Geriatric Medicine

Answer 4 Decreased muscle mass (sarcopenia) is the basis for normal or low creatinine levels in older patients, despite a decrease in renal function. Creatinine is a derivative of muscle; sarcopenia (low muscle mass) is the basis for low serum creatinine levels in elderly patients, despite a decrease in renal function. A creatinine level of 1.5 mg/dL denotes a creatinine clearance of less than 50 mL/min in an older woman, which is abnormally low. Aging is generally associated with a decrease in the glomerular filtration rate (creatinine clearance) at the rate of 1 mL/min per year of life, although this decrease is not invariable. Tubular function also decreases with aging. Gentamicin, an aminoglycoside, should be administered in lower dosages in geriatric patients than in younger patients, because a lower creatinine clearance and a smaller amount of water in the body lead to a higher drug concentration and the risk of toxicity. SUGGESTED READINGS 1. Dharmarajan TS, Tota R. Appropriate prescribing of medications in older adults. Fam Pract Recert 2000;22:29-38. 2. Leipzig RM. Pharmacology and appropriate prescribing. In: Cobbs EL, Duthie EH, Murphy JB, editors. Geriatrics review syllabus, 4th ed. Dubuque (IA): Kendall/Hunt Publishing Co; 1999:30-5. 3. Schwartz JB. Clinical pharmacology. In: Hazzard WR, Blass JP, Ettinger WH, et al, editors. Principles of geriatric medicine and gerontology. 4th ed. New York: McGraw-Hill, Health Professions Division; 1999:303-31. Click here to return to the questions

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