MEDI7111 Lecture Notes - Lecture 16: General Anaesthesia, Hypoventilation, Pharmacokinetics
Therapeutics
Antidepressant Drugs
All antidepressant drugs take 2-3 weeks to take effect, during which time they may actually
enhance the disease process which increases the risk of suicide during this time (particularly in
adolescents). However the biological effects of the drugs given is relatively unknown.
When deciding what drug to give, SSRIs are the first line drug in adults as they have the most
favourable risk-benefit profile. Although all of the drugs have equal efficacy in clinical trials,
there are massive differences in responses patient to patient therefore a number of drugs may
need to be trialled before a drug that works well is found.
Drug Class Examples MOA Actions/Indication
s
Side Effects
Tricyclic
Antidepressants
N/A Inhibit the reuptake of
serotonin and NA into
the presynaptic
neuron
Non-specific drugs:
act on muscarinic,
histamine &
adrenoreceptors too
Only used for
refractory illness or
if working fine from
previous Dr’s script
Enhances serotonin
& NA signalling
Sedation (H1)
Postural
hypotension (α-1)
Blurred vision, dry
mouth,
constipation,
tachycardia (M1)
Selective
Serotonin
Reuptake
Inhibitors
(SSRIs)
Fluoxetine (Prozac)
Sertraline (Zoloft)
Escitalopram
(Lexapro)
Block the re-uptake of
serotonin into the
presynaptic neuron
Slow degradation of
intracellular serotonin
Usually 1st line
Enhances serotonin
signalling
Similar to TCAs but
less dramatic:
Weight gain,
insomnia, tremors,
dizziness etc.
Serotonin &
Noradrenaline
Reuptake
Inhibitors
(SNRIs)
Venlafaxine (Effexor)
Duloxetine
(Cymbalta)
Inhibits reuptake of
serotonin & NA but is
more specific than
TCAs
Can be 1st line if no
HTN or suicidal
ideation
Reduced relapse rate
compared to SSRIs
Similar to SSRIs
plus:
Hypertension
suicide risk ↑
Monoamine
Oxidase
Inhibitors
MAOIs
Selegilene (Emsam) Non-selective,
irreversible inhibition
of MOA (covalently
binds)
Not really used
Prevents
degradation of NA,
serotonin & DA
Patients on MOAIs
must have a
tyramine free diet
Unable to
metabolise dietary
tyramine (causes
malignant
hypertension)
Mixed Action
Antidepressants
NA-DA Reuptake
Inhibitors (DNRIs)
NA & specific
serotonergic
Blocks α-2, 5-HT2&3
and H1 receptors
Enhances signalling of
5-HT1
Less sexual
dysfunction &
insomnia compared
to SSRIs
More weight gain
compared to SSRIs
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Document Summary
All antidepressant drugs take 2-3 weeks to take effect, during which time they may actually enhance the disease process which increases the risk of suicide during this time (particularly in adolescents). However the biological effects of the drugs given is relatively unknown. When deciding what drug to give, ssris are the first line drug in adults as they have the most favourable risk-benefit profile. Although all of the drugs have equal efficacy in clinical trials, there are massive differences in responses patient to patient therefore a number of drugs may need to be trialled before a drug that works well is found. Inhibit the reuptake of serotonin and na into the presynaptic neuron. Only used for refractory illness or if working fine from previous dr"s script. Non-specific drugs: act on muscarinic, histamine & adrenoreceptors too. Block the re-uptake of serotonin into the presynaptic neuron. Inhibits reuptake of serotonin & na but is more specific than.
