Which of the following drugs is most likely to cross the placenta at - ProProfs Discuss
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Which of the following drugs is most likely to cross the placenta at the fastest rate?
The placental crossing of different drugs was studied in laboratory animals. The following data were obtained.



A. Drug A
B. Drug B
C. Drug C
D. Drug D
E. Drug E
Asked by Benjamin, Last updated: Feb 26, 2019

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Block 9 Pharm Drug distribution w exp

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2 Answers

R. Barnes

Always excited to learn and talk about new topics

R. BarnesAnalyst, PhD, Clinton
Analyst, PhD, Clinton

Answered on Feb 26, 2019

The correct answer to this question is A. The membranes separating fetal blood from maternal blood resemble cell membranes. Therefore, drug factors affecting placental transfer include the molecular size of the drug (drugs with mw greater than1500 cross the placenta poorly).

Drug A has a very small molecular weight and is not protein bound. Since it is 100 % ionized, it will be completely water soluble and will easily cross the placenta by aqueous diffusion throughwater channels (aquaporins).

Drug B will cross the placenta slowly since it is highly protein bound. Drug C and E will cross the placenta with difficulty because of their high molecular weight. Drug D will cross the placenta with difficulty because it is mainly ionized.

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John Smith

John Smith

Answered on Sep 09, 2016

Drug a-2) learning objective: outline the main drug factors that can affect the placental transfer of adrug.answer: athe membranes separating fetal blood from maternal blood in the intervillous space resemblecell membranes elsewhere in their general permeability behavior. therefore drug factorsaffecting placental transfer include the molecular size of the drug (drugs with mw greater than1500 cross the placenta poorly) as well as its physicochemical properties (lipophilic drugsdiffuse readily, highly ionized drugs with mw higher than 200 cross the placenta slowly) and itsdegree of protein binding (drug highly protein bound cross the placenta slowly).drug a has a very small molecular weight and is not protein bound. since it is 100 % ionized itwill be completely water soluble and will cross easily the placenta by aqueous diffusion throughwater channels (aquaporins).b) this drug will cross the placenta slowly since it is highly protein bound.c, e) these drugs will cross the placenta with difficulty because of their high molecular weight.d) this drug will cross the placenta with difficulty because it is mainly ionized, i.e. water soluble,and too big to permeate the membranes by aqueous diffusion.
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