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--- renal_clearance [2026/08/10 08:03] – [Elimination Rate Constant (k<sub>e</sub>)] gary1
+++ renal_clearance [2026/08/10 08:28] (current) – gary1
@@ Line 51: / Line 51: @@
 **filtration fraction = glomerular filtration rate (GFR) / renal plasma flow rate (RPF)**
+=====Example - how long does it take to excrete a meal's worth or uric acid?=====
+  ***normal serum concentrations generally range from 3.4 to 7.2 mg/dL (0.20–0.43 mmol/L) in men**
+  *uric acid poorly crosses cell membranes hence **volume of distribution (Vd) = 0.2-0.3L/lean body weight in kg = 14-21L for an average 70kg adult**
+  *GIT bioavailability of purines is ~60%
+  ***every 1mg of base purines yields roughly 1.2mg of uric acid**
+  *a 300g steak plus a beer gives ~450mg purines of which ~270mg is absorbed and metabolized which gives about 324mg uric acid
+  *assuming 324mg uric acid is absorbed, the expected rise in serum levels would be = 324mg / 17L =  19mg/L = 1.9mg/dL
+  *a renal clearance of 12mL/min for uric acid (upper limit normal range) with serum levels of 10mg/dL would give a uric acid excretion rate of 72mg/hr and thus **take the kidneys several hours to reduce serum uric acid levels back to normal after this spike** (even longer if impaired renal function, concomitant alcohol or a larger intake)