Pharmacology CNS and PNS Flashcards
Neurotransmitters Levels in Disease
-Acetylcholine, Dopamine, GABA, Glutamate, Norepinephrine, Serotonin (5-HT)
FA-OS p. 512
Acetylcholine
-Low in: Alzheimer’s
Dopamine
- Low in: Parkinson’s
- High in: Schizophrenia, mania, psychosis
GABA
-Low in: Anxiety, epilepsy
Glutamate
-High in: Alzheimer’s, Schizophrenia, epilepsy
Norepinephrine
- Low in: Major depressive disorder
- High in: Anxiety
Serotonin (5-HT)
- Low in: Major depressive disorder, bipolar disorder, anxiety
- High in: Schizophrenia
Neurotransmitter Levels in Alzheimer’s
FA-OS p. 512
- Low Acetylcholine
- High Glutamate
Neurotransmitter Levels in Schizophrenia
FA-OS p. 512
- High Dopamine
- High Glutamate
- High Serotonin
Neurotransmitter Levels in Parkinson’s
FA-OS p. 512
-Low Dopamine
Neurotransmitter Levels in Mania
FA-OS p. 512
-High Dopamine
Neurotransmitter Levels in Psychosis
FA-OS p. 512
-High Dopamine
Neurotransmitter Levels in Anxiety
FA-OS p. 512
- Low GABA
- High Norepinephrine
- Low Serotonin
Neurotransmitter Levels in Epilepsy
FA-OS p. 512
- Low GABA
- High Glutamate
Neurotransmitter Levels in Major Depressive Disorder
FA-OS p. 512
- Low Norepinephrine
- Low Serotonin
Neurotransmitter Levels in Bipolar Disorder
FA-OS p. 512
-Low Norepinephrine
An important site for the production of ACh in the brain
nucleus basalis of Meynert
Important sites of dopaminergic neurons in the brain
- Substantia nigra pars compacta
- Ventral tegmental area
Location of histaminergic neurons in the brain
-Ventral posterior hypothalamus (tuberomammillary nucleus)
Primary site of norepinephrine synthesis in the brain
-Locus ceruleus (found in the upper pons)
Area that releases serotonin to projections throughout the brain
-Raphe nucleus
General characteristics of neuromuscular junction blocking agents
- Used for skeletal muscle relaxation
- Site of action = neuromuscular junction
- Do NOT cause analgesia or unconsciousness (only paralysis)
- Structurally resemble ACh
- Bind ACh receptors on muscle
- Two classes: depolarizing agents and nondepolarizing agents
Depolarizing agent drug name
Succinylcholine
Succinylcholine mechanism
- Short acting (works within 30 sec and last 10 min)
- Depolarizing agent
- ACh receptor agonist
- Resistance to AChE allows it to remain bound to the receptor
- Limited by diffusion away from endplate
- Metabolized by pseudocholinesterase before it reaches site of action
- Two phases:
1. drug binds aggressively to ACh receptor, triggering depolarization at the motor endplate. Remains bound, so Na channels cannot depolarize.
2. after the drug has been bound for a while, induces conformational change–>nondepolarizing block that is irreversible
Succinylcholine uses
Temporary muscle paralysis in surgery and intubation
Succinylcholine side effects
-Cardiovascular: low dose-nagative chronotropic and inotropic effects
high dose-positive chronotropic and inotropic effects, raises catecholamine levels
-Fasciculations during phase 1 (visible motor unit contractions)
-Myalgia
-Hyperkalemia- especially concerning in setting of burns, trauma, spinal cord injury, cardiac disease and metabolic abnormalities
-Malignant hyperthermia
Nondepolarizing agent drug names
- Mivacurium (short acting)
- Vecuronium (intermediate acting)
- Rocuronium (intermediate acting)
- Atracurium (intermediate acting)
- Pancuronium (long acting)
- Doxacurium (long acting)
(obvious) NOTE: they all end in -curonium or -curium
Nondepolarizing agent mechanisms
- ACh receptor competitive antagonists
- Bind to ACh receptor, but does not cause depolarization and blocks ACh from binding
- Most depend on hepatic or renal elimination to terminate effect (exception=mivacurium which is metabolized by pseudocholinesterase and thus safe for pts with renal or hepatic disease
- Can give AChE inhibitor to reverse effects
Nondepolarizing agent uses
- Muscle relaxant during intubation, surgery
- Can be used in place of depolarizing agent
- Decreases the amount of required inhalational agents and helps maintain paralysis
