Week 3 ~ Central Nervous System Flashcards
What are 2 kinds of Analgesics?
Opioids
Nonsteroidial Anti Inflammatory Drugs (NSAIDS)
What is the definition of pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage
ACUTE: sudden onset and subsides once treated
PERSISTENT: Lasts longer than 6 weeks and difficult to treat
10 Different Types of Pain
- Somatic
- Phantom
- Visceral
- Superficial
- Referred
- Vascular
- Central
- Cancer
- Psychogenic
- Neruopathic
What are the 4 processes of the Pain Transmission Gate Theory?
Transduction
Transmission
Perception
Modulation
What is the Pain Transmission Gate Theory?
How impulses from the damaged tissues are sensed by the brain
Pain Management drugs are aimed at altering this system
In Pain Transduction what does the tissue release?
*Bradykinin
*Histamine
*Substance P
*Prostaglandins
*Serotonin
*Leukotrienes
~These stimulate nerve endings and starts the pain process
What are the 2 main pain fibres in Pain Transmission?
A-Delta Fibres
C Fibres
What do A-Delta Fibres do?
Sensitive to mechanical and thermal pain.
Transmit local and sharp pain
Stimulate the sympathetic nervous system
What do C Fibres do?
Sensitive to mechanical, thermal and chemical stimuli
Transmit poorly localized and dull pain
What happens in the Pain Perception phase?
Complex behavioural, psychological and emotional factors
Is controlled by the single gene and opioid receptor gene
Perception is diminished when there are many receptions and exacerbated when there are too few or missing ones. Relatively minor pain stimuli may be perceived as painful
What are two types of endogenous neurotransmitters?
Enkephalins
Endorphins
What happens in Pain Modulation?
The body produces endogenous neurotransmitters:
Enkephalins
Endorphins——-> Produced to fight pain —-> Bind to opioid receptors —-> Inhibit transmission of pain by closing the gate
What is Pain Tolerance?
The amount of pain a person can insure without interfering normal function
- Not a physiological function
- Is the point beyond which pain becomes unbearable
What is a Pain Threshold?
The level of stimulus needed to produce the perception of pain
*Measure of the physiological response of the nervous system
3 Chemical Categories of Opioids?
Meperidine
Methadone
Morphine
Opioid Drugs under the Meperidine Category
Meperidine
Fentanyl
Sufentanil
Alfentanil
Opioid Drugs under the Methadone Category?
Methadone
Propoxyphene
Opioid Drugs under the Morphine Category?
Morphine
Heroin
Hydromorphone
Codeine
Hydrocodone
Oxycodone
Opioid Analgesics Mechanism of Action: Three Classifications based on Actions
-Agonist: Bind to opioid pain receptor in the brain. Cause an
Analgesic response
-Partial Agonist: Bind to pain receptor. Cause a weaker neurological
Response then a full agonist
Agonist-Antagonist or mixed agonist
-Antagonist: Reverse the effects of these drugs on pain receptors.
Bind to pain receptor and exert no response
Competitive Antagonist
5 Types of Opioid Receptors?
Mu* Kappa* Delta* Sigma Epsilon
Indications for Opioid Analgesics
~Moderate to severe pain
~Used as adjuvant analgesic drugs to assist the primary drugs with pain relief:
1. NSAIDS
2. Antidepressants
3. Anticonvulsants
4. Corticosteroids
Opioids are also used for cough centre suppression or diarrhea
Contraindications for Opioid Analgesics?
~Known drug allergy
~Severe asthma or respiratory insufficiency
~Pregnancy
~Elevated Intracranial Pressure
Adverse Effects of Opioid Analgesics
Hypotension Palpations Flushing Nausea Vomiting Biliary Tract Urinary Retention Itching Respiratory Depression Aggravation of asthma Wheat Formation Sedation Disorientation Euphoria Tremors Lowered seizure thresholds
2 Opiate Antidote
Naloxone (Narcan)
Naltrexone (ReVia)
-Bind to opiate receptors and prevent a response
- Used for complete or partial reversal of opioid-induced
Respiratory depression
Opioid Tolerance
Common physiological result of chronic opioid treatment
Larger dose of opioids is required to maintain the same level of
Analgesia
Opiates cause a physical and psychological dependance
What are Analgesics?
