Which of the following is true regarding extent of absorption of drugs?

Which of the following is true regarding extent of absorption of drugs?
A . After oral ingestion of drugs, the absorption of drug may be incomplete
B . Drugs which are too lipophilic cannot cross the lipid cell membrane
C . Drugs which are too hydrophilic are not soluble enough to cross the water layer adjacent to the cell
D . P-glycoprotein is an efflux transporter which is present in the enterocytes and it enhances the absorption of drug
E . Grape juice activates P-glycoprotein leading to substantial inhibition of absorption of drugs

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Answer: A

Explanation:

It is not necessary that all the drugs get completely absorbed after oral administration. Most of them are incompletely absorbed. The extent of absorption varies from 5 to less than 100 % with oral ingestion of drugs. Drugs which are too hydrophilic like atenolol are incompletely absorbed because the drug cannot cross the lipid membrane due to high hydrophilic nature of the drug. Similarly, drugs which are too lipophilic like acyclovir are not soluble enough to cross the water layer adjacent to the cell. P-glycoprotein is an efflux transporter which is present in the enterocytes and it inhibits absorption of drug. It is also known as export transporter or reverse transporter. It has many drugs as its substrate. Grape juice in fact inhibits P-glycoprotein in the intestine thereby decreasing the efflux of drug from the cells by P­glycoprotein. Thus ingestion of grape juice may lead to significantly increased absorption of the drug.