The estimated Creatinine clearance rate for a 120lb patient is i40ml/min. what maintenance dose should be administered if the normal maintenance dose is 2mg/lb of the body weight

The estimated Creatinine clearance rate for a 120lb patient is i40ml/min. what maintenance dose should be administered if the normal maintenance dose is 2mg/lb of the body weight?
a- 60mg
b- 100mg***
c- 120mg
d- 160mg
e- 240mg.
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Creatinine - in the internationalized spelling creatinine - is a metabolite. It forms as a strongly basic amide (lactam) from the acid creatine in aqueous solution and irreversible in the muscle tissue. In the body it is a urinary metabolite, so it must be excreted through the kidneys and urine.

Creatinine as metabolic parameter:
Creatinine is an important kidney retention parameter in laboratory medicine. It is excreted in the urine at a relatively constant rate of 1.0 to 1.5 g per 24 h, mostly glomerular, in some cases also active tubular at high plasma levels. However, the rate of excretion is an individual constant, which depends in particular on the muscle mass and age and thus is more suitable medically for the follow-up. Typical values ​​for the excretion rate are 21 to 27 mg / kg / 24 h for ages between 20 and 30 years, 6 to 13 mg / kg / 24 h for those over 90 years of age, in children approximate formula 15.4 + 0.46 × age (mg / kg / 24h).
Many urinary parameters are related to the amount of creatinine excreted. This creatinine reference is not suitable for all substances.
The blood plasma level is around 0.7 mg / 100 ml (50 to 120 μmol / l), but it also depends on factors such as muscle mass, physical activity, age, gender and kidney function. It is important for the assessment of renal function that the creatinine value does not rise above 50% until the Glomerular Filtration Rate (GFR) is reduced, or only then becomes significant. Thus, a "normal" creatinine value does not exclude a beginning kidney insufficiency.
In laboratory medicine, the determination of creatinine excretion (creatinine clearance) is used to calculate the GFR. Creatinine is not reabsorbed by the tube, meaning that virtually every filtered molecule ultimately appears in the urine. Since the plasma concentration of creatinine is not constant (see above), in addition to the 24-h urine collection a venous blood sample is needed to make accurate statements about the GFR.
A simpler but less accurate estimation of GFR is given by the sole determination of the plasma creatinine concentration. In doing so, one makes use of a nonlinear relationship between GFR and the concentration in the blood plasma. Gender, age and body weight are also included in the formula of Donald W. Cockcroft and Henry Gault (Cockcroft-Gault formula), as well as in the more recent ones by Mawer, Björnsson, Hull and Martin. The MDRD formula, developed in 1999 by the Modification of Diet in Renal Disease Study Group (MDRD), refrains from including body weight. In children, the Schwartz formula is well suited for determining GFR.
Also drugs can influence the creatinine level, this is increased for example by opiates and diuretics. Unlike creatine, creatinine is completely meaningless for muscle growth.
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