Time to Peak for Potassium Extended Release Tablets
Potassium extended release tablets reach peak serum concentrations approximately 4-8 hours after administration, with sustained absorption occurring over this extended timeframe rather than the rapid 1-2 hour peak seen with immediate release liquid formulations. 1
Pharmacokinetic Profile of Extended Release Potassium
Extended release potassium chloride formulations demonstrate delayed absorption characteristics compared to liquid formulations, with approximately 90% of the administered dose absorbed by 4 hours and nearly 100% absorbed by 8 hours after administration 1
The mean absorption efficiency of potassium from extended release solid formulations ranges between 70-90%, similar to liquid formulations, but the rate of absorption is significantly slower 1
Peak serum potassium levels occur considerably later with extended release formulations compared to immediate release liquid KCl, which demonstrates rapid absorption and peak effects within 1-2 hours 2
Clinical Implications for Monitoring
The delayed peak effect of extended release formulations makes them less suitable for acute inpatient hypokalemia correction, where immediate release liquid KCl is preferred due to rapid absorption and predictable serum potassium increases 2
For patients on extended release potassium supplementation, blood sampling at 12 hours after the previous dose provides the most accurate comparison to standard pharmacokinetic data, as serum levels at this timepoint are essentially identical between immediate and extended release formulations 3
The extended absorption profile means that sustained release formulations allow for delayed absorption and peak effects, requiring careful monitoring to prevent both hypokalemia and hyperkalemia in the inpatient setting 4
Comparison with Immediate Release Formulations
Immediate release liquid KCl demonstrates rapid absorption with peak rates occurring within 1-2 hours, making it optimal for inpatient use when rapid correction is needed 2, 1
The primary benefit of extended release formulations is reducing the transient peak lithium serum concentration rather than delaying elimination, which affects absorption but not excretion kinetics 3
Extended release formulations provide more stable serum potassium levels over time but require 4-8 hours to reach therapeutic effect, compared to the 1-2 hour timeframe for immediate release preparations 1