Which statement about dehydration and drug half-life in older adults is correct?

Which statement about dehydration and drug half-life in older adults is correct?

• A. Dehydration shortens the biological half-life of drugs.
• B. Dehydration has no effect on drug half-life.
• C. Dehydration decreases the half-life of drugs.
• D. Dehydration can increase the half-life of drugs.

Answer: (D)

In pharmacokinetics, a drug’s half-life is shaped by clearance and the volume of distribution. Dehydration in older adults reduces circulating blood volume and renal perfusion, which lowers kidney filtration (and can impair liver clearance as well). When clearance drops, the body removes the drug more slowly, so the half-life lengthens. This is especially important for drugs cleared by the kidney, where accumulated drug can lead to toxicity. So, dehydration can increase how long a drug stays in the body, raising the risk of adverse effects if doses aren’t adjusted.

In pharmacokinetics, a drug’s half-life is shaped by clearance and the volume of distribution. Dehydration in older adults reduces circulating blood volume and renal perfusion, which lowers kidney filtration (and can impair liver clearance as well). When clearance drops, the body removes the drug more slowly, so the half-life lengthens. This is especially important for drugs cleared by the kidney, where accumulated drug can lead to toxicity. So, dehydration can increase how long a drug stays in the body, raising the risk of adverse effects if doses aren’t adjusted.