February 8, 2023

Hey Everyone!

Welcome back to mad medicine in this lecture we’re going to be discussing lithium in buspirone these are gonna be two drugs you definitely need to know for step one and if you guys don’t know we have already covered our antidepressants from the typical all the way to the atypical antidepressants and you can find these videos on our youtube channel youtube.com/weiutv

Where all of our usmle step one videos are located so you can check out our site and some of our forum videos there if you guys don’t know you can also like comment subscribe to our channel and please subscribe it obviously helps us out and with that being said let’s start talking about lithium lithium is the first known medical therapy for bipolar disorder and i

Put this in red because this is definitely something you need to know because it’s high-yield for step one when it comes to bipolar disorder the first-line treatment is going to be lithium okay that is the main thing you need to remember because they will ask you which drug should you use to treat this patient who’s prevent who’s presenting with bipolar mania and

The reason why we use lithium is because it treats them acute manic episodes but it not only treats those manic episodes it also prevents relapsing for patients who have had a history of bipolar disorder and make sure that they don’t go back into those manic episodes it keeps those that occurrence low and so that’s why we use lithium practically when it comes to

Bipolar disorder now obviously this comes at a cost because the thing it has many toxicities and we’re gonna talk about those toxicities in a little bit but because of these toxicities you can guess that in lithium has a very narrow therapeutic index this narrow this very narrow therapeutic index actually contributes to the toxicities because it’s very easy to have

High levels of lithium based off of corrupted drug interactions and the intake level and other you know problems with your body so in order to prevent these toxicities we often monitor the level of lithium in our serum for lithium toxicity this is very important it’s usually moderate now when it comes to the mechanism of action we actually don’t know exactly what

Happens which is good for you guys you don’t need to remember a specific moa for lithium boy you do need to know as that lithium is thought to inhibit phosphor an acetal cascade by inhibiting by inhibiting inositol mono phosphatase that’s what we think it does so when it comes to the basics for lithium just remember that it’s the first time treatment for bipolar

Disorder and it’s thought to work by inhibiting that a certain amount of phosphatase in the phosphor inositol cascade now of course if that was the only thing you need to know that would be great but it’s not you need to understand how lithium kind of functions in our body and in order to understand the toxicities you definitely need to know how lithium is excreted

Now the good thing is it’s almost exclusively excreted by the kidney now we’re specifically in the kidney well it’s going to be absorbed in the proximal proximal convoluted tubule excuse me in the pct and via the sodium channels now if you guys remember back in undergrad you use this one thing called a periodic table and it looks something like this okay and you

Have hydrogen here and right under here you have lithium and then you have sodium and your third in your third row now lithium as you can see it’s in the same column as sodium so it has a lot of the same chemical properties as sodium so that’s why you can think about sodium and lithium as being very closely related right obviously they’re not exactly the same

When it comes to human biologic function but it’s very similar and closely related when it comes to execution now this is going to be a very big contraindication if there is significant renal impairment if someone’s kidneys aren’t functioning properly and if they have some sort of renal disorder that’s happening obviously you can understand that in that case you

May not want to give someone lithium because they’re not gonna be able to excrete lithium in their urine right that is gonna lead to higher dosing of lithium and q toxicity will occur now it’s not just kidney impairments right kidney impairments is just one thing that can happen and another thing that can happen or is gonna be drug to drug interactions and that

Makes a lot of sense because lithium is excreted in the proximal convoluted tubule via the sodium channels in the kidneys well there are a lot of drugs that can interact with lithium especially it say if you have a patient who has bipolar disorder and hypertension and you’re giving those patients some sort of hyper antihypertensive drug like a thiazide or a loop

Diuretic you can lead to increasing levels of lithium so what drugs cause interactions will you need to know the thiazide like hydrochlorothiazide nsaids and ace inhibitors are gonna cause an increase in lithium levels it’s gonna lead to an increase okay that’s very important so you might be presented on step one with a patient who is taking a thiazide or who is

Taking a lana pearl an ace inhibitor so something like that well if that’s the case and those those patients also have lithium and they’re presenting with lithium toxicity what’s the cause it’s going to be drug to drug interactions now another drug that you need to know is the case sparing diuretics like a miller right these can cause a decreased level of lithium

Okay so when it comes to thiazide you’re gonna have increased levels you know with potassium sparing drugs you have decreased levels and with loop diuretics you’re gonna have a varying effect that’s gonna lead to increase or decrease levels but just know you need to watch out for drug to drug interactions when it comes to patients who are taking lithium now that is

Pretty much all the background information you know about lithium we’re not gonna go ahead and talk about the side effects of lithium the there are several side effects especially for step one both in adults and in fetuses that you need to understand and have a good understanding of because you will be tested about lithium in one way or another while or studying for

Step 1 so let’s start off talking about the side effects of lithium we’re gonna solve in my opinion with the most simplest side effect which are tremors right this is gonna be because this is usually gonna happen symmetrically in the upper extremities and this is the most common symptom that occurs and but this ends up resolving over time this is not something that

