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NBME 22 Answers

nbme22/Block 2/Question#45 (42.9 difficulty score)
An 86-year-old man who lives in a skilled ...
Dextromethorphan🔍
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 +10  upvote downvote
submitted by rockediny(10),
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texorD si eth oecctrr naewsr .rhee rmoF eth eicshco nvgie, dterox is hte etasl ikelly to scuea itnoscitnpao cnsei tsi mnai cmmhensai fo ioantc si AMDN antngosiam /wmseo ipdoio taiycvti -- it nac cesua iaioontpctsn but the rthoe iehccso rea CHUM OEMR kleiyl t.o As fro penheddnayrmhii = ti si ont ipporetarpa ofr elrylde stnepati nda it tns’i na uiaie.svsttn

forerofore  diphenhydramine and other Gen 1 antihistamines are good choices for chronic cough in allergy and patients with posterior draining and post viral chronic cough (careful with the elderly). That being said, apparently it also causes constipation, so dextro is still the correct answer. +2  
passplease  Could it also be that you would not prescribe diphenyhyrdramine because they are part of the beers criteria and should be avoided in the elderly? +1  



 +2  upvote downvote
submitted by noselex(4),
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roexDt vs nC:eeodi oBht aer ivtsusait,ens ubt torxde is orme fo MNDA stoinga ahtt osal ash oiipdo tsoaing .cyiittva oxrtDe is eonft easubd ot tge a iilrasm uot fo body iglfene edu to sti MDAN oaigstn .eecftf idCeone on hte othre oehrt is a l-fnuol iipood ginto.as Its’ losa duse sa e,ladii-hnrtraa os ctsapniontio is evyr oocmmn edvrsea ec.ffet

miopTtoiur is rwong besaeuc i’ts ont na asisivut.tne ls,oA ti’s na gchaniirtelnico hwcih si ()1 idacdniactotern in deyelrl lnsues aeryll ai,dcientd 2() a mdul-dtwoclenee lhiaocngcrnitie cetfef is ni.tnosapctoi

pparalpha  According to Sketchy and Amboss: dextromethorphan is a weak opioid receptor AGONIST and NMDA receptor ANTAGONIST (it's not an agonist). +2  



 +2  upvote downvote
submitted by joanmadd(4),

in NBME 20 there is a question where a pt starts taking an antitussive and has constipation. The offending drug was dextro.... confusing, man...




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How is a tisenhtyc oiipdo mdr)h(oteoaprtehxn ahtt ouy acn dnfi hiwt a 2 dscneo loggoe chsare sa iguacns cinottspnoia hte crrecto n?aeswr sI it stuj ecbause iuorpitomt dutw’lno ttaer eht ?hguoc

moneysacs  Tiotropium would cause constipation bc it’s an anticholinergic. Don’t have any insight into why dextromethorphan is the right answer though, other than process of elimination and diphenhydramine wouldn’t treat his symptoms. +1  
upstairs_bumblebee  I thought it was dextromethorphan because it would bind NMDA receptors and have weaker opioid effect = less constipation? Idk though :/ +  
dr_salface  I agree. I mainly went by way of elimination but even DXM made me think of opiod-induced constipation. Though, all the other answer choices had obvious anticholinergic effects. At least, that was my reasoning for picking dxm. +  



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reP ifstr d.ai hhperanoDxtremto = evtn“iAsstui gtaeisnaon(z MNAD uleamgtat r).psecoter ntieSytch enicode a.nlaog saH imld poiiod fteecf wneh sued in ”xee.css

I seusg eht yke si htat eth oodpii fetfce is dlm.i Sesem ikle r’hteye kisnga hihcw duolw raett eht smptsomy and urceed the dsie efstefc, nto ersisealncy etg rdi fo the sedi ctfsfee elepolct.my gAere taht ti si a cllgninegha oen for eSpt 1.




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NEMB 02 has a nesqutoi wiht a guy akgnit eovr the oretnuc hgouc eminatocid dan won eh ahs iosnitotacnp. tnaW ot ssgue het re?answ It swa xeodrt! gt-&; 2srmwe0//p.naembhmse84/axm/onts/c:5nbte

oS Im’ pttyre resu teh MNEB 22 iosnqetu si tsju ishtrgat up .gnorw

rockediny  No, not so. Dextro *is* the correct answer here. From the choices given, dextro is the least likely to cause constipation since its main mechanism of action is NMDA antagonism w/ *some* opioid activity -- it can cause constipation but the other choices are MUCH MORE likely to. As for diphenhydramine = it is not appropriate for elderly patients and it isn’t an antitussive. +  
surely_not_a_robot_  Agreed with @rockediny. Dextro would be the best to prescribe because it has the least amount of constipation out of the drugs that you could prescribe + Anti-cholinergics in the elderly have much more morbidity and risk of mortality. +  
keycompany  The only way to wrap your head around this is to conclude that Dextro is the "least wrong". I thought a lot about this, and I can't think of any drugs that can suppress cough without also causing constipation, so it makes sense that Dextro is the answer because it is the "least likely" to cause significant constipation. This is probably just a clinical correlate that will be learned during rotations/years in practice. +