Lecture 18: Antidepressants Flashcards
dysthymia
relatively mild but prolonged symptoms that persist for at least two years
depression is the ___ most disabling disease in the world
4th
by 2020, depression will be the ___ leading cause of disability
2nd
WHO estimated that ___ people worldwide have depression
300,000,000
MDD responsible for __% of psychiatric hospitalizations
70
MDD responsible for __% of suicides
40
__ of the US population suffers per year
9-10%
__% of men and __% of women experience depression
10, 25
__% of cases are adequately treated per year
21
MDD is __ more common in 1st degree relatives of someone with depression
3x
classically, MDD was thought to be caused by ___
deficiency in monoamines (5HT, DA, NE)
problem with monoamine deficiency hypothesis
NT changes occur shortly after taking antidep, but clinical benefits develop slowly
now, interest is on long term action, specifically ___
2nd messengers and their fx
3 possible 2nd messenger effects
- protect neurons from damage due to injury or trauma
- promote and maintain health and stability of new neurons
- promote activity-dependent remodeling of existing cells; plasticity
neurogenic theory of depression; 2 discoveries
- neurons are able to repair/remodel themselves
2. adult brain can make new neurons
postnatal neurogenesis
brain making new neurons as an adult
stressful conditions can damage the ___
hippocampus
hippocampus shrinks in response to ___
corticosteroids
depression is now thought of as a ___
neurodegenerative disorder
stressful conditions reduce neurogenesis in __ (2)
hippocampus
frontal cortex
network hypothesis of antidepressants
recovery from depression is gradual process facilitated by structural guidance and rehab
2 possible pathways for antidep MoA starting with 5HT or NE reuptake inhibition
- 5HT4,6,7 / beta adrenergic - adenylyl cyclase - cAMP - cAMP dep protein kinase (PKA) - increase creb (cAMP response element binding protein) - BDNF (brain derived neurotrophic factor)
- 5HT2 / alpha1 adrenergic - Ca2+ dep kinases - CREB - BDNF
BDNF
brain-derived neurotrophic factor
CREB
cAMP response element-binding protein
PKA
cAMP-dependent protein kinase
what increases expression of adenylyl cyclase?
stimulation of 5HT4,6,7 or beta adrenergic
what increases expression of Ca2+ dependent kinases?
stim of 5HT2 or a1 adrenergic
adenylyl cyclase increases __
cAMP
cAMP increases ___
PKA
PKA increases ___
CREB
CREB increases __
BDNF
what does BDNF do? (3)
- trophic actions
- increased function
- synaptic remodeling
chronic stress decreases the expression of __ in the ___
BDNF, hippocampus
stress elevates levels of ___
glucocorticoids
what do glucocorticoids do?
reduce expression of BDNF
what does reduced expression of BDNF do?
atrophy or death or neurons
6 types of AD
- tricyclic
- MAOI
- atypical
- SSRIs
- dual action
- SNRIs
1st generation ADs
TCAs, MAOIs
1st TCA
imipramine
imipramine MoA
blocks presyn transporters for 5HT and NE
general TCA action
blocks presyn transporters for 5HT and NE
what were TCAs named for?
their structure
monoamine hypothesis of mania and depression
depression from deficiency of NE and 5HT; excess leads to mania
MAOI mech of action
block enzyme MAO that metabolizes and regulates amount of amine transmitters in nerve terminal
difference between MAOI and TCAs
TCAs inhibit reuptake, MAOIs inhibit degradation
3 TCA clinical limitations
- slow onset
- side effects
- cardiotoxic/overdose fatality
3 second gen compounds
- trazodone (desyrel)
- bupropion (wellbutrin)
- venlafaxine (effexor)
4 TCAs
- imipramine (tofranil)
- desipramine (norpramin)
- nortriptyline (pamelor, aventil)
- clomipramine (anafranil)
when were SSRIs invented?
1980s-1990s
first SSRI
prozac
has availability of SSRIs reduced the number of treatment resistant patients?
no
are SSRIs more efficacious?
no, but fewer side effects
6 SSRIs
- fluoxetine (prozac)
- sertraline (zoloft)
- paroxetine (paxil)
- citalopram (celexa)
- fluvoxamine (luvox)
- escitalopram (lexapro)
when were TCAs and MAOIs introduced?
