on Accreditation of Healthcare Organizations (JCAHO) Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Anesthesia (cont’d) Standards for providing conscious sedation Resuscitation equipment and trained personnel immediately available Conscious sedation requires >1 person Deep sedation/general anesthesia require at least 3 people Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. CNS and Respiratory Stimulants Analeptic drugs Increase activity of brain Treat: narcolepsy, attention-deficit hyperactivity disorder (ADHD), obesity No clinical role in treating respiratory failure Mosby items and derived items © 2008, 2002 by Mosby, Inc., an affiliate of Elsevier Inc.