I need calculation for defining LOD, LOQ and liniarity range from Cmax value of drug with suitable example.
Dear Sharad Medhe
"The lower limit of quantitation should be 1/20 of Cmax or lower, as pre-dose concentrations should be detectable at 5% of Cmax or lower (see section 4.1.8. Carry-over effects)."
http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2010/01/WC500070039.pdf
Other requirements see tables in document below:
https://www.fda.gov/downloads/drugs/guidances/ucm070107.Pdf
ULOQ should be calculated based on expected Cmax + RSD% of this value. So if your Cmax is 100 ng/ml and variability for Cmax is 35% then your "safe" ULOQ should be 140-150 ng/ml.
Of course if possible LLOQ should be calculated not only based on Cmax. Key is expected last observed concentration Clast minus RSD% of this value. So if your Clast is 10 ng/ml and variability for Cmax is 25% then your "safe" LLOQ should be 5.0-7.5 ng/ml.
Nice document related to LOD calculations (not for PK) was published by EC:
https://ec.europa.eu/jrc/sites/jrcsh/files/lod_loq_guidance_document_food_contaminants_2016.pdf
Traditional approach is published for example by Agilent and based on S/N ratio.
https://www.agilent.com/cs/library/primers/public/5990-5140EN.pdf
Best regards
Tomasz
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