1950s-1960s
prototypic TCA
imipramine (tofranil)
pharmacologically active metabolite of imipramine
desipramine (norpramin)
2 MoAs of imipramine/desipramine
- block presyn reuptake transporter for 5HT and NE
2. block postsynaptic receptors for histamine, ACh, and NE (alpha adrenergic)
blockade of histamine receptors results in ___
drowsiness/sedation
blockade of AChRs results in (6)
- confusion
- memory and cognitive impairments
- dry mouth
- blurred vision
- increased HR
- urinary retention
blockade of NE receptors results in ___
fx blood pressure, can cause orthostatic hypertension
nortriptyline and desipramine have ___ than other TCAs
less sedation and fewer anticholinergic side fx
half life of imipramine
10-20h
3 TCAs other than imipramine
- desipramine (norpramin)
- nortriptyline (pamelor, aventil)
- clomapramine (anafranil)
4 limitations of TCAs
- slow onset
- side fx
- cardiotoxic arrhythmias
- non universal efficacy
surprisingly, TCAs can be effective ___
analgesics
MAO effect on GI tract
breaks down tyramine
effect of elevated tyramine
increase blood pressure, possible heart attack/stroke
trazodone was __ second gen
3rd
most common trazodone side effect
drowsiness
trazodone MoA
not very potent 5HT and NE reuptake blocker
trazodone effect on sex
may improve sex, but has risk of priapism
trazodone has ___ half life
short
clomipramine (anafranil) is structurally similar to ___, but has greater effect on __
TCAs; more 5HT reuptake effect
clomipramine and its active metabolite also inhibit ___
NE
clomipramine is classified as a ___
mixed serotonin-NE reuptake inhibitor
MoA of SSRIs
block presynaptic transporter for 5HT
___ is least selective for 5HT, and ___ is most selective
prozac, celexa
which receptor is the basis of therapeutic effect of all SSRIs?
5HT1
stimulation of 5HT2 receptors thought to be responsible for (5)
- insomnia
- anxiety
- agitation
- sexual dysfunction
- serotonin syndrome
2 effects at 5HT1
antidepressant, anxiolytic
effect at 5HT3
nausea
are SSRIs fatal in OD?
no
SSRIs can inhibit ___, causing what dangerous result?
CYP450
possibly dangerous reactions with other meds
5 concerns with SSRIs
- serotonin syndrome
- withdrawal
- sexual dysfunction
- long term may cause cog impairment
- fetal effects
serotonin syndrome (5)
- cog disturbance (confusion, hypomania)
- agitation/restlessness
- autonomic dysfunction (fever, diarrhea, tachycardia)
- neuromuscular impairment (ataxia, twitching)
- visual hallucinations
what percent of patients develop SSRI withdrawal?
60%
6 core fx of withdrawal from SSRIs
- flulike symptoms
- nausea
- insomnia
- imbalance
- sensory disturbances (shocks)
- hyperarousal
___% of depression patients with SSRIs experience sexual dysfunction
80%
5 other side fx of SSRIs
- suicidality
- sleep disturbance
- apathy
- physiological symptoms (nausea, coma, muscle cramps, GI bleeding)
- pregnancy warning
drug most associated with serotonin syndrome, psychosis, temper, delusions, discontinuation
paxil
fluvoxamine (luvox) sturctural derivative of ___
prozac
large dose of citalopram associated with ___
ECG irregularities, seizures
which drug causes problems for liver? which causes least problems?
prozac
celexa
escitalopram is the ___ of celexa
therapeutically active optical isomer of celexa
lexapro is __ as potent as celexa
2x
first dual-action antidep
TCAs
venlafaxine MoA
mixed 5HT-NE reuptake inhibitor
duloxetine/cymbalta MoA
blocks reuptake of 5HT and NE
mirtazepine (remeron) MoA
increases presyn release of NE and 5HT
- blocks central alpha2 autoreceptors, increasing NE
- blocks adrenergic heteroreceptors located on 5HT neuron terminals, which usu inhibit 5HT release (only 5HT1 receptors, because mirtazepine blocks 5HT2 and 5HT3)
problem with remeron
causes drowsiness bc of action on histamine; appetite increase/weight gain
MoA bupropion
dopamine-norepinephrine reuptake inhibitor
are SNRIs better than placebo?
no
STAR*D study
sequenced treatment alt to releive depression
results of STAR*D
zoloft and escitalopram may have slight advantages, though modest benefits over others
combinations of ___ and ___ are being explored.
combo of SSRI and 5HT2 receptor antagonist
ketamine MoA
NMDAR antagonist
3 benefits of ketamine
- response in hours
- promotes synaptogenesis
- effective in 70% of patients
problem with ketamine
best route is IV
novel approach to depression
effort to manipulate hypothalamic-pituitary-adrenal (HPA) axis