Phenytoin (PHT) and valproic acid (VPA) compete for the same binding sites on albumin. In patients taking both PHT and VPA, the free fraction of phenytoin will be increased, which causes a total PHT level to falsely represent a patient’s active PHT status.
To supplement the recent video on Total vs. Free Phenytoin and the existing correction calculator for hypoalbuminemia, a new correction calculator for concurrent valproic acid has been released.
MIC breakpoints for antimicrobials are not easy to look up — until now.
CLSI, the governing body in the United States for breakpoints, hides their data behind a $250+ book called M100. For clinicians who do not work in a microbiology lab or have access to the M100 book, it is difficult to find published breakpoints for antimicrobial agents. Continue reading
Now available on ClinCalc – sample size and post-hoc power calculators!
Sample Size Calculator
Prior to designing a trial, authors must determine how many subjects should be included in a trial in order to have adequate statistical power. There are a variety of different equations depending on the trial design and the type of outcome being measured. Check out the ClinCalc Sample Size Calculator.
Post-hoc Power Calculator
Following the completion of a trial, authors (or reviewers) may want to calculate the statistical power of a trial. Although there are pitfalls in using post-hoc power analysis, which are described in the article, post-hoc power is commonly used in medical literature. Check out the ClinCalc Post-hoc Power Calculator. Continue reading
Converting between equianalgesic opioid dosing isn’t exactly a hard science. Given the lack of blinded trials, bidirectional conversions, dose-dependent conversions, incomplete cross-tolerance, equianalgesic discrepancies in the literature, and patient-specific factors (specifically metabolism and absorption), a “simple” equianalgesic conversion table often doesn’t do the process justice. Continue reading
ICU Trials, a mobile app outlining some of the most landmark clinical trials in critical care, is now available for iPhone and Android! Come check out the features and screenshots in all their glory at the ICU Trials for ClinCalc website.
Update March 29, 2014: Vancomycin Calculator for Android and iPhone had received a significant upgrade in both user interface and functionality. Due to developer time and cost, the lite version has been removed from both markets and the paid version price has increased to $2.99. See all the features of the mobile Vancomycin Calculator by clicking here.
Dosing weight-based medications in obese patients can often be a tricky proposition. Most medications do not have guidelines for morbidly obesity, forcing clinicians to pursue in-depth literature searches in order to decide on a dose. This is not only time consuming, but not having an accurate idea of how to dose a medication can be a problem with patient safety.
For the newest addition to ClinCalc, I have created a Drug Dosing in Obesity Reference Table page that will serve as a dynamic growing repository of evidence-based recommendations regarding medication dosing in obese patients. Enjoy! Continue reading
Aminoglycosides have a narrow therapeutic window necessitating therapeutic drug monitoring for safe and effective use. Either fortunately or unfortunately, their use has fallen out of favor and many clinicians are now less familiar with dosing these agents. Combining unfamiliarity with complex pharmacokinetic calculations, the risk of medication errors with aminoglycosides is extremely high. For these reasons, I have developed a new addition to ClinCalc — the aminoglycoside calculator. Continue reading
Ideal body weight and other body weight measures are widely used for a variety of medical purposes, including drug dosing, renal function, categorizing obesity, and dosing chemotherapy. The newest ClinCalc, the Ideal Body Weight Calculator, is capable of providing results and equations for the following body weight metrics:
Evaluating renal function for the purposes of drug dosing is a common task for clinical pharmacists, but a number of misconceptions have developed over the past forty years as the process of evaluating renal function has improved. The following are the top 10 facts that every clinician should know about creatinine clearance:
