ColumnsTwo Clinically Important but Underutilized and Misunderstood Tools: Formulas to Estimate Creatinine Clearance and Therapeutic Drug MonitoringPRESKORN, SHELDON H. MDAuthor Information PRESKORN: Kansas University School of Medicine-Wichita, Wichita, KS Over his 40-year career, S.H.P. has worked with over 140 pharmaceutical and biotech companies in the United States and throughout the world. Over the past year, he has received grants/research support from or has served as a consultant, on the advisory board, or on the speaker’s bureau for Alkermes, BioXcel, Eisai, Janssen, National Institute of Mental Health, Sunovion, and Usona Institute. All clinical trial and study contracts were with and payments made to the Kansas University Medical Center Research Institute, a research institute affiliated with Kansas University School of Medicine-Wichita. Please send correspondence to: Sheldon H. Preskorn, MD, Kansas University School of Medicine, 1010 N. Kansas, Wichita, KS 67217. Journal of Psychiatric Practice: July 2020 - Volume 26 - Issue 4 - p 305-308 doi: 10.1097/PRA.0000000000000471 Buy Metrics Abstract This column first reviews 2 key equations that are central to clinical pharmacology. Clinicians can use the first equation to predict the effect of a specific dose of a specific drug in specific circumstances on the basis of 3 variables: (1) the drug’s pharmacodynamics, (2) the drug’s pharmacokinetics, and (3) biological variance in the individual patient. Clinicians can use the second equation to determine the concentration of a drug that a patient will achieve on a given dose depending on the patient’s ability to clear the drug from the body. These 2 equations allow prescribers to predict whether the dose of a drug a patient is receiving is likely to achieve the desired clinical response (not so low that it is clinically ineffective or so high that it causes adverse effects that interfere with the patient’s ability to tolerate or benefit from the treatment). The author then describes 2 tools clinicians can use to determine a patient’s ability to clear a drug from the body, and thus calculate the concentration of the drug using Equation 2. These tools are: (1) estimation of creatinine clearance and (2) therapeutic drug monitoring. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.