Dear Parthiban,

Please read the following text:

Estimation of the dose range and percentage of mortality

An approximate LD50 can be initially determined as a pilot study by a so called ‘staircase method’ using a small number of animals (2 each dose) and increasing

the doses of the drug. Five doses can be chosen for determination of LD50 starting from no death to 100% mortality. For example In the study contained in the attached file, for estimation of LD50 of thymoquinone, 5 doses were given intraperitoneally to 5 groups of rats, 10 in each group. The animals were observed for first 2 hours and then at 6th and 24th hour for any toxic symptoms. After 24 hours, the number of deceased rats was counted in each group and percentage of mortality calculated.

The percentage dead for 0 and 100 are corrected before the determination of probits as under:

Corrected % Formula for 0 and 100% mortality:

For 0% dead: 100(0.25/n)

For 100% dead: 100(n-0.25/n)

The probit values are plotted against log-doses and then the dose corresponding to probit 5, i.e., 50%, is found out. In the present case the Log LD50 is 1.76 and LD50= 57.54 mg/kg.

Calculation of Standard Error (SE) of LD50

The SE of LD50 can be calculated from the following formula:

Approx. SE of LD50= (Log LD84-Log LD16) … (a)

where N is number of animals in each group. The probits of 84 and 16 from Table-1 are 5.99 and 4.01 (Approx. 6 and 4), respectively. The log-LD values for the probits 6 and 4 are obtained from the line on the graph in Figure-1, which in the present case are 1.96 and 1.58 and their antilog are 91.2 and 38.02. Using these values in formula (a) the SE of LD50 is 11.9. Therefore, LD50 of thymoquinone when given

intraperitoneally is 57.54±11.9, with 95% confidence interval of 45.64–69.44.

Summary: Using an excel sheet you plot the probit values (y-axis) against log dose values (x-axis). From this plot you get the dose corresponds to probit 5 (50%). The log is used for the determination of the standard error (SE) as it is shown in equation a.

For more details and examples, please see attached file and the following link:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3702116/

Hoping this will be helpful,

Rafik

Dear  Parthiban Ezhumalai

In definition: In toxicology, the lethal dose or concentration (LD) is an indication of the lethality of a given substance or type of radiation.

1- To calculate lethal concentration using excel sheet please check the manuscript of Paul D. Scotti entitled: Excel Spreadsheet for calculation of “dose 50%. 2013. DOI: 10.13140/2.1.1369.2484. In this manuscript you can download the excel sheet of calculation.

Abstract: The spreadsheet calculates the 50% tissue culture infectious dose, TCID50 (also called the tissue culture dose TCD50), as well as the number of infectious units (IU) per ml from standard tissue culture end-point dilution assays. It can also be used to determine, for example, an LD50 (50% lethal dose) or other “xD50s” for whatever end-point dilution assay is being performed. The spreadsheet was written because a large number of in vitro assays to titrate virus preparations were being regularly carried out and the manual calculations from the data were tedious, time-consuming and prone to the occasional error. 

2-The spreadsheet calculations are based also on the Reed and Muench method (Reed, L.J. & Muench, H., "A simple method of estimating fifty percent endpoints", The American Journal of Hygiene 27, 1938, pp 493–497.

Good luck

Thank you

Marius

thank for you suggestion