Nondepolarizing agent side effects
- Respiratory failure secondary to diaphramatic paralysis
- Tachycardia (pancuronium)
- Histamine release (Mivacurium)
Cholinesterase inhibitor drug names
- Neostigmine
- Pyridostigmine
- Edrophonium
- Physostigmine
Cholinesterase inhibitor mechanism
- Inactivate AChE by electrostatic or covalent binding
- Prevents ACh degradation at the neuromuscular junction
Cholinesterase contraindications
-With depolarizing agents: by inhibiting cholinesterase and pseudocholinesterase, it prolongs the phase 1 block
Cholinesterase uses
- Reverse effects of nondepolarizing agents during surgery
- Used to diagnose (edrophonium) and treat (neostigmine) myasthenia gravis
Cholinesterase side effects
- Bradycardia
- Bronchospasm
- Excitation (physostigmine)
- Intestinal spasm
- Increased bladder tone
- Pupillary constriction
Anticholinergic drug names
- Atropine
- Scopolamine
- Benztropine
- Glycopyrrolate (charged and cannot cross the BBB)
Anticholinergic drug mechanism
-Complete block of ACh receptors
Anticholinergic uses
- Primary use: anesthesiology
- Scopolamine is antiemetic
- Atropine: generally used for cardiovascular effects (reverses vagal-stimulated bradycardia, decreases respiratory secretions, relaxes bronchial smooth muscle, reversal of antipsychotic extrapyramidal effects) or with pralidoxime for organophosphate poisoning
Anticholinergic side effects
-CNS stimulation
-Cutaneous blood vessel dilation
-Urinary retention
-Cycloplegia (paralysis of ciliary muscle–>blocks eye accommodation)
-Decreased secretions
Mnemonic: “blind as a bat, dry as a bone, red as a beet, mad as a hatter and hot as a hare”
Barbiturate drug names
-Phenobarbital
-Pentobarbital
-Thiopental
-methohexital
-Secobarbital
Obvious NOTE: all end in -tal
Barbiturate mechanism
-Increase duration of Cl channel opening on GABAa receptors–>enhanced GABAergic transmission
Mneumonic: “BarbiDURATe increases the DURATion of GABAa receptor Cl channel opening)
-Can block excitatory glutamate receptors
-CYP450 inducer
-Phenobarbital is 75% metabolized in the liver and 25% excreted unchanged by the kidney
Barbiturate uses
- Short term agents (thiopental, methohexital) used in anesthesia
- Tonic-clonic seizure prevention, status epilepticus, exlampsia (phenobarbital)
- Mild sedative
- Relieve anxiety
- Insomnia (but not recommended because suppresses REM sleep>other stages)
Barbiturate side effects
- Dependence
- Synergy with alcohol and benzodiazepines (cross-tolerance)
- Respiratory, cardiovascular and CNS depression that can cause coma or death
- CYP450 induction alters other drug metabolism
Barbiturate contraindications
-Acute intermittent porphyria (barbiturates activate ALA synthase, the rate-limiting enzyme of heme synthesis)
Treatment of barbiturate overdose
- Manage symptoms (ABCs)
- Hemodialysis in severe cases
- Alkalization of urine to help with elimination (phenobarbital)
Symptoms of barbiturate withdrawal
- Anxiety
- Irritability
- Elevated heart and respiration rate
- Muscle pain
- Nausea
- Tremors
- Hallucinations
- Confusion
- Seizures
- Death if untreated
Benzodiazepine drug names
-Diazepam
-Lorazepam
-Triazolam
-Temazepam
-Oxazepam
-Midazolam
-Chlordiazepoxide
Alprazolam
NOTE: most end in -zolam
Benzodiazepine mechanism
- Increased frequency of Cl channel opening with binding to GABA receptors
- Cl entry–>hyperpolarization which reduces excitability
- Effect terminated through redistribution and excretion (metabolized by hepatic microsomal system into active metabolites)
- Can cross the placental barrier
Benzodiazepine uses
- Anxiolytics via inhibition of lymbic circuit
- Muscle relaxant to treat spasms
- Amnesic agents for endoscopy
- Anticonvulsant
Short acting benzodiazepines
(Not great) Mnemonic: “TOM thumb”
- Triazolam
- Oxazepam
- Midazolam
Benzodiazepine side effects
- Synergistic with alcohol and barbiturates (cross-tolerance)
- Respiratory depression and coma (much less than barbiturates)
- Drowsiness/confusion
- Tolerance
- Dependence
