Psychiatric Medication - antidepressants Flashcards
(41 cards)
1
Q
What receptors can antipsychotics also act on?
A
- Dopamine
- Serotonin
- Muscarinic
- Adrenergic
2
Q
Receptor effects of noradrenaline
A
- Sweating
- Tremor
- Headaches
- Nausea
- Dizziness
3
Q
Common receptor effects on muscarinic
A
- Dry mouth - difficulty swallowing, thirst
- Difficulty urinating/urinary retention
- Hot and flushed skin
- Dry skin
4
Q
Effects on histamine receptors
A
- Dry mouth
- Drowsiness
- Dizziness
- Nausea and vomitting
5
Q
Where do most anti-depressants work?
A
- Serotonin activity, aim to increase activity at post synaptic receptors
- Often work for low mood and anxiety
6
Q
How quickly do antidepressants work?
A
Two to three weeks - always hold out for 4 weeks to check if response
7
Q
Most common types of antidepressants
A
- SSRI
- SNRI
- Mirtazapine
- Tricyclics
- MAOIs
8
Q
Antidepressant dose anxiety vs depression
A
- Anxiety (especially OCD) may need higher doses before giving up on the medication and trying a new one
- Depression can see effects at lower doses
9
Q
SSRI MOA
A
- Increase serotonin activity by reducing the pre-synaptic reuptake of serotonin (serotonin usually binds to pre-synaptic membrane and induces reuptake, if we put something on that receptor that has no action and doesn’t let serotonin bind = less reuptake)
- = more serotonin sits in synapse
- = downregulation of serotonin receptors on post synaptic membrane
10
Q
Common side effects of SSRI
A
- Sense restlessness, agitation on initiation (countered by use of benzodiazepines)
- Nausea/GI disturbance
- Headache
- Weight changes - usually suppresses appetite
- Sexual dysfunction - difficulty to achieve arousal and orgasm (SNRIs too)
- Bleeding and suicidal ideation - age related
11
Q
Why do SSRIs increase risk of bleeding?
A
- Serotonin receptors are on platelets
- = affects their ability to clot
- if previous bleeding history risk factor (eg NSAID or clotting problem) need cover with PPI
12
Q
Why can suicidal ideation increase with SSRI?
A
- Chemically raise serotonin
- = more motivated and energised but outlook on life is still the same –> sometimes gives enough energy to commit suicide
- Need to review at 3 weeks after taking to ask about suicide
- Older and younger men most at risk
13
Q
Most common SSRI and things to think about
A
- Sertraline (50-200mg) - safest in cardiac disease (minimum suggested by some sources 100mg) - significant risk of depression post heart attack
- Citalopram (20-40mg)/Escitalopram (10-20mg) - watch out for QTc prolongation - check for other QT prolonging drugs, do ECG couple months after starting
- Fluoxetine (20-60mg) - watch out for serotonin syndrome when switching - very long half life
- Paroxetine (20-60mg) - watch out for discontinuation syndrome - very short half life
14
Q
SNRI MOA
A
- Work same as SSRI but bind to noradrenaline reuptake receptors too
- Evidence based for neuropathic pain - duloxetine
- Very selective - well tolerated (like SSRI)
15
Q
Side effects for SNRI
A
- Similar to SSRI
- Greater potential for sedation, nausea and sexual dysfunction
- Can lead to increase in BP when get to 200mg or more
16
Q
What does it mean when a drug is ‘licensed’ for something?
