A calculation used to estimate creatinine clearance based on age, weight, serum creatinine, and gender. Estimated creatinine clearance may be used to adjust dosages of renally excreted drugs. This formula is commonly used to adjust dosages for adult patients because their serum creatinine level may be a poor indicator of renal function. Because of decreased muscle mass in elderly patients, the serum creatinine level is a poor indicator of renal function; therefore this formula is used to adjust dosages. For men the formula is (140 – age) (weight in kg)/ 72 X serum creatinine. For women, this result is multiplied by the factor 0.85.