Pharmacology · patient case question
An antibiotic is being considered for this patient. Which age-related change most influences the choice and the dose?
Patient case: Dependent older adult with a full-time caregiver
Patient: Male, 88 years old
Chief Complaint: Brought in by his caregiver for a check-up. He does not report any pain.
Background: Lives at home with an all-day caregiver. Takes eleven regular medications including an antihypertensive, an anxiolytic and a statin. He cannot brush effectively on his own.
Current Findings: Generalised cervical (Class V) carious lesions on the buccal surfaces of most remaining teeth. Marked xerostomia. Heavy plaque. He tires quickly in the chair.
Vital Signs: BP 142/84 mmHg · HR 76 bpm
Show answer and explanation
Correct answer: C. A decline in glomerular filtration rate
- A. Total body water DECREASES with age while the proportion of body fat rises. This raises plasma levels of water-soluble drugs and prolongs the effect of fat-soluble ones.
- B. Serum albumin tends to FALL with age, which raises the free fraction of highly protein-bound drugs — again the opposite direction to what is stated here.
- C. CORRECT. Glomerular filtration falls steadily with age, so renally cleared drugs accumulate. That means longer half-lives, higher plasma concentrations and greater toxicity risk at standard adult doses. Renal function — not chronological age alone — governs dose adjustment.
- D. Gastric acid production tends to DECREASE with age, which can alter absorption of some drugs, but it is not the governing consideration for antibiotic dosing.