- Decrease latency to sleep onset and increase stage 2 sleep. REM sleep and stages 3 and 4 sleep are decreased
Benzodiazepine competitive antagonist
Flumazenil
Benzodiazepine withdrawal
-Confusion
-Anxiety
-Agitation
-Restlessness
-Insomnia
-Tension
Note: similar to barbiturate withdrawal, but less severe
Opiod drug names
- Morphine
- Hydromorphine
- Oxymorphone
- Methadone
- Meperidine
- Fentanyl
- Sufentanil
- Alfentanil
- Remifentanil
- Codeine
- Hydrocodone
- Oxycodone
- Buprenorphine
Neuroleptics (definition)
- Classified as first generation and second generation (atypical) anti-psychotics
- Block type 2 dopamine receptors (D2)
- Most effective against the positive symptoms of schizophrenia (such as hallucinations and delusions)
First-generation anti-psychotics drug names
Low potency group -Chlorpromazine -Thioridazine High potency group -Haloperidol -Trifluoperazine -Pimozide -Perphenazine
Mechanism of first-generation anti-psychotics and difference between low and high potency drugs in this group
- All work in the mesolimbic system by blocking post-synaptic D2 receptors
- Low-potency drugs have an affinity for muscarinic ACh receptors, alpha-adrenergic receptors, and histaminergic receptors (note: this causes side effects)
- High potency drugs have a greater affinity for D2 receptors
Uses of first-generation anti-psychotic drugs
- Treatment of acute psychosis
- Treat of schizophrenia
- Treatment of bipolar disorder
- Haloperidol used in Tourette syndrome (to control tics) and Huntington disease (to control choreiform movements)
Side effects of first-generation anti-psychotic drugs
All 1st gen drugs:
- Neuroleptic malignant syndrome
- Hyperprolactinemia (amenorrhea, galactorrhea, gynecomastia)
High-potency anti-psychotics
- Extrapyramidal signs (Parkinsonism, akathisia, tremor)
- Movement disorders (tardive dyskinesia, dystonia)
Low-potency anti-psychotics
- Sedation
- -> *Blockade of histamine receptors causes weight gain, sedation, orthostatic hypotension, tremor, and sexual dysfunction
- Anticholinergic side effects
- -> *Blockade of muscarinic receptors causes facial flushing, dry mouth, urine retention, constipation
Thioridazine (additional side effects)
- Sudden death from prolongation of the QT interval, leading to torsades de points
- Irreversible retinal pigmentation
Chlorpromazine (additional side effects)
-Deposits in the lens and cornea
Second-generation (atypical) anti-psychotic drug names
-Clozapine
-Risperidone
-Olanzapine
-Quetiapine
-Ziprasidone
Aripiprazole
Mechanism of second-generation (atypical) anti-psychotic drugs
- Effects on the serotonergic, dopaminergic (with D2 affinity), and noradrenergic systems
- Each medication has a different neuroreceptor profile (leading to different therapeutic action and different side effects)
Advantages of second-generation (atypical) anti-psychotic drugs over first-generation anti-psychotic drugs
- Second-generation drugs are more effective with negative and chronic symptoms of schizophrenia (avolition, alogia, flattened affect)
- Second-generation drugs have a lower risk of tardive dyskinesia, neuroleptic malignant syndrome, and extra-pyramidal signs
Uses of second-generation (atypical) anti-psychotic drugs
- Treatment of schizophrenia
- Treatment of psychosis
- Treatment of bipolar disorder
- Risperidone used for antidepressant augmentation
Selective serotonin reuptake inhibitor side effects
- Few side effects, so safe in pregnancy
- Diarrhea
- Sexual dysfunction (decreased libido, erectile dysfunction, anorgasmia)
- Weight gain
- Fatigue
- Discontinuation syndrome (worse with short-acting): dizziness, vertigo, nausea, fatigue, headache, insomnia, shock-like sensations, paresthesia, visual disturbances, muscle pain, chills, irritability, agitation and suicidal thoughts
- Birth defects–most commonly ventral septal defects–can happen (greatest risk with paroxetine)
Monoamine oxidase inhibitor (MAOI) drug names
- Phenelzine
- Tranyleypromine
- Isocarboxazid
Opiod mechanism
- Analgesics that act on the CNS
