CL⁰CR as a function of age and serum creatinine concentration can be calculated

from the Cockroft and Gault Eq. (15.3):

CL⁰

CR ^{¼ 140  age}

ð

Þ
body weight kg

ð

Þ=72 CCR

ð15:3Þ

where age represents the patient’s age in years and CLCR is creatinine concentration

in serum (mg/dL).

This equation gives creatinine clearance for men, and for women the clearance

can be obtained by multiplying the value by 0.85 to account for the lower skeletal

muscle mass in women. Nevertheless, the search for a better equation to evaluate

kidney function and GFR is still going on for computing drug dosages in diverse

populations (Diao et al. 2021).

Elderly patients with comorbid conditions generally receive multiple drugs on a

daily basis. In majority of these patients, the kidney diseases complicate the admo-

nition of prescription drugs. Hence, family physicians, surgeons, and pharmacists

are always in a dilemma how best to measure renal function and decide drug dose

schedules. Impaired kidney function results in reduced drug clearance, drug accu-

mulation in the body, and risk of ADRs, which could sometimes be life-threatening.

Therefore, over-estimation or under-estimation of kidney function can lead to

inappropriate drug dosing or unnecessary discontinuation of potentially essential

drugs. Serum creatinine-based GFR or creatinine clearance prediction equations

[Modification of Diet in Renal Disease (MDRD) and Cockroft-Gault (CG)] are

important tools for identifying geriatric patients with chronic kidney disease

(CKD) and for selecting proper drug doses in these patients. Serum cystatin-C is

an alternative biomarker for impaired renal function in elderly patients that ranges

between slightly and clearly better than the diagnostic accuracy of creatinine. It is

considered to be a suitable biomarker in elderly, since it is less sensitive to metabolic

and extra renal factors than creatinine. Hojs et al. (2010) did analysis of 234 patients

aged 65-years or older and found that serum creatinine-based formulas had slightly

lower diagnostic accuracy than cystatin C-based formulas using ⁵¹Cr EDTA clear-

ance as a reference standard. The Hoek et al. (2003) formula had the highest

accuracy, whereas the Grubb et al. (2005) formulas showed reasonable accuracy

compared to ⁵¹Cr EDTA clearance (Hoek et al. 2003; Larsson et al. 2004).

15.11 Dose Adjustment Suggestions for Antidepressant Drugs

Commonly Prescribed to Elderly

Depression is the frequently encountered psychiatric disorder among the elderly with

10–20% cases of major depressive disorder and 10% having depressive symptoms

(von Moltke et al. 1993; Barua et al. 2011). In the USA, more than 58 million

Americans are inflicted with mental disorders. Elderly depressed individuals usually

have altered physiological functions from normal ageing and concomitant medical

conditions leading to changes in the metabolic disposition of psychotropic drugs.

Therefore, dose adjustments are required to avoid ADRs. Meta-analysis of

246

M. Bhaskar et al.