January 27, 2023

I cover Cetirizine (Zyrtec) pharmacology, adverse effects, and drug interactions.

Hey all welcome back to the real life pharmacology podcast i’m your host pharmacistera christensen uh thank you for listening today go check out reallifepharmacology.com uh snag a free 31 page pdf on the top 200 drugs a great little study guide if you’re going through board exams pharmacology exams final exams things like that so definitely don’t hesitate to snag

That for free simply an email we’ll get you access to that and then of course we’ll get you updates on when we’ve got new podcasts out which are usually on a weekly basis as well as any other new content as well so again reallifepharmacology.com go check that out all right so let’s talk about the drug of the day today cetirizine brand name of this medication is

Zyrtec it is classified as an antihistamine so i have covered some antihistamines in the past particularly more so some of the first generation antihistamines such as hydroxyzine diphenhydramine now satirizing differs from those and that it is classified as a second generation antihistamine and the biggest thing with second generation antihistamines and i’ll get

Into it when i talk about adverse effects a little bit is they have generally less anticholinergic adverse effects so that’s definitely a good thing because there’s plenty of issues with that if you’ve listened to the uh you know benadryl and the hydroxyzine uh podcasts in the in the past so uh being an antihistamine um allergies is probably the primary reason

That i’m gonna see a patient on this for an extended period of time uh occasionally you see it used for itching sometimes some acute allergic reactions in in rare situations more often i would say i see diphenhydramine used for a more serious allergic reaction to something but in general for seasonal allergies and things like that you’re probably going to see

More second generation antihistamines like satirizing and loratadine which i’ll probably cover in a future episode so mechanistically understanding that their their antihistamines uh they essentially reduce activity binding of histamine at the h1 receptor now remember that differs from h2 receptors so again h stands for histamine so histamine one receptors we’re

More focused on on targeting the respiratory tract obviously if we’re managing seasonal allergies now h2 receptors are more abundantly found within the gi tract and those agents that are are used to target h2 receptors are h2 blockers so things like famotidine for example so again very important you know i’ve seen that come on come across in pharmacology exams and

Things like that understanding the difference between the histamine one and histamine two receptors uh dosing i did want to mention briefly in my practice i see some issues with this occasionally typically for most adult patients they’re going to be taking 10 milligrams once a day in more severe cases i have seen dose escalation up above 10 milligrams most often

If somebody does go higher it’s it’s 10 milligrams twice a day typically you know i i get a little bit more concerned about the potential for anticholinergic and sedative type adverse effects as we escalate that dose but there have been a few occasions where i have seen that higher dose utilized uh per the manufacture recommendations a maximum of 5 milligrams is

Actually recommended in patients 77 years of age and older that’s kind of abnormal cut off there but it is something i have addressed definitely in in older patients particularly let’s say they’re using it for seasonal allergies if it’s really well controlled and they’re on 10 milligrams and they’re an 85 year old for example it’s like okay you know can we give

It a shot and try down to five milligrams and see if it still works for you i think that’s a reasonable thing to do in a lot of patients there if i’m recommending starting it or recommending it to a patient that’s over you know 77 or i guess you know around 80 or higher um five milligrams is probably where i’m going to recommend that they start uh if they’re um

Taking something for for seasonal allergies there uh dosage forms we’ve got a lot of options you will see cetirizine used in pediatric patients definitely so you know having liquid formulation tablets chewable tablets having those multiple dosage forms can certainly be advantageous adverse effects i kind of alluded to a couple think about anticholinergic effects

But with that said the likelihood that that you run into them is pretty low when we’re using kind of our standard dosing most often what i have seen with cetirizine is patients get a little bit sleepy and so you know i’ve i’ve definitely recommended maybe taking it at night especially if patients are experiencing sedation so that’s something to to definitely think

About um of the uh second generation antihistamines uh effexophenidine and loratadine are a couple other examples ceterizine probably is going to be the most sedating of the multiple different second generation antihistamines now keep in mind it is a dose-dependent effect so if you’re using a super high dose of another one compared to a low dose of cetirizine

That might not be true but in general ceteriazine may be a little bit more sedating than some of the others and then of course you know as you escalate dose keeping in mind some of those anticholinergic effects uh dry eyes dry mouth those are probably the ones that i’ve i’ve seen a little bit with cetirizine if i’m if i have encountered anticholinergic effects

But theoretically you know urinary retention constipation um you know confusion cns changes all those can happen with cetirizine but again not incredibly likely that you’re you’re going to run into that uh monitoring parameters so we don’t have any labs monitor that’s nice um so really what you’re gonna do is is monitor symptoms um probably monitor for adverse

Effects like sedation and dry mouth and things like that but having the the no labs is certainly a nice thing all right so let’s take a quick break from our sponsor and we’ll finish up with drug interactions if you’re in the market for pharmacist board certification study material like naplex bcps bcgp ambulatory care mtm psychiatric certification definitely go

Check out our study materials for those individual exams at meded101.com store we’ve got a growing list of resources i’ve been putting content together for well over six six years now um and and i think we’ve we’ve gotten some great feedback and and we’ve really done our best to try to make the the package the most relevant possible and obviously help you prepare

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That so lots of case studies case scenarios and things that i’ve come across in my real life in various books there uh depending upon what you’re looking for so definitely go check out all those links meta101.com store all right so wrapping up with drug interactions fortunately cetirizine it’s over-the-counter agent unfortunately we don’t have a ton of uh drug

Interactions as far as the liver sip enzymes go so that’s a nice thing that we don’t have to worry about the biggest concerns that i run into so if you’ve got a patient that’s presenting with sedation or they’re overly sedated certainly we got to think about some of these agents adding up and contributing to sedation so your opioids alcohol z drugs you know maybe

Older anticholinergics things like that with sedative properties could have additive potential the other additive adverse effect is anticholinergic burden again they aren’t strongly anticholinergic but if you’ve got a patient on you know cogentine oxybutenin uh tricyclic antidepressant um you know maybe even inhaled anticholinergics you might get an exacerbation

Or an additive type effect of you know dry mouth and dry eyes and and some of those things again depending upon the agent depending upon the dose and and kind of that cumulative effect so definitely some things to to look out for there as far as drug interactions go but it satirizing avoiding the sip enzymes is definitely a nice thing all right so that’s going to

Wrap it up for today if you enjoyed the show found it helpful leave a rating review on itunes or wherever you’re listening uh go support the sponsor med101.com store obviously it helps fund the podcast here and keep it free and educational for all to enjoy and of course share us with friends colleagues students that may be working with you help them expand their

Knowledge base and obviously hopefully the goal is to improve medication safety for all i’m going to wrap it up for today if you want to reach out to me comments questions anything med education 101 gmail.com or linkedin is probably the social platform that i’m most active on eric christensen uh pharmd bcps bcgp thanks so much for listening take care hope you have a great rest your day

Transcribed from video
Cetirizine Zyrtec Pharmacology By Eric Christianson