Pharmacology Flashcards
What are the common side effects of adrenergic/noradrenergic receptors?
Sweating Tremor Headaches Nausea Dizziness
Fight/flight
What are the common side effects of muscarinic receptors?
Dry mouth, difficulty swallowing, thirst
Difficulty urinating, urinary retention
Hot and flushed skin
Dry skin
What are the common side effects of histamine?
Dry mouth
Drowsiness
Dizziness
Nausea and vomiting
What are anti-depressants?
Most work on serotonin activity, aiming to increase post synaptic response.
Most have their effect in 2-3wks
Commonly use SSRIs.
Also can use SNRIs, Mirtazapine, Tricyclics, MAOIs.
How do SSRIs work?
Bind to reuptake receptors.
Increase serotonin activity by reducing the presynaptic reuptake of serotonin after release.
So more serotonin in the synapse.
Leading to down regulation of post-synaptic receptors 2-3wks later
What are the side effects of SSRIs?
Sense of restlessness, agitation on initiation (therefore use benzodiazepines)
Nausea
GI disturbance
Headache
Last longer and are more important for people-
Weight changes- most lead to weight loss.
Sexual dysfunction- difficulty experiencing arousal and orgasm.
Less common- bleeding (some serotonin receptors in GI tract platelets) and suicidal ideation (age related)
What is suicide ideation?
Anti-depressants usually increase energy levels before decreasing the suicidal thoughts/suicidality.
Therefore in the initial steps of taking the anti-depressants there is a high risk of suicide. So clinicians should follow up pts after 2wks of prescribing.
More pronounced in men and younger generation.
What are the doses of SSRIs?
Sertraline 50-200mg. Therapeutic dose starts at 100mg. Safest in cardiac disease.
Citalopram- 20-40mg. Ecitalopram 10-20mg. Be weary of QTc prolongation therefore avoid if other drugs have the potential for that.
Fluoxetine 20-60mg. Be weary of serotonin syndrome when switching since long half life.
Paroxetine 20-60mg. Be weary of discontinuation syndrome since short half life.
What are SNRIs?
Act as SSRIs, but bind to noradrenaline reuptake receptors as well.
Evidence base for neuropathic pain
Two types-
Duloxetine (UK liscensed for neuropathic pain) 60-120mg
Venlafaxine 75-375mg. Caution at higher doses in heart disease, can cause HTN at higher doses so ensure monitoring if 225mg+
What are the side effects for SNRIs?
Same as SSRIs but also
What is mirtazapine?
5H2/3 antagonist
Strong histaminic activity- causing sedation
Major side effects weight gain and sedation.
Side-effects occur at low and high doses, therefore not dose dependent.
These ‘side effects’ can be used for therapeutic advantage i.e. pt lost weight and struggle to sleep. Most pt take this early evening/night.
What are tricyclics?
Used less due to tolerance
All have potential to give muscarinic and histaminic side effects.
More fatal in overdose- QTc prolongation and arrhythmias
Used at low dose for neuropathic pain
Newer- lofepramine and nortriptylines tolerated better than older amitryptilines.
What are MAOIs?
Type A work on serotonin more.
Type B work on dopamine more.
More effective for atypical depression- pt sleeps more and eats more.
Irreversible- more dangerous phenelzine, isocarboxazid
Reversible- less dangerous moclobamide trabycypromine.
Risk of tyramine reaction. Too much tyramine leads to more adrenaline and hypertensive crisis. Therefore need to avoid cheese, wine, pickled meats and tyramine products.
Need to be careful when changing to another antidepressant, may require a washout period of 6wks.
Vortioxetine
Newer antidepressant
All sorts of serotonergic activity, sometimes will agonise, sometimes antagonise.
Well tolerated, better than other antidepressants.
Most common side effect is nausea.
Improves difficult to treat cognitive symptoms. Post depression, some people find cognitively they’re still not well I.e. difficulty concentrating, poor memory etc.
Which antidepressant should we use?
Which have already been used for the pt?
Was this effective before? Was it tolerated before?
Are there any particular co-morbidities we wish to address? I.e. weight loss, insomnia, neuropathic pain.
What does the pt want? Sometimes there is a placebo affect if the pt believes a certain medication will work.
What to use
If new case, with no previous treatment- start with SSRIs.
If there is major weight loss or major sleep difficulty then use mirtazipine.
If there is comorbid neuropathic pain then consider SNRIs.
In most cases start with SSRI, if no effect then change SSRI, if no effect then change SNRI venlaflaxine or mirtazapine.
Starting SSRI, usually sertraline.
If the Pt wants a certain drug and there are no contraindications then start it.