terminal rate constant estimation [NCA / SHAM]

posted by Helmut Homepage – Vienna, Austria, 2022-07-12 19:39 (646 d 16:15 ago) – Posting: # 23130
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Hi Imph,

❝ For the estimation of the terminal rate constant (lambda_z) using the two time tmax method, how do we choose the best number of points once the mono exponential phase has been identified?.


Not sure whether I understand you question… With TTT you get the starting point, then use all others until tlast. However, the TTT method (like any other algorithm) works best for IR formulations but might fail on ‘flat’ profiles (controlled re­lease formulations with flip-flop PK) or on profiles of multiphasic release formulations.
Hence, visual inspection of fits is mandatory.1–4


  1. Schulz H-U, Steinijans VW. Striving for standards in bioequivalence assessment: a review. Int J Clin Pharm Ther Toxicol. 1991; 29(8): 293–8. PMID 1743802.
  2. Sauter R, Steinijans VW, Diletti E, Böhm E, Schulz H-U. Presentation of results from bioequivalence studies. Int J Clin Pharm Ther Toxicol. 1992; 30(7): 233–56. PMID 1506127
  3. Hauschke D, Steinjans V, Pigeot I. Bioequivalence Studies in Drug Development. Chichester: Wiley; 2007. p. 131.
  4. Scheerans C, Derendorf H, Kloft C. Proposal for a Standardised Identification of the Mono-Exponential Ter­mi­nal Phase for Orally Administered Drugs. Biopharm Drug Dispos. 2008; 29(3): 145–57. doi:10.1002/bdd.596.

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