CRA-Quiz

Quiz: Modification of Dose Descriptors to Correct Starting Point

Little Pro on 2016-08-11 Views:  Update:2018-04-02

This is the answer to the quiz on how to modify dose descriptors to a correct starting point. The original quiz and tutorial can be accessed here.

Answer

Q1: Is modification of dose descriptor necessary if using oral NOAEL (rat)  to derive DNELs for oral route for general population?

  • Yes.
  • No
  • It depends. If there is no difference in oral absorption rate between rats and humans, there is no need to modify dose descriptors. (answer)

Explanation: Modification of dose descriptors is only necessary if there are bioavailablity differences(absorption) between animals and humans, differences in exposure units (e.g, mg/kg bw/d or mg/m3), differences in exposure conditions between animals and humans and differences in respiratory volume (for inhlation route only).

Q2: Is modification of dose descriptor necessary if using inhalatory NOAEC (rat)  to derive DNELs for inhalation route for workers and general population?

  • Yes. (answer)
  • No. 
  • It depends. If there is no difference in absorption rate between rats and humans, there is no need to modify dose descriptors. 

Explanation: Exposure conditions are different between rats and humans. (6h/d for rat, 8h/d for workers and 24h/d for general population). 

Q3: What is corrected dose descriptor (NOAEL) for deriving DNELs for oral route for humans based on the the following data?

  • Dermal NOAEL(rat) from a repeated dose toxicity study =50mg/kg bw/day.
  • Dermal absorption rate for rat from toxicokinetics study=10%. 

Answer:  10mg/kg bw/day

  • Assuming full absorption rate for target route (100%);
  • Corrected oral NOAEL=dermal NOAEL*ABSdermal-rate/ABSoral-human=50mg/kg bw/day*10%/100%=5mg/kg bw/day.

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