Medications to relieve pain without causing loss of consciousness
Non-Opioid Analgesics: Acetaminophen
Has analgesic and antipyretic effects
Little to no anti inflammatory effects
Available OTC
Is a component of many combination products with opioids
Acetaminophen Mechanism of Action
Similar to the action of salicylates
Blocks pain impulses peripherally by inhibiting prostaglandins synthesis
Indications of Acetaminophen
Mild to moderate pain
Fever
Alternative for those who can’t take aspirin
Dosage of Acetaminophen
Healthy adults is 4000mg per day
Overdose causes hepatic necrosis or long term ingestion of large doses can cause nephropathy
What’s the antidote for Acetaminophen toxicity?
Acetylcysteine
Acetaminophen Drug Interactions
Dangerous interactions with alcohol
Other Hepatotoxic Drug
Liver Dysfunction
What are Anaesthetics?
Drugs that depress the central nervous system
~Depression of consciousness
~ Muscle relaxant
~Loss of responsiveness to sensory stimulation (including pain)
What is General Anaesthetic?
Drugs that induce a state in which the CNS is altered to produce varying degrees of:
~Depression of consciousness ~ Skeletal mm relaxation ~ Visceral Smooth mm relaxation
2 Types of General Anaesthetics?
Inhaled Anaesthetics: Volatile liquids or gases that are
Vaporized in oxygen and inhaled
Injectable Anaesthetic: Administered Intravenously
Inhaled Anaesthetics
Inhaled Gas: Nitrous Oxide (“laughing gas”)
Inhaled Volatile Liquids
~Desflurane (Suprame)
~ Halothane
Injectable Anaesthetics
Ketamine (Ketalar)
Propofol (Diprivan)
Thiopental (Pentothal)
- Isoflurane (Forane)
Indications for Injectable Anaesthetics
Uses:
~ To induce or maintain general anaesthesia
~ To induce amnesia
~ To reduce anxiety
~ As an adjunct to inhalation-type anaesthetics
Adjunctive Drugs for Injectable Anaesthetics
Opioid Analgesics
Benzodiazepine
Anticholinergic
Opioid Analgesic Drugs
Alfentanil (Alfenta)
Fentanyl
Meperidine (Demerol)
Morphine
Benzodiazepine Drugs
Diazepam
Lorazepam
Midazolam
Anticholinergic Drugs
Atropine
What is the Overton-Meyer Theory?
When a sufficient number of inhalation anaesthetic molecules dissolve in the lipid cell membrane.
Effects:
1. Orderly and systematic reduction of sensory and motor CNS
Function
2. Progressive depression of cerebral and spinal cord functions
General Anaesthetic Indications
Used during surgical procedures to create
Unconsciousness
Skeletal Muscular Relaxation
Visceral Smooth Muscle Relaxation
Rapid onset and quickly metabolized
Contraindications of General Anaesthetic
Known drug allergy
Pregnancy
Narrow Angle Glaucoma
Known susceptibility to malignant hyperthermia
General Anaesthetic Adverse Effects
Affect the heart, liver, kidneys, peripheral circulation, respiratory tract
Myocardial Depression
Malignant Hyperthermia
What is Malignant Hyperthermia?
Sudden elevation of body temperature greater than 40c, tachypnea, tachycardia, muscular rigidity
General Anaesthetic Drug Interactions
Anti hypertensives
B-Blockers
Tetracycline
What is Local Anaesthetic used for?
