Intro to Neuropsychopharmacology Part 1 Flashcards
Biogenic Amine Pathways in the Brain:
-
Neurons containing norepinephrine are located in the locus coeruleus
- innervate nearly every part of the CNS
-
Neurons containing serotonin are located in two groups of raphe nuclei
- project to most of the brain
- Neurons containing dopamine are located in the substantia nigra and the ventral tegmental area of the midbrain
-
Neurons containing ACh are located in the basal forebrain complex
- includes the septal nuclei and nucleus basalis
- project to the hippocampus and the neocortex
Dopamine pathways in the brain include:
- Nigrostriatal
- Tubero-infundibular
- Mesolimbic
- Mesocortical
- GABA localization:
- Limbic Structures:
- GABA Localization: Substantia Nigra, Globus Pallidus, Hippocampus
- Limbic structures: Amygdala, Hypothalamus, Spinal cord
AFFECTIVE DISORDERS:
- Major Depressive Disorder
- Unipolar
- Bipolar
- Dysthymic Disorder
- Mania
Monoamine Theory of Depression
Based on pharmacological evidence:
- the ability of known antidepressant drugs (TCAs and MAO inhibitors) to facilitate monaminergic transmission
- drugs such as reserpine that depletes amines to cause depression
- Other pharmacological evidence (ie. delay in onset of effects) fails to support the traditional monoamine hypothesis
- But, pharmacological manipulation of monoamine
transmission remains the most successful approach to treating depression
Neurochemical Effects of Tricyclic Antidepressants:
-
Blockade of transmitter uptake
- NE and 5–HT
- Receptors and second messengers
Drugs Used in the Treatment of Depressive Disorders:
- Serotonin Specific Reuptake Inhibitors – SSRIs
- Serotonin – Norepinephrine Reuptake inhibitors – SNRIs
- Atypical Antidepressants – Mirtazapine and Bupropion
- Monoamine Oxidase Inhibitors
SSRI:
Pharmacokinetics and metabolism
- Most commonly used anti-depressants
- Favored because of side effect profile
- Both long and short half-life compounds available
- Fluoxetine has a long half-life active metabolite
**SSRI: **
Pharmacological properties and side effects
- Antidepressant actions similar in efficacy and time- course to TCAs
-
Common side effects include:
- Nausea and vomiting
- Insomnia
- Nervousness
- Sexual dysfunction
- Acute toxicity is less than with TCAs and MAO inhibitors ⇒ Less risk of overdose
-
Serotonin reaction can occur in presence of MAO inhibitors
- Includes hyperthermia, muscle rigidity and cardiovascular collapse
- Black box warning for use in teens
- SSRI discontinuation syndrome
SSRI Discontinuation Syndrome:
- Symptoms occur within 1 to 7 days after stopping an SSRI
- Most common with shorter acting drugs like sertraline and fluvoxamine
- Not with fluoxetine
- Symptoms can include: dizziness, light-headedness, vertigo, anxiety, fatigue, headache, tremor, visual disturbances, etc.
SSRIs:
Clinical uses
Approved clinical uses include:
- Major depressive disorder
- Obsessive-Compulsive disorder
- Panic disorder
- Social phobia
- PTSD
- Generalized anxiety disorder
- PMS
- Hot flashes associated with menopause
SSRI Drugs (2):
- Fluoxetine
- Sertraline
Fluoxetine:
- First SSRI on market
- Effects on drug metabolism
-
Active metabolite with long half-life
- 7 days or more
- Available as sustained released product
- PMS
Sertraline:
- Similar in action to fluoxetine with less effects on drug metabolism
-
Shorter half-life
- OCD, PTSD, Panic attacks
SNRI drugs:
**Duloxetine **(Cymbalta®)
- 12-18 hour half-life
- Side effect profile is more SSRI-like than TCA-like
- Use with caution in patients with liver disease
- Also approved for use in fibromyalgia, diabetic neuropathy, back pain, and osteoarthritis pain
Atypical antidepressants:
- Drugs without typical tricyclic structure or SSRI action
- May or may not block catecholamine uptake
Atypical antidepressants drugs (2):
- Bupropion
- Mirtazapine
Bupropion:
- Weakly blocks norepinephrine and dopamine uptake
- Also approved for nicotine withdrawal and seasonal affective disorder
- No weight gain or sexual dysfunction
Mirtazapine:
- Blocks presynaptic alpha2 receptors in brain
- Increases appetite
- AIDS patients
Tricyclic Antidepressants:
- First highly effective drugs for the treatment of depression
- Block NE and 5-HT reuptake
- Now used secondarily to SSRIs and other newer compounds
Tricyclic Antidepressants:
Pharmacokinetics and Metabolism
- Rapidly absorbed after parenteral or oral administration
- Relatively high concentrations are found in the brain and heart
- Imipramine and amitriptyline are demethylated to active metabolites which are used as drugs by themselves
- Long plasma half-life: 8 to 100 hours
Tricyclic Antidepressants:
Pharmacological Properties and Side Effects
- Produces elevation of mood in depressed patients after about 2 to 3 weeks
- Decreases REM and increases stage 4 sleep
- Prominent anticholinergic effects
- Cardiac abnormalities
- Sedation
- Cardiac abnormalities
- **Overdoses: **acute toxicity
- Symptoms include hyperpyrexia, hyper- or hypotension, seizures, coma and cardiac conduction defects
Tricyclic Antidepressants:
Drug interactions
- Guanethidine - blocks guanethidine uptake
- Sympathomimetic drugs - particularly indirect acting ones
- Effects on absorption and metabolism of other drugs
Tricyclic Antidepressants:
Therapeutic uses
-
Treatment of major depression
- replaced by SSRIs as primary treatment
- Enuresis in childhood – Imipramine
- Chronic pain – amitriptyline
- Obsessive-compulsive disorders – clomipramine and SSRIs
- Other tricyclic antidepressants – amoxapine, desipramine, doxepin, nortriptyline
Monoamine Oxidase Inhibitors:
- Block the oxidative deamination of naturally occurring biogenic amines, such as NE, DA and 5-HT and ingested amines
- Monoamine oxidase is found in the mitochondrial fraction of neurons
- It is also found in liver, lung and other organs
-
Two forms of MAO - A and B
- Antidepressant action probably due to inhibition of MAO-A
Phenelzine:
irreversible inhibitor of MAO
Monoamine Oxidase Inhibitors:
- Pharmacological Properties:
- Drugs and Food Interaction:
- Therapeutic Use:
-
Pharmacological Properties:
- Antidepressant action takes about 2 weeks
- Produces mood elevation in depressed patients
- May progress to hypomania, particularly in bipolar disease.
