Which statement best describes the relationship between absorption and distribution?

Which statement best describes the relationship between absorption and distribution?

• A. Absorption is not required for distribution
• B. Absorption is required for distribution
• C. Absorption occurs after distribution
• D. Absorption guarantees brain distribution

Answer: (B)

The main idea is that a drug must reach the bloodstream through absorption before it can be distributed to body tissues. Absorption brings the drug from the site of administration into systemic circulation, and distribution is the process of moving that drug from blood to tissues. Without entering the blood, there’s nothing to carry to organs, so distribution can’t occur for routes that require absorption. It’s worth noting that giving a drug IV bypasses the absorption step, so distribution can begin immediately from the bloodstream. But in general, absorption provides the pool of drug that enables distribution. Also, absorption does not guarantee that the drug will reach the brain—getting into the brain depends on factors like crossing the blood–brain barrier, which depends on the drug’s properties, not just absorption.

The main idea is that a drug must reach the bloodstream through absorption before it can be distributed to body tissues. Absorption brings the drug from the site of administration into systemic circulation, and distribution is the process of moving that drug from blood to tissues. Without entering the blood, there’s nothing to carry to organs, so distribution can’t occur for routes that require absorption.

It’s worth noting that giving a drug IV bypasses the absorption step, so distribution can begin immediately from the bloodstream. But in general, absorption provides the pool of drug that enables distribution. Also, absorption does not guarantee that the drug will reach the brain—getting into the brain depends on factors like crossing the blood–brain barrier, which depends on the drug’s properties, not just absorption.