That for the female patient is even lower.
Creatine is eliminated from the body via glomerular filtration and shows no protein binding.
Since creatinine is produced by muscle metabolism, we use the IBW in calculating Cl creat instead of total body weight. If total body weight were used, the clearance would be overestimated. Since we are using Cl creat to estimate GFR, we would overestimate as well. Aminoglycosides are excreted unchanged by renal glomerular filtration. Since the GFR for this patient is lower than normal, we know that the drug is not being eliminated from the body at a usual rate.