Used to a specific part of the body due to pain
Interferes with the nerve impulse transmitting to specific areas of the body. Doesn’t cause loss of consciousness
2 Types of Local Anaesthetic?
Topical
Parenteral (Spinal Injection)
2 Types of Parenteral Local Anaesthetic?
Central: Spinal or Intraspinal
Ie. Epidural or Intrathecal
Peripheral: Infiltration, nerve block, topical
4 Types of Parenteral Anaesthetic Drugs?
Lidocaine
Mepivacaine
Procaine
Tetracaine
Local Anaesthetic Drug Effects?
Paralysis ~
1st: Autonomic activity is lost
2nd: Then pain and other sensory functions are lost
3rd: Motor activity is lost
*As drug wears off the recovery occurs in reverse order
Motor –> Sensory –> Autonomic Acvitity
Local Anaesthetic Indications?
Surgical/Dental and Diagnostic Procedures
Treatment of certain types of chronic pain
Infiltration anaesthetic or nerve block anaesthetic
Infiltration Anaesthesia
Used in minor surgical or dental procedures
Given in a circular pattern
Injected intradermally, subcutaneously or submucosally across the
path of nerves supplying the targeted area
Nerve Block Anaesthesia
Used for surgical, dental and diagnostic procedures
Therapeutic management of pain
Injected directly into or around the nerve trunks or nerve ganglia that supply the area to be numbed
Local Anaesthetic Contraindications
Drug allergy
Spinal Headache
What are Neuromuscular Blocking Drugs?
Prevent nerve transmission in certain muscles resulting in paralysis of the muscle
Used with anaesthetics during surgery
Paralyze respiratory and skeletal muscles and so the patient is unable to breath on their own
Do not cause sedation of pain relief!
2 Types of Neuromuscular Blocking Drugs?
Depolarizing
Non Depolarizing
How Neuromuscular Blocking Drugs affect the body?
First sensation is muscles weakness followed by total paralysis
Smaller rapidly moving muscles like fingers and eyes are affected first and then limbs, neck and trunk
Then intercostal muscles and the diaphragm are affected resulting in cessation of respiration
Recovery of muscular activity will occur in reverse order
What are Sedatives?
Drugs that have an inhibitory effect on the CNS to reduce nervousness, excitability and irritability without causing sleep
What are Hypnotics?
Causes sleep.
A sedative can become a hypnotic if it is given in larger doses
What are Sedative-Hypnotics?
Dose dependant at low doses, they calm the CNS without inducing sleep and at high doses they calm the CNS to the point of causing sleep
Habit forming and have low therapeutic index
What are the sleep stages?
Rapid eye movement (REM) sleep
Non rapid eye movement (non-REM) sleep
4 Categories of Barbiturates?
- Ultrashort: Short surgical procedures
- Short: Sedative-hypnotic, control convulsive conditions
- Intermediate: Same as short
- Long: Sedative-hypnotic, epileptic seizures
Name of an Ultra Short Barbiturate?
Thiopental (Pentothal)
Name of a Short Barbiturate?
Pentobarbital
Name of an Intermediate Barbiturate?
Butalbital
Name of a Long Barbiturate?
Phenobarbital
What’s a Therapeutic Index?
Dosage range which the drug becomes effective but above that range rapidly becomes toxic
Barbiturates have a very narrow therapeutic index!
Barbiturate Mechanism of Action
Act primarily on the brain stem (reticular formation)
Inhibits gamma-aminobutyric acid (GABA)
Inhibit the nerve impulse travelling in the cerebral cortex
Barbiturate Drug Effects?
Low Doses = Sedative
High Doses = Hypnotic effects and lower respiratory rate
Enzyme Inducers = stimulate liver enzymes that cause the metabolism
Or breakdown of many drugs and shorten duration
Of action
Barbiturate Indications:
Sedative
Hypnotic
Anticonvulsant
Anaesthetics for surgical procedures
Barbiturate Contraindications
Known allergy
Pregnancy
Severe liver disease
Significant respiratory difficulties
Barbiturate Adverse Effects?