- Acute toxicity can produce agitation, hallucinations, hyperpyrexia, convulsions and changes in blood pressure
-
Drugs and Food Interaction:
- Tyramine from food ⇒ can produce
- *hypertensive crisis**
-
Therapeutic Use:
-
Major depression
- not drug of first choice
-
Major depression
Psychosis:
- A general term for major mental disorders characterized by:
- derangement of personality
- loss of contact with reality
- delusions
- hallucinations
- prototype is Schizophrenia
Etiology of Schizophrenia:
- cause(s) of schizophrenia are yet unknown
-
DOPAMINE HYPOTHESIS:
-
Schizophrenia results from hyperactivity of
dopaminergic neurons or their receptors,
particularly those with terminals in limbic areas
of the brain
-
Schizophrenia results from hyperactivity of
What do all anti-psychotic drugs interact with?
dopamine systems
Dopamine receptors:
- D1 type (D 1 and D 5) – Activate adenylyl cyclase
- D2 type (D 2, D 3, D 4) – Inhibit adenylyl cyclase
- Autoreceptors
Which receptors do atypical antipsychotic drugs target?
DA + 5HT2 receptors
Treatment of schizophrenia:
- drug treatment is the most common effective therapy
- it is not curative
Actions of Antipsychotic Drugs:
-
Decrease in psychotic behavior - drugs differ only in potency
- All symptoms of schizophrenia are not equally well treated
- exception Clozapine and other atypical drugs
- Sedation
-
Extrapyramidal actions - result of dopamine receptor blockade
- Include, Dystonias Parkinsonism and Akathisia
- Long-term treatment ⇒ Tardive dyskinesia –
- Oral-facial dyskinesias, choreoathetoid movements
- Neuroendocrine effects - result of dopamine receptor blockade
- Orthostatic hypotension - alpha adrenergic receptor blockade
- Weight gain - Diabetes related events are more common with atypicals, particularly olanzapine, risperidone, clozapine and quetiapine.
-
Neuroleptic malignant syndrome – Fever, mutism, EPS, possible death
- Treatment includes cooling and hydration,
bromocriptine and dantrolene
- Treatment includes cooling and hydration,
Prototype available typical antipsychotic drugs classes (2):
- Phenothiazines
- Butyrophenone Derivative
- *Phenothiazines**
- (3):**
- Chlorpromazine
- Thioridazine
- Fluphenazine
- *Chlorpromazine**
- *:**
aliphatic side chain
- low to medium potency
- sedative
- pronounced anticholinergic actions
Thioridazine:
**piperidine side chain **
- low potency
- sedative
- less extrapyramidal actions
- anticholinergic
Fluphenazine:
piperazine side chain
- high potency
- less sedative
- less anticholinergic
- more extrapyramidal reactions
Haloperidol:
Butyrophenone Derivative
- not chemically related to the phenothiazines but is pharmacologically similar to the high potency piperazine derivatives
Atypical Antipsychotic Agents (5):
- Clozapine
- Olanzapine
- Risperidone
- Quetiapine
- Aripiprazole
Atypical Antipsychotic Agents:
Uses
- Acute psychotic episodes
- Chronic schizophrenia
- Manic episodes, bipolar disorder
- aripiprazole, olanzapine, quetiapine, ziprasidone, risperidone, asenapine, lurasidone
-
Augmentation of antidepressant action:
- aripiprazole, olanzapine, quetiapine
- Tourette’s syndrome
- Antiemesis – not thioridazine
Clozapine:
- Blocks D4 and 5-HT2 receptors
- Little effect on D2
- Muscarinic antagonist
- Less extrapyramidal symptoms
- May cause serious agranulocytosis or other blood dyscrasias in a small percentage of patients
- Weight gain
- Improves negative symptoms
Olanzapine:
- Related to clozapine
-
More potent as 5-HT2 antagonist
- D1 and 2 antagonist, some D4
- Few extra pyramidal symptoms
- No agranulocytosis
- Weight gain and diabetes risk
- Less seizure incidence than clozapine
- Reports of olanzapine abuse
Risperidone:
- Combined dopamine and serotonin receptor antagonist
- Has a low incidence of extrapyramidal side effects
- Greater reduction in negative symptoms
- Less seizure activity and less antimuscarinic than
clozapine - Paliperidone (Invega®) is the active metabolite of risperidone
- Both are also available as intramuscular depot preparations
Quetiapine:
- Structurally related to clozapine with **effects on D2 and 5-HT2 receptors **
- Similar to risperidone and olanzapine in effects on schizophrenia symptoms and side effects
- Approved for augmentation in depression
- Has some abuse potential
**Aripiprazole (Abilify®): **
- D2 partial agonist and 5-HT2 antagonist
- adjunct in the treatment of depression