A
- In BNF - listed as indication
- Are allowed to advertise drug that it has that function
- Drugs tend to get license within first few years so they can make money while still patented
17
Q
Examples of SNRIs
A
- Duloxetine - low dose range
- Venlafaxine - greater efficacy and can go to higher dose, caution in higher doses with heart disease. Monitor BP doses above 225mgs
18
Q
Mirtazapine MOA
A
- Recognised as class of its own
- Acts as a 5HT-2 and 5HT-3 antagonist
- Also works on adrenergic pathway - alpha agonist
- Very strong (H1) histamine activity - sedation - saturates receptors at low dose (low doses same histaminic burden as higher doses, reducing dose may not reduce side effect)
19
Q
Major side effects Mirtazapine
A
- Sedation - can be used to advantage
- Weight gain - can be used to advantage
20
Q
Tricylic antidepressants - when used
A
- If not responded to SSRI
- Newer ones (lofepramine and nortriptyline) are tolerated better than older (amitryptyline)
- Low doses used for neuropathic pain (but higher doses used for antidepressant MOA)
21
Q
Side effects of TCAs
A
- Muscarinic side effects
- Histaminic side effects
- Fatal in overdose - cause QTc prolongation and arrhythmias (torsade de pointes)
22
Q
Monoamine oxidase inhibitors MOA
A
- MAOI A - work more on serotonin
- MAOI B - work more on dopamine
- More effective on atypical depression
23
Q
Atypical depression - what is it?
A
- Sleep a lot more
- Eating lots and bad foods
24
Q
MAOI danger
A
- Dangerous interation with other drugs
- Potential for tyramine reaction –> hypertensive crisis (avoid tyramine rich foods eg cheese, pickled meats, wine)
- If changing another antidepressant need a washout period (long half life, don’t start anything for 6 weeks)
25
Examples of MOAIs
* Irreversible more dangerous - Phenelzine, Isocarboxazid
* Reversible less dangerous - Moclobemide, Tranylcypromine
26
Vortioxetine MOA
* All sorts of serotononergic (differs according to receptor)
* Effective and well tolerated
* Evidence for improvement of difficult to treat cognitive symptoms - concentration and memory etc
27
Vortioxetine side effects
* Nausea - less severe than Venlafaxine
28
How to choose which antidepressant to use?
* What has been used before?
* Was it effective and/or well tolerated?
* Particular symptoms or co-morbidities you may want to address eg weight loss, insomnia (Mirtazapine for both) neuropathic pain (SNRI)
* Patient request - some placebo effect will aid their actual effect
29
What antidepressant to use in new cases with no previous treatment?
* SSRI (Sertaline) unless major weight loss or major sleep difficulty - if this is the case consider Mirtazapine
* If co-morbid neuropathic pain - SNRI
30
What to do if SSRI not working?
* Switch to different SSRI - seems counterintuitive but some genetic variability in receptor sites
* If no effect switch to SNRI, vortioxetine or Mirtazapine
31
When to increase the dose or switch?
* Usually be an effect within first 3 weeks but if you can, wait 4 weeks before making final decision
* For depression - if no benefit, not worth increasing dose - switch. If partial benefit, increase dose.
* For anxiety - consider increasing dose if no initial benefit (esp OCD)
* If significant side effects these may get better in couple of weeks, but if big problem - switch (benefit often comes slower after side effects)
32
What is discontinuation syndrome?
* Not addictive but can be difficult to stop
* Influenced by half life - shorter half life = bigger problem
* Influenced by dose - higher dose = worse
* Very unpleasant but NOT life threatening
33
Discontinuation syndrome symptoms
* Sweating
* Shakes
* Agitiation
* Insomnia
* Headaches
* Irritability
* Nausea + vomitting
* Parasthesia
* Clonus
34
Worst antidepressants for discontinuation syndrome
* Paroxetine and Venlafaxine trickiest to stop
35
Discontinuation syndrome - how to prevent
* Go slow
* Snap tablets in half
* Break capsule - reduce amount of granules per day
* Sometimes worth switching to fluoxetine (very long half life) and then can reduce fluoxetine (can come as liquid and reduce by small doses at a time)
36
What is serotonin syndrome?
* High abrupt increase in serotonin
* Very vague presentation
37
Symptoms of serotonin syndrome
Cognitive:
* Headaches
* Agitation
* Hypomania
* Confusions
* Coma
Autonomic:
* Shivering
* Sweating
* Hyperthermia
* Tachycardia
* Nasuea
* Diarrhoea
Somatic:
* Myoclonus
* Hyper-reflexia
* Tremor
38
Management of serotonin syndrome
* Fluids and monitoring
39
Worst drug for serotonin syndrome
Fluoxetine - long half life
40
PR prolongation for for QTc men vs women
* 450s for men
* 470s for women
* Cardiologists get concerned when going above 500
41