Nausea/vomiting
Diarrhea/constipation
Drowsiness/lethargy
Vertigo
Mental Depression
Respiratory Depression/Apnea
Bronchospasms/cough
Hypotension
Reduced REM sleep resulting in agitation
Barbiturate Toxicity and Overdose
Respiratory Arrest
CNS depression ranging from sleep to coma and death
Barbiturate Additive Effects
If ingested with the following it will intensify the CNS depression
Alcohol
Antihistamines
Opioids
Benzodiazepines
Barbiturate Inhibited Metabolism
Mono amine oxidase inhibitors (MAOIs) will prolong effects of barbiturates
Barbiturate Increased Metabolism
Reduces anticoagulant response leading to possible clot formation
What are Benzodiazepines?
Most commonly used sedative-hypnotic because of their favourable adverse effect
2 Classifications of Benzodiazepines?
Sedative-Hypnotic
Anxiolytics (Relieves Anxiety)
Benzodiazepine Sedative-Hypnotic Types
Long Acting:
Flurazepam (Apo-Flurazepam)
Short Acting:
Temazepam (Restoril)
Triazolam (Halcion)
Benzodiazepines Mechanism of Action
Depress CNS activity
Affect hypothalamic, thalamic and limbic systems of the brain
Activate Benzodiazepine receptors
Doesn’t suppress REM and doesn’t increase metabolism of other drugs!
Benzodiazepines Drug Effects
Calming effect on CNS
Useful in controlling agitation and anxiety
Reduce excessive sensory stimulation, inducing sleep
Induce skeletal muscle relaxation
Benzodiazepine Indications
Sedation
Sleep Inducing
Anxiety Relief
Depression
Skeletal muscle relaxation
Alcohol withdrawal
Epilepsy
Balanced Anesthesia
Moderate or conscious sedation
Contraindications of Benzodiazepines?
Known drug allergy
Pregnancy
Narrow angle glaucoma
Benzodiazepines Adverse Effects?
Mild/Infrequent:
Headache
Vertigo
Drowsiness/Dizziness
Lethargy
Fall hazard in frail elderly
Benzodiazepine Drug Interactions
Grapefruit and grapefruit juice alter drug absorption
Kava and Valerian further CNS depression
Other CNS depressants further CNS depression
Drugs under the Nonbarbiturate or Non Benzodiazepine Sedatives:
Buspirone
`Chloral Hydrate
Tizanidine
Paraldehyde
What is a Seizure?
Brief episode of abnormal electrical activity in the nerve cells of the brain
What are convulsions?
Involuntary spasmodic contractions of any or all voluntary muscles throughout the body including skeletal and facial muscles
What is Epilepsy?
Chronic and recurrent pattern of seizures
2 Types of Epilepsy’s?
Primary (Idiopathic)
` No apparent cause (50% of cases)
Secondary
` Distinct cause identified ie trauma, infection
Classification of Epilepsy
- Partial
` Simple
` Complex - Generalized
- Unclassified
- Status Epilepticus
What are Anti-Epileptic Drugs?
*Also known as anti-convulsants
Control and prevent seizures while maintaining quality of life and to minimize adverse effects
Usually lifelong
Serum drugs need to be measured
Anti-Epileptic Drugs Mechanism of Action
Exact mechanism is unknown and thought to alter the movement of sodium, potassium and calcium ions across nerve cells in the brain
Prevent degeneration
Spread of excessive electrical discharge from abnormally functioning nerve cells and protect surrounding normal cells
Reduce nerve stimulation and transmission of impulses from one nerve to the next
Anti-Epileptic Drug Adverse Effects?
Drowsiness
Vision Problems
Narrow Therapeutic Index
Anti-Epileptic Drug Interactions?
Increased bone marrow toxicity
Decrease in half life
Increase CNS depression
Breakthrough seizures
Increased or decreased drug levels
First Choice Anti-Epileptic Drugs
Carbamazepine
Phenobarbital
Phenytoin
Primidone
Valproic Acid
Some Second Choice Anti-Epileptic Drugs
Clonzepam
Levetiracetam
Clorazepate
