1- Antidepressants Flashcards
What are the hypotheses for the cause of depression and which is the most relevant?
Monoamine (most relevant)- all antidepressants increase amine neurotransmission
(others: neurotrophic, neuroendocrine
How long does it take for antidepressants to have an effect?
2-3 weeks due to neuronal plasticity
(reuptake inhibited immediately but effects are delayed)
What is the long-term effect of uptake inhibitors?
Antidepressants down-regulate auto-receptors, increasing firing rate of 5-HT neuron
Antipressants only have effects if what?
Pt has chemical imbalances
What is the general MOA for TCAs?
Inhibit re-uptake of NE and 5-HT, block alpha-adrenergic, histamine, and muscarinic receptors
What is the use of TCAs?
Depression (one of last line), neuropathic pain, enuresis (smaller dose)
TCAs are typically well absorbed where and how often are they given?
Well absorbed orally, given 1x daily @ bedtime
What metabolizes TCAs?
CYP2D6 (drug interactions VERY common)
TCAs + MAOIs has the potential to cause what drug interaction?
Serotonin syndrome (severe CNS toxicity)
How do TCAs interact with SSRIs?
Compete for metabolism so can be toxic
How do TCAs interact with amphetamine (sympathomimetic drugs)?
Cause HTN
How do TCAs interact with alcohol or other CNS depressants?
Sedative actions
TCAs can potentiate the effects of what drug class?
Anticholinergic
Some of the SEs of TCAs include blockade of what receptors leading to what sxs?
- Histamine receptor blockade: drowsiness, sedation,
- Cholinergic blockade (PNS): dry mouth, urinary retention, impaired memory
- 𝜶1 receptor blockade: CV
Aside from receptor blockades, what are the other SEs of TCAs?
Weight gain, analgesia, SIADH, sexual dysfunction, decrease is seizure threshold, tolerance
What is the most serious complication a/w toxicity/ overdose of TCAs?
Cardiac toxicity (Torsades de pointes)
Aside from cardiac toxicity, what are other effects of toxicity/ overdose with TCAs?
Prolonged QT interval, cardiac arrhythmias, respiratory depression
(can be fatal)
Pt presents with toxicity/ overdose with TCAs. What is the tx for the Torsades de pointes?
Magnesium, isoproterenol, cardiac pacing
Pt presents with toxicity/ overdose with TCAs. What is the tx for managing arrhythmias/ preventing seizures?
Lidocaine, propranolol, phenytoin
Pt presents with toxicity/ overdose with TCAs. What is the tx for restoring acid/ base balance?
Sodium bicarb and potassium chloride
Can TCAs be given in pregnancy?
YES
Why is there limited use with TCAs?
Toxicity and potential overdose
How are TCAs dosed?
Start @ low dose then increase → tapered gradually
What is the benefit of using TCAs?
No euphoria/ low abuse potential
Due to the fact that all TCAs are equally effective at treating depression, choice of drug is based on what?
Adverse effects
Are Amitriptyline and Imipramine secondary or tertiary amines?
Tertiary (serotonin > NE)
What is the MOA of Amitriptyline and Imipramine and are they more or less potent than secondary amines?
Inhibit 5-HT reuptake
Produce more seizures and more sedating than secondary amines
Are Nortriptyline and Desipramine tertiary or secondary amines?
Secondary (NE > serotonin)
What is the MOA for Nortriptyline and Desipramine?
Block NE reuptake
What is the MOA for SSRIs?
Selectively inhibits 5-HT reuptake
What is the use for SSRIs?
Depression (DOC), panic disorder, OCD, social anxiety, bulimia, alcoholism, used in children/ teenagers
What is the DOC (class) for depression)
SSRIs
Where are SSRIs well absorbed and what is their half life?
Well absorbed by gut, t1/2 = 24-72hrs
What metabolizes SSRIs?
Metabolized by and inhibit CYP450s (2D6) = many drug interactions
What is the result of inhibition of CYP3A4 and CYP2D6 with SSRIs?
Increased toxicity of TCAs and Phenytoin/ carbamazepine
How do SSRIs interact with MAOIs?
Serotonin syndrome
How do SSRIs interact with St Johns wort or amphetamines?
Serotonin syndrome
How do SSRIs interact with beta blockers?
Heart block and hypotension
How do SSRIs interact with codeine?
Fluoxetine inhibits conversion to active compound
How do SSRIs interact with Meperidine?
