There are earlier posts available on RG, as well as a lot of literature available in public domain on this topic. Attaching some literature and guidelines for your reference here.

Sincere thanks Sir.

Now there is no value of median lethal dose calculation..as it is not necessary and not used further...as per guidelines

As per my knowledge, it is not required anymore for pharmaceutical testing. But, it is still being used for chemicals (pesticides etc.), although work is going on to reduce its use there, but it is not obsolete so far. Giving links/literature from organizations such as OECD/NTP/ECVAM/ECHA/EPA below, showing that the guidelines/information are still there:

- https://www.oecd-ilibrary.org/environment/oecd-guidelines-for-the-testing-of-chemicals-section-4-health-effects_20745788?page=2

- https://ntp.niehs.nih.gov/pubhealth/evalatm/test-method-evaluations/acute-systemic-tox/oral-udp/index.html

- https://eurl-ecvam.jrc.ec.europa.eu/validation-regulatory-acceptance/systemic-toxicity/acute-toxicity

- https://www.epa.gov/pesticide-registration/data-requirements-pesticide-registration

LD50 can you calculate by up and down method (Dixon 1980 ..reference )