Antidepressants and Lithium Flashcards
Fluoxetine
- SSRI
- potent inhibitors of CYP2D6 (drug interactions)
- metabolite norfluoxetine has LONG half-life of 7 to 9 days
Paroxetine
- SSRI
- potent inhibitors of CYP2D6 (drug interactions)
Sertraline
SSRI
Citalopram
SSRI
Escitalopram
SSRI
Fluvoxamine
- SSRI
- treatment of OCD
Venlafaxine
- SNRI
- extensively metabolized via CYP2D6
Duloxetine
SNRI
Imipramine
- Tricyclics (TCAs)
- more selective for serotonin transporter
Amitriptyline
TCA
Clomipramine
- Tricyclics (TCAs)
- treatment of OCD
Desipramine
- Tricyclics (TCAs)
- more selective for NE transporter
Nortriptyline
TCA
Trazodone
- 5-HT2 Antagonist
- LSD is an agonist
- prodrug that is converted to 5-HT2A antagonist
Mirtazapine
- 5-HT2 Antagonist
- antagonist of presynaptic alpha2 autoreceptor, enhances release of NE and 5-HT
- acts strongly on H1 receptor, so we can use this medication as a sedative
Bupropion
- class all by itself
- enhances both NE and DA neurotransmission
- inhibits reuptake transporters for both NE and DA as well (VMAT2)
- useful for smoking cessation
Phenelzine
- MAOI
- a hydrazide that combines irreversibly with MAO to provide long-lasting inhibition (covalent modification)
Tranycypromine
- MAOI
- does not bind irreversibly, but still has prolonged effect
Reserpine
- medication for high BP
- blocks the ability of the neurotransmitter to be concentrated in the vesicle and then causes the neurotransmitter to not be released and induces depression in the individual
- anti-psychotic
Block reuptake of neurotransmitters
- TCAs
- SNRIs
- SSRIs
Block breakdown of neurotransmitters
MAOIs
Limitation of Monoamine Hypothesis
- clinically useful antidepressants act rapidly at pharmacologic sites of action, yet clinical effects require 3 or more weeks of therapy
- while reserpine rapidly depletes neurotransmitter, several weeks of treatment are required to induce depression
Possible explanation for delay in clinical effect
- desensitization of presynaptic autoreceptors
- control in part the synthesis and release of neurotransmitters
- because the autoreceptor binds the same neurotransmitter that cell is releasing
- in short term you have an increase in the neurotransmitter in the synaptic cleft and may limit the amount of neurotransmitter released
- but then the autoreceptors become desensitized and the cell down-regulates the number of receptors and the hypothesis is that over long term treatment you lose the inhibition of control and release and then you release additional serotonin or norepinephrine
Serotonin Synthesis and Catabolism
- synthesized from tryptophan
- present in high concentrations in platelets and GI tract
- lesser amounts in brain and retina
Amphetamine
- inhibitor of monoamine storage
- substrate of reuptake transporter
- inside the cell it inhibits the transporter that reserpine inhibits, so when transporter is blocked you get a build up of neurotransmitter in the cell cytoplasm and then the excess of neurotransmitter in the nerve terminal causes the system to reverse and causes norepinephrine to release
- net result is that amphetamine causes a decreased release of vesicular transport and an increased release of non-vesicular transport
SSRI
- selective serotonin reuptake inhibitors
- inhibit 5-HT reuptake selectively as compared to NE reuptake
- relatively selective for 5-HT transporter, thus side effects limited to effects on 5-HT mediated responses
SNRI
- serotonin-norepinephrine reuptake inhibitor
- inhibit reuptake transporters for both NE and 5-HT
- TCAs also fall into this category, but are less selective
MAOI
- inhibitor of monoamine degradation
- monoamine oxidase (MAO) metabolizes monoamines
- phenelzie is a hydrazide that combines irreversibly with MAO to provide long-lasting inhibition (covalent modification)
- tranylcypromine does not bind irreversibly, but still has prolonged effect
MAOI drug interactions
- individuals taking MAOIs must be very wary of intake of tyramine
- at high levels, tyramine can reverse reuptake transporters (as amphetamines) causing uncontrolled catecholamine release and possible hypertensive crisis