Distinguished future physicians welcome to Stomp on Step 1 the only free videos series
that helps you study more efficiently by focusing on the highest yield material.
I’m Brian McDaniel and I will be your guide on this journey through Antidepressants.
This is the 8th video in my playlist covering all of psychiatry for the Step 1 medical board
exam.
We are going to review mechanisms, indications and side effects for the various antidepressant
classes including tricyclic antidepressants, SSRIs, SNRI and atypicals.
I originally planned on having antipsychotics, anxiolytics and mood stabilizers in this video
also, but it was getting way too long so I split those meds off into their own video
which will be next in the series.
It is tough to break the high yield rating down by subclass like I usually do, so this
time I will just give you the high yield rating for all of antidepressants at once.
Overall antidepressants get a High Yield Rating of 9 for the Step 1 medical board exam.
This means based on a number of factors (including the frequency of appearance on retired step
1 questions) you are almost definitely going to see at least 1 question on your exam about
antidepressants.
By far the most important aspect is the side effects for these medications.
Most questions are going to be about SSRIs and TCAs so focus your attention there.
MAOIs are very old, rarely used anymore and unlikely to show up on the exam, but you may
see them on older practice tests.
I’m going to focus on pharmacologic treatment for depression because that is what the test
questions are on, but remember there are alternatives to meds.
Cognitive Behavioral Therapy and counseling can have similar efficacy to medications.
Using meds and CBT together is the best options.
Also Electroconvulsive Therapy (or ECT) can has even better results and faster onset than
medications.
But the stigma for ECT and common side effect of amnesia means that it is usually only used
in severe depression with patients who can’t tolerate medications.
I will start with some general principles that apply to all of the antidepressants and
then we will talk more specifically about each class.
One hypothesis for the pathophysiology of depression is that it is due to low levels
of monoamine neurotransmitters (mainly serotonin, norepinephrine and dopamine).
That is why antidepressants aim to increase the levels of these neurotransmitters in the
synaptic cleft.
They do this by slowing the reuptake of the neurotransmitters so that they stay in the
cleft longer and interact with post synaptic receptors more often.
The first drugs in this group were non-specific and increased all of the monoamines, which
lead to lots of side effects and safety issues related to toxicity.
Newer antidepressants are more selective and mostly only effect the reuptake of 1 or 2
monoamines.
Unfortunately, antidepressants take at least a month to start working.
Good patient education about the delayed onset of effect and close monitoring of the patient
during this initial period is extremely important.
Patients can become hopeless if they expect the drug to start working right away.
This may be one reason why antidepressants are associated with suicide, especially in
patients 25 years old and younger.
Another proposed mechanism is that a depressed person may have the energy to carry out their
suicide once the medications start to work.
There is now a black box warning for suicide on antidepressants.
Some psychiatrists argue that they don’t actually see this association with suicide
in clinical practice, and that the thing that really increases the risk for suicide is not
treating a depressed person with the proper medications.
However, it is still standard practice to have a close follow up with patients you are
starting on antidepressants.
Usually this will involve a follow up visit about 2 weeks after the medication is started.
At this visit the drug will not have started working yet so you can’t evaluate efficacy,
but you can monitor for side effects like suicidality.
Another serious side effect you have to be on the lookout for soon after initiating treatment
is mania.
If a bipolar individual is incorrectly diagnosed as having depression, an antidepressant may
induce a manic episode.
Another very serious side effect that has to be considered for antidepressants is Serotonin
Syndrome.
This usually occurs when you combined multiple antidepressants at the same time or combine
an antidepressant with another medication that increases serotonin such as dextromethorphan
or an opioid.
It presents with tremor, diaphoresis, tachycardia, flushing and hypertension.
If not corrected it can progress to delirium, AMS and death.
Treatment includes medication cessation and the use of Cyproheptadine (a serotonin antagonist).
In order to prevent this from happening you should have about a month “Wash Out” period
when you are switching between antidepressants.
So you taper the 1st medication down and then stop it, give the patient at least a month
with no antidepressant and then start adding the new medication slowly.
Most side effects begin immediately after starting the medication, but diminish over
the course of a month.
A principle that applies to all of the antidepressants is “start low and go slow.”
This means that you start with a lower dose and slowly increase it in order to decrease
side effects and increase patient compliance.
The dose you start the patient on may not even be at a therapeutic level, but every
month or so you can increase the dose a bit.
Everyone reacts differently to antidepressants.
Some will inevitably be partial responders or non-responders to certain drugs that you
prescribe.
Oddly, patients may react differently even to drugs within the same class.
For example, one SSRI may work great for a patient while another SSRI does nothing for
them.
This is why treating depression is sometimes a trial and error process.
Since there is a delayed onset of effect you usually work your way up to the max dose and
wait for about 6 weeks before switching to another medication.
About half of people who have their first depressive episode will eventually relapse
and have another episode of depression.
Therefore, treatment is usually continued for at least a year after their first episode
of depression.
After 2-3 episodes of depression the odds of having another depressive episode are so
high that most docs would treat with antidepressants for life.
Most antidepressants can have a withdrawal effect if they are discontinued abruptly.
It can presents with a wide variety of symptoms including insomnia, flu like symptoms and
changes in mood.
Antidepressants with short half-lives like Paroxetine more commonly have withdrawal effects.
To prevent withdrawal most antidepressants should be tapered before discontinuation.
So we will start with tricyclic antidepressants (or TCAs).
The most high yield meds for this class are Amitriptyline, Nortriptyline, Imipramine,
Clomipramine & Doxepin.
* It is easy to remember because almost all
of the drugs in this class (even those I didn’t specifically list) end in iptyline or ipramine.
Tricyclic Antidepressants (TCAs) block reuptake of norepinephrine and to a lesser extent serotonin.
They are more selective than the very old MAOIs, but not as selective as SSRIs and SNRIs.
This is why they have largely been replaced by SSRIs/SNRIs as first line depression treatments.
They are still used to treat depression resistant to other antidepressants as well as off label
use for a number of other conditions including fibromyalgia, chronic pain/neuropathic pain,
and enuresis (or loss of control of urination such as bedwetting).
If a patient has depression and something like a chronic pain syndrome than it should
be your first choice.
Side effects limit the use of TCA.
The most common side effects fall under the category of anticholinergic.
Depending on the specific side effect you may be able to more specifically describe
these at anti-muscainic, antihistamine or anti-adrenergic effects.
They include dry mouth, blurry vision, urinary retention, constipation, sedation, orthostatic
hypotension, and cognitive impairment.
These symptoms are not nearly as common in newer antidepressants.
* Like SSRIs insomnia, weight gain and sexual
dysfunction are also common side effects.
There are also rare but very serious cardiac adverse reactions.
TCAs can cause QT interval prolongation, which is why they are contraindicated in those with
underlying conduction abnormalities and recent MI.
An EKG should be done before starting a patient on TCAs.
TCAs are also fatal in overdose due to arrhythmias.
This is very risky considering that antidepressants are given to a group of individuals who may
be suicidal.
TCAs are correlated with seizures and coma while also interacting with many different
drugs via their metabolism via cytochrome P450.
Selective-Serotonin Reuptake Inhibitors increase serotonin in the synaptic cleft by decreasing
their reuptake.
They are “selective” because they have less effect on the reuptake of other monoamines
like norepinephrine and dopamine.
They are first line treatment options for depression, OCD, social phobia, PTSD, Generalized
Anxiety, Eating Disorders and other psychiatric conditions.
They are used for so many different things that if you are stuck on a psych med question
and don’t know the answer just selecting the SSRI is probably the safest bet.
Here is the list of the most commonly tested SSRIs.
Paroxetine, Fluoxetine, Sertraline, Citalopram & Escitalopram.
I have included the brand names for each, but remember only generic names will be tested
on the exam.
Each of these has slightly different indications and efficacy, but in general you can get questions
right by just knowing the general characteristics of the entire group.
They have become the first line medication for depression as they have a better safety
profile and fewer side effects than TCAs.
Unlikely TCAs, SSRIs are usually not fatal in overdose.
That is obviously a big advantage when you are treating depressed patients that may be
suicidal.
SSRIs can also have GI problems (Nausea, diarrhea etc.), headache and insomnia as side effects.
These adverse reactions will usually diminish overtime, but if insomnia persists Trazadone
is sometimes added to an SSRI to lessen the insomnia side effect.
The most common side effect is sexual dysfunction which can include anorgasmia, diminished libido
and erectile dysfunction.
Thankfully this side effect can largely be eliminated by combining an SSRI with Bupropion.
The sexual side effects can also be a plus for some patients as SSRIs are sometimes abused
or used off label to treat premature ejaculation.
SSRIs are also associated with bleeding as they can interact with anticoagulants like
Warfarin.
Serotonin-Norepinepherine Reuptake Inhibitors have a similar mechanism to SSRIs but they
block the reuptake of serotonin and norepinephrine.
Other than that SNRIs have very similar indications, efficacy and side effects as SSRIs so I will
not spend much time specifically on SNRIs.
The most commonly used SNRIs are Duloxetine, Venlafaxine & Desvenlafaxine.
That leaves us with the atypical antidepressants.
Their efficacy, side effects and indications are similar to the drugs we have already discussed,
but there are a couple unique features with each that we need to point out.
They work by slightly different mechanisms than the other medications, but that is low
yield so I’m not going to cover that.
The highest yield medications in this group are Bupropion, Trazadone and Mirtazapine.
* Bupropion (or Wellbutrin) does not have sexual
side effects and may actually increase sexual function.
This is why Bupropion is often added to SSRIs, because it counteracts the sexual dysfunction
of SSRIs.
Another important thing to know is that Bupropion can be used off label for smoking cessation.
So if you have a patient who is depressed and wants to quit smoking this is the clear
choice.
A downside to this drug is that it lowers the seizure threshold, especially in those
that are bulimic.
So this medication is contraindicated in people with a history of eating disorders and epilepsy.
* Trazadone is almost never used purely as an
antidepressant anymore, because the side effect of sedation is so strong.
However, Trazadone is commonly used off label as a sleep aid or in conjunction with an SSRI
if they are having insomnia.
The rare but dangerous side effect of this drug to remember is Priapism.
This is a prolonged erection that can lead to impotence if not treated.
Some people remember this side effect by the mnemonic “Traza-BONE”.
* The only high yield thing to remember for
Mirtazapine (or Remeron) is that it commonly has weight gain.
This may actually be a positive thing if you are treating depression in somebody (like
a frail elderly patient) that needs to gain weight.
That brings us to the end of this video.
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* Our next video and the last video in the Psychiatry
section is going to cover Antipsychotics, Mood stabilizers & Anxiolytics.
To be taken directly to that video you can click on this black box here if you are watching
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Thank you so much for watching and good luck with the rest of your studying.