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NBME 21 Answers

nbme21/Block 2/Question#39

A 64-year-old man with bronchospastic pulmonary ...

Enhanced action of the agonist at β-adrenergic receptors

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 +3  upvote downvote
submitted by wasabilateral(15),

This is what I thought but not sure if it’s correct. There is a UWorld q where it describes co-administration of cortisol and epinephrine. Cortisol significantly enhances the effect of epi because cortisol has a permissive effect on maintaining the adrenergic receptors.

194orbust  per UWorld, "cortisol exerts a permissive effect on many hormones to help improve the response to a variety of stressors. For example, cortisol increases vascular and bronchial smooth muscle reactivity to catecholamines". FA also uses the effect of cortisol on catecholamine responsiveness as the lone example for a permissive drug interaction (FA2018 pg 229). The difference here is that we're talking about exogenous glucocorticoid and adrenergic agonist. I guess it was expected for us to assume that the mechanism is analogous for the analogous drugs +1  
maxillarythirdmolar  I'm sure it's related to the activating effect of Cortisol on phenylethanolamine-N-methyltransferase, converting NE to Epi. Sounds like a synergistic thing to me. (FA.83) +1  




 +2  upvote downvote
submitted by 5thgencephalosporin(2),

“The combination of a long-acting beta 2 agonist (LABA) and an inhaled corticosteroid is more efficacious in asthma and [COPD] than [...] either alone. Corticosteroids may regulate beta 2 receptor function by increasing expression of the receptor, restoring G-protein/beta 2 receptor coupling, and inhibiting beta 2 receptor downregulation.”

https://www.ncbi.nlm.nih.gov/pubmed/16113435

sahusema  In short, cortisol upregulates adrenergic receptors and makes them more sensitive +  




 +0  upvote downvote
submitted by sam1(0),

This seems to be a relevant paper: https://www.ncbi.nlm.nih.gov/pubmed/11897997

"These data indicate that glucocorticoids only transiently enhance beta(2)AR gene transcription and fail to increase steady-state levels of beta(2)AR protein in human airway epithelial cells. Nonetheless, glucocorticoid-induced effects on the beta(2)AR-AC system of human airway epithelial cells contribute to the beneficial effects of corticosteroids in asthma by enhancing the functional response to beta(2)-agonists."





 +0  upvote downvote
submitted by maxillarythirdmolar(1),

I'm sure it's related to the activating effect of Cortisol on phenylethanolamine-N-methyltransferase, converting NE to Epi. Sounds like a synergistic thing to me. (FA.83)