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NBME 20 Answers

nbme20/Block 3/Question#33

A 31-year-old woman receives a prescription for ...

Formation of complexes with mineral ions

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 +6  upvote downvote
submitted by laminin(10),

Tetracyclines have a high affinity to form chelates with polyvalent metallic cations such as Fe+++, Fe++, Al+++, Mg++ and Ca++. Many of these tetracycline-metal complexes are either insoluble or otherwise poorly absorbable from the gastro-intestinal tract. Milk and other dairy products, antacids containing polyvalent cations, as well as various iron salts ingested simultaneously with tetracycline derivatives, might interfere with their absorption by 50 to 90% or even more. source: https://www.ncbi.nlm.nih.gov/pubmed/946598

almondbreeze  FA 2019 pg. 192: Do not take tetracyclines with milk (Ca2+), antacids (eg. Ca2+ or Mg2+), or iron-containing preparations b/c divalent cations inhibit drugs' absorption in the gut +  




 -1  upvote downvote
submitted by hungrybox(433),

Here's my reasoning for why the answer I chose was wrong...

Casein is a milk protein. Because most milk is pasteurized, all proteins will be denatured before consumption, and would not have any effects (Choice B).

This is in contrast to avidin, which is found in RAW eggs and binds vitamin B7 (biotin), preventing carboxylation.

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bullshit question btw 😡