The pH of urine, the drug's pKa, and the urine flow rate are vital parameters for drug reabsorption and excretion. Urinary pH varies between 4.6 and 8.0 and is influenced by diet, drug intake, and the patient's pathophysiology. It affects a drug's ionization state and reabsorption. For instance, carbohydrate-rich food produces alkaline urine promoting drug excretion, while proteins and certain medications like ascorbic acid lead to acidic urine enhancing reabsorption.
The pKa of a drug, dictating its ionization level at a specific pH, significantly impacts its reabsorption. Lipophilic substances are extensively reabsorbed, while polar molecules are not. Notably, the reabsorption of drugs with pKa ranging from 3.0 to 8.0 (acidic) or 6.0 to 12.0 (basic) relies heavily on urine pH.
Lastly, urine flow rate also alters reabsorption. While pH-insensitive polar drugs remain unaffected, reabsorption is inversely related to urinary flow for weak acids and bases, which are pH-sensitive. Based on their reabsorption compared to water, drugs can be categorized into two: those with equal or greater reabsorption, like phenobarbital, exhibiting a linear relationship between renal clearance and excretion, and those with lesser reabsorption, such as theophylline, demonstrating a convex curvilinear relationship.
Strategies such as forced diuresis can be employed to enhance drug elimination in instances of toxicity or overdose. Understanding these parameters allows for better prediction of drug reabsorption and designing effective drug elimination strategies.
From Chapter 6:
Now Playing
Pharmacokinetics: Drug Excretion and Clearance
71 Views
Pharmacokinetics: Drug Excretion and Clearance
495 Views
Pharmacokinetics: Drug Excretion and Clearance
163 Views
Pharmacokinetics: Drug Excretion and Clearance
56 Views
Pharmacokinetics: Drug Excretion and Clearance
66 Views
Pharmacokinetics: Drug Excretion and Clearance
48 Views
Pharmacokinetics: Drug Excretion and Clearance
62 Views
Pharmacokinetics: Drug Excretion and Clearance
464 Views
Pharmacokinetics: Drug Excretion and Clearance
43 Views
Pharmacokinetics: Drug Excretion and Clearance
26 Views
Pharmacokinetics: Drug Excretion and Clearance
15 Views
Pharmacokinetics: Drug Excretion and Clearance
29 Views
Pharmacokinetics: Drug Excretion and Clearance
36 Views
Pharmacokinetics: Drug Excretion and Clearance
32 Views
Pharmacokinetics: Drug Excretion and Clearance
21 Views
See More
Copyright © 2025 MyJoVE Corporation. All rights reserved
We use cookies to enhance your experience on our website.
By continuing to use our website or clicking “Continue”, you are agreeing to accept our cookies.