Increases 5-HT (potential for serotonin syndrome)
How do SSRIs interact with Tramadol?
Increased seizure risk
What are the SEs (although mild) of SSRIs?
CNS stimulation, sexual disinterest/ dysfunction, photosensitivity
Amitriptyline and Imipramine drug class?
TCAs
Nortriptyline and Desipramine drug class?
TCAs
Fluoxetine drug class?
SSRIs
Sertraline drug class?
SSRIs
Paroxetine drug class?
SSRIs
Citalopram drug class?
SSRIs
Escitalopram drug class?
SSRIs
What is the DOC for depression?
Citalopram
What is the use of Paroxetine?
OCD and social anxiety
T1/2 of Sertraline is how long and what is important about its elimination?
26 hours, extensive first pass metabolism
What drug in the SSRI class has the fewest drug interactions?
Sertraline
What SSRI is preferred in elderly?
Sertraline
Does Fluoxetine or Norfluoxetine (active metabolite of Fluoxetine) have a longer half life?
Fluoxetine = 2-3 days
Norfluoxetine = 7-9 days)
What SSRI is most likely to inhibit CYP450 enzymes (CYP2D6)/ has the most drug interactions (ex. pain meds)?
Fluoxetine
Use of Fluoxetine should be cautioned in what patient population?
Diabetic pts (impairs blood glucose levels)
Venlafaxine drug class?
SNRIs
Duloxetine drug class?
SNRIs
What is the MOA for MAOIs?
Irreversibly inhibi MAOs (which metabolize NE, DA, 5-HT)
MAO-A metabolizes what and where (location)?
NE, DA, and 5-HT in both CNS and periphery
MAO-B metabolizes what and where (location)?
Selectively metabolizes DA in CNS but NOT in GI tract
What is the use of MAOIs?
Refractory depression (class of last choice)
What is the half life of MAOIs?
Long (effects persist after discontinuing drug)
How do MAOIs interact with sympathomimetic amines?
Severe hypertension (OTC cold/ cough meds)
How do MAOIs interact with any other drug that releases serotonin?
Serotonin syndrome → hyperpyrexia
What do MAOIs inhibit?
CYP450 enzymes (2D6)
What are the SEs of MAOIs?
- Hypertensive crisis (phenelzine), avoid foods w/ tyramine
- Orthostatic hypotension
- Weight gain (very common)
- Anticholinergic
Phenelzine drug class?
MAOIs
Selegiline drug class?
MAOIs
What is the MOA of Phenelzine?
Inhibits both MAO-A and MAO-B → increases NE and 5-HT
What is true about the drug action of Phenelzine?
Actions persist longer than serum levels
Phenelzine is a substrate for what?
MAOs
What is the use of Phenelzine?
Refractory depression (drug of last choice due to serious SEs)
What is the MOA of Selegiline?
Selectively inhibits MAO-B → increases DA
What is true about the SEs of Selegiline?
Fewer than other MAOIs
In addition to depression, Selegiline can also be used for what?
Parkinson’s (lower dose)
What is the MOA of Bupropion?
Inhibits DA reuptake
What is the use of Bupropion?
ADHD, alcoholism (decreases craving), ER for smoking cessation
What are the pharmacokinetics of Bupropion?
Extensive first pass metabolism, high protein binding, active metabolites
What are the SEs of Bupropion?
Seizures, CNS effects, cardiac
What is the MOA of Mirtazapine?
Blocks presynaptic alpha-2 receptors → increases release of NE and 5-HT
What is the use for Mirtazapine?
Eliminates SEs a/w SSRIs (anxiety, insomnia, nausea, sexual dysfunction)
What are the pharmacokinetics of Mirtazapine?
Metabolized by CYP450s, t1/2 = 20-40 hrs
What are the SEs of Mirtazapine?
Drowsiness/ sedation (may be advantage in depressed pts with insomnia and anxiety?
What is the MOA of Atomoxetine?
Selective inhibitor of NE reuptake
What is the use of Atomoxetine?
ADHD (first non-stimulant for tx), increase memory and attention
Does not cause euphoria = good choice for addicts
What are the SEs of Atomoxetine?
GI distress, insomnia, liver damage (possible but rare)
What is the MOA for Trazodone?
5-HT2A receptor antagonist
What is the use of Trazodone?
Sleep aid, pain management
What are the pharmacokinetics of Trazodone?
Short t1/2, high first pass metabolism
What are the SEs of Trazodone?
Sedating (not good antidepressant), priapism (rare but serious)