- Endogenous endorphins are formulated from proopiomelanocortin (POMC), which is also the precursor for the formation of adrenocorticotropic hormone (ACTH), melanocyte-stimulating hormone (MSH) and lipotropin (LPH)
- Synthetic opiods structurally resemble endogenous opiods
- Most bind to the Mu-opiod receptor either as full or partial agonists
Opiod uses
- Local analgesia (regional nerve blocks, epidural nerve blocks, spinal nerve blocks)
- Systemic pain relief (patient controlled analgesia)
- Chronic pain management
- Used in antitussives (e.g. dextromethorphan)
Opiod side effects
- Tolerance
- Dependence
- Overdose potential
Buspirone mechanism
- Partial serotonin 1A agonist (5HT-1A) receptor agonist in the CNS
- Does not affect GABAergic receptors, so it does not interact with ethanol, is non-sedating and has low risk of dependence as it does not cause the euphoria associated with benzodiazepines and barbiturates
Buspirone uses
-Generalized anxiety disorder
Buspirone side effects
- May stimulate the locus ceruleus–>increased norepinephrine release–>increased anxiety
- May not work for patients with a history of benzodiazepine use or severe anxiety
Selective serotonin reuptake inhibitor drug names
- Citalopram
- Fluoxetine
- Paroxetine
- Sertraline
- Fluvoxamine
Selective serotonin reuptake inhibitor mechanism
- Prevent reuptake of serotonin by the presynaptic terminal–>increased availability of serotonin to the postsynaptic membrane
- Takes 3-6 weeks to get desired effect clinically
- Does not increase mood in non-depressed patients
Selective serotonin reuptake inhibitor uses
- First line for depressive and anxiety disorders
- Panic disorder
- obsessive-compulsive disorder
- Post-traumatic stress disorder
- Eating disorders
- Trichotillomania (impulsive hair eating)
- Prevents post-stroke depression and improves morbidity and mortality even in the absence of depression
Selective serotonin reuptake inhibitor side effects
- Few side effects, so safe in pregnancy
- Diarrhea
- Sexual dysfunction (decreased libido, erectile dysfunction, anorgasmia)
- Weight gain
- Fatigue
- Discontinuation syndrome (worse with short-acting)
- Birth defects can happen (greatest risk with paroxetine)
Monoamine oxidase inhibitor (MAOI) drug names
- Phenelzine
- Tranyleypromine
- Isocarboxazid
MAOI mechanism
- Irreversibly inhibits Monoamine oxidase-A from breaking down norepinephrine–>increased norepinephrine levels
- MAO-A also breaks down serotonin and tyramine, so there are increased levels of these neurotransmitters as well
MAOI side effects
Use with tyramine causes potentially fatal side effects and the following symptoms: -Hypertensive crisis -Diaphoresis -Headache -Vomiting MUST AVOID: cheese (pizza), Pepperoni, Beer, Wine, Smoked/pickle meat, Liver, Spoiled foods Use with SSRIs can cause serotonin syndrome: -Confusion -Hyperthermia -Myoclonus -diaphoresis -Hyperreflexia
Side effects of second-generation (atypical) anti-psychotics
All 2nd generation drugs:
- Cardiotoxicity
- Abnormal ECG
- Neuroleptic malignant syndrome
- Hyperprolactinemia (gynecomastia, galactorrhea, and amenorrhea)
- Extrapyramidal signs (Parkinsonism, akathisia, tremor)
- Increased chance of seizures
- Insulin intolerance, T2D (unrelated to weight gain)
- Hyperlipidemia
Clozapine (additional side effects)
- Agranulocytosis
- Weight gain
Olanzapine (additional side effects)
-Weight gain
Risperidone (additional side effects)
-Especially prone to hyperprolactinemia
Ziprasidone (additional side effects)
-Prolongation of QT and PR intervals
Note: Ziprasidone and aripiprazole have fewer metabolic side effects than other 2nd-generation drugs
Names of Mood Stabilizing Drugs
Lithium
Mechanisms of Mood Stabilizing Drugs (Lithium)
- Exact mechanism of lithium unknown
- It is believed that lithium interferes with monoamine synthesis, release, and reuptake
Uses of Mood Stabilizing Drugs (Lithium)
- Treatment of Bipolar Disorder
- Used to augment antidepressants in major depressive disorder
- May take 2-3 weeks for effects of lithium to manifest