Lasts long time it’s this isn’t at cute symptoms right so this can be acute tremors now that’s the only acute symptom of lithium or the cute side effect you need to know the rest of these side effects are going to be long term side effects so the first long-term side effect is gonna be hypothyroidism right lithium is a goiter jen and if you guys remember gorgons

Suppress thyroid hormone release that’s what ends up happening they actually prevent the release of thyroid hormone so what you want to do in this case is you want to treat patients who have hypothyroidism with levothyroxine instead of stopping lithium you want to supplement the t3 t4 in order to make sure that their thyroid levels become normalized instead of

Stopping lithium because remember lithium not only decreases the amount of the frequency of those events of those both bipolar manic episodes but it also just you know reduces bipolar mania and it’s used to treat acute bipolar mania as well so you don’t want to stop lithium you actually just want to make sure you can supplement the the thyroid medication just the

Thyroid levels by giving levothyroxine so that’s one of the main long-term side effects so hypothyroidism the other main side effect is gonna be nephrogenic nephrogenic diabetes insipidus right it’s not going to be centered and centric or central diabetes insipidus because this lithium really doesn’t play a main role in your brain when it comes to side effects it

Is gonna play a huge role when it comes to your kidneys and therefore it’s gonna lead to nephrogenic diabetes insipidus now what ends up happening is you’re gonna have chronic tubular interstitial nephropathy which means a patients are gonna present with an inability to concentrate their urine and this the the main clinical presentation is gonna be patients who are

Polydipsia and polyuria they have a lot that really thirsty and they are always peeing now in this case you want to stop lithium if it’s possible all right that’s the main treatment that’s the main thing just keep in mind a question for the usmle step one might be a phrase like what is the main side effect you should be worried about when it comes to patients who

Are taking medications first-line medications for bipolar disorder so first you need to realize the first time medication for bipolar disorder is maybe lithium and then based off of everything that’s on the questions you’re gonna be able to or on the answers you’re gonna be able to deduce it’s gonna be nephrogenic diabetes insipidus so just keep that in mind now

Those are three of the five side effects the last two are also very important the first one is called is the fact you’re gonna have cardiac side effects like suppression of the sa node which leads to bradycardia and syncope and finally and this is very important to us to do with the fetus lithium is one of the main reasons a baby can be born with something called

Epstein’s anomaly epstein’s anomaly is when you have the arterial ventricular displacement of the tricuspid valve so if this is your normal heart right this is your left side your left atria and then you have your left ventricle right here okay so we’re just going to do this so this is all myocardial tissue okay so normally your tricuspid valve is located kind of

Up here right and epstein’s anomaly it actually moves down so it’s gonna be displaced a little bit lower which means your right atria is gonna increase in size that’s what ends up happening and the reason why is a lithium is it try genic it’s not recommended for patients who are pregnant they should not be taking and it completely equilibria across the placenta

Meaning it has effect to cause harm to a fetus when a patient is taking it for that reason it is usually discontinued in pregnant patients in order to prevent any cardiac anomalies when i come or cardiac in general disorders when it comes to the fetus now that is pretty much everything you need to know about lithium i know lithium is a very very dense drug and

There’s a lot of things going on so definitely take your time with this make sure you understand everything that is happening for step 1 and now we’re gonna go ahead and talk to with our last talk about our last drug and that is a drug called boosts pirone now boosts pirrone is a drug that’s very similar to vilasa don’t own and vagyok sateen because boost firown’

Stimulates the 5ht 1a receptors aka the v the serotonin 1a receptors now if you guys remember back to our atypical antipsychotics we talked about two drugs right and those drugs were vil as dome and for tia satine these were you two the last two atypical antipsychotics and both of these also had v h t1 a receptor stimulation activity so they are very similar in

That sense now buspirone on the other hand is not used really for a depression it’s mainly used for generalized anxiety disorder now keep in mind ssris are still gonna be your first time treatment for gid that’s always what you’re gonna go with but if that doesn’t work you can use booster on which is used for generalized anxiety as well the reason why is that this

Drug does not casas dacian addiction or tolerance that’s the first thing and the second thing is that it takes about one to two weeks to take effect a lot faster then ssris ssris usually take four to eight weeks for it to actually have an effect sing with snris but boosts perón usually takes one to two weeks and then it becomes active now it also does not interact

With alcohol like barbiturates or benzos so it’s very safe to take with alcohol especially for patients of general anxiety disorder this is pretty much everything you need to know for booze pirone and with that being said thank you so much for listening to this lecture about lithium and boost road don’t forget to like comment and subscribe to our channel and when

You do really appreciate it if you guys the bail notification so you guys are notified everybody tell me post we also post these on our podcast so you can just search mad medicine wherever you listen to podcast and wolf will pop up thank you so much and continue on to the next topic

Transcribed from video
Lithium and Buspirone (Psychiatry) (Pharmacology) – USMLE Step 